| the source and characteristics of chemiluminescence associated with the oxygenase reaction catalyzed by mn(2+)-ribulosebisphosphate carboxylase. | we confirm the observation of mogel and mcfadden (mogel, s.n., and mcfadden, b. a. (1990) biochemistry 29, 8333-8337) that ribulosebisphosphate carboxylase/oxygenase (rubisco) exhibits chemiluminescence while catalyzing its oxygenase reaction in the presence of mn2+. however, our results with the spinach and rhodospirillum rubrum enzymes differ markedly in the following respects. 1) chemiluminescence intensity was directly proportional to enzyme concentration and behaved as if representing the r ... | 1993 | 8314755 |
| on the function of subunit psae in chloroplast photosystem i. | treatment of thylakoids from spinach with nascn removes extrinsic stroma-exposed subunits of the photosystem i complex in addition to cf1 and some other surface proteins. by increasing the nascn concentration, psae is released first, followed by psad and psac. at 0.5 m nascn, about 80% of psae is resolved without significant loss of other ps i polypeptides. time-resolved fluorescence spectroscopy showed no significant alteration of ps i isolated from membranes thus treated with regard to energy ... | 1993 | 8318519 |
| the role and properties of the iron-sulfur cluster in escherichia coli dihydroxy-acid dehydratase. | dihydroxy-acid dehydratase has been purified from escherichia coli and characterized as a homodimer with a subunit molecular weight of 66,000. the combination of uv visible absorption, epr, magnetic circular dichroism, and resonance raman spectroscopies indicates that the native enzyme contains a [4fe-4s]2+,+ cluster, in contrast to spinach dihydroxy-acid dehydratase which contains a [2fe-2s]2+,+ cluster (flint, d. h., and emptage, m. h. (1988) j. biol. chem. 263, 3558-3564). in frozen solution, ... | 1993 | 8325851 |
| analysis of cleavage-site patterns in protein precursor sequences with a perceptron-type neural network. | a method for feature extraction from protein sequences has been developed which is based on an artificial neural filter system. amino acid sequences are analyzed with regard to physicochemical residue properties. this alternative representation of a sequence allows an interpretation of the networks' weight values in a comprehensive and biochemically meaningful way by displaying the optimized network weights in hinton diagrams. signal peptidase cleavage sites of e.coli periplasmic proteins, human ... | 1993 | 8343174 |
| determination of a functional lysine residue of a plant cysteine synthase by site-directed mutagenesis, and the molecular evolutionary implications. | comparison of seven deduced amino acid sequences of cysteine synthase (o-acetyl-l-serine (thiol)-lyase, ec 4.2.99.8) from plants and bacteria disclosed the presence of 12 conserved lys residues, which can be candidates for a functional binding site for pyridoxal phosphate cofactor. these 12 conserved lys residues in a cdna clone encoding spinach cysteine synthase a were replaced with gly by oligonucleotide-directed in vitro mutagenesis. these lys-->gly mutated cdnas were transferred into escheri ... | 1993 | 8344414 |
| high levels of photosystem i subunit ii (psad) mrna result in the accumulation of the psad polypeptide only in the presence of light. | the light-regulated mrna and polypeptide accumulation of the nuclear encoded subunit ii (psad) of the photosystem i reaction center was studied during the greening of etiolated spinach seedlings. upon exposure to continuous white light, the mrna, detected at low levels in etiolated seedlings, accumulated in a specific pattern. in contrast, the psad subunit could not be detected in the etiolated seedlings; the polypeptide could first be detected in thylakoid membranes approximately 4 h after expo ... | 1993 | 8344902 |
| forward electron transfer from phylloquinone a1 to iron-sulfur centers in spinach photosystem i. | forward electron transfer at room temperature from the secondary acceptor a1 (phylloquinone) to the iron-sulfur centers fx, fb, and fa was studied by flash-absorbance spectroscopy in different photosystem i (psi) preparations in order to resolve the controversy concerning the kinetics of a1-reoxidation during forward electron transfer [half times of 15 ns [mathis, p., & sétif, p. (1988) febs lett. 237, 65-68] and 200 ns [brettel, k. (1988) febs lett. 239, 93-98] were reported for psi particles f ... | 1993 | 8347589 |
| tissue- and stage-specific modulation of rna editing of the psbf and psbl transcript from spinach plastids--a new regulatory mechanism? | the psbe operon of spinach chloroplasts, which includes the genes psbe, psbf, psbl and psbj, encodes two rna editing sites. one site corresponds to the initiation codon of the psbl transcript, as has been described earlier for the homologous transcript from tobacco, while at a second editing site, newly reported here, an internal phenylalanine codon of the psbf transcript is restored. both these sites were investigated with respect to the extent of editing in spinach plastids at various developm ... | 1993 | 8355656 |
| isolation and characterization of a new ribosomal protein from the thermophilic eubacteria, thermus thermophilus, t. aquaticus and t. flavus. | a ribosomal protein, showing no homology with other known prokaryotic ribosomal proteins, was isolated and characterized from the thermophilic eubacteria, thermus thermophilus, t. aquaticus and t. flavus. this small (26 amino acids) and strongly basic (1 acidic and 13 basic residues) protein displayed the same primary structure from all three sources. interestingly, it shows about 65% homology with a ribosomal protein from spinach chloroplasts (j. schmidt, personal communication). | 1993 | 8357533 |
| limited proteolysis of chloroplast glyceraldehyde-3-phosphate dehydrogenase (nadp) from spinacia oleracea. | the structural and functional properties of chloroplast glyceraldehyde-3-p-dehydrogenase i (d-glyceraldehyde-3-phosphate: nadp oxidoreductase (phosphorylating) ec 1.2.1.13) from spinacia oleracea were investigated by limited proteolysis. the enzyme is insensitive to trypsin and chymotrypsin, while staphylococcus aureus v8 protease cleaves the c-terminal region of its subunits. subunit a (36 kda) is only partially cleaved at glu 317. no intact subunit b (39 kda) is found at the end of the proteol ... | 1993 | 8357535 |
| amplification of ribulose biphosphate carboxylase/oxygenase large subunit (rubisco lsu) gene fragments from thiobacillus ferrooxidans and a moderate thermophile using polymerase chain reaction. | southern blot analysis of dna from an iron-oxidising moderate thermophile nmw-6 and from thiobacillus ferrooxidans strain tfi-35 demonstrated sequences homologous to the rubisco lsu gene of synechococcus. dna fragments (457 bp) encoding part of the rubisco lsu gene (amino acids 73-200) were amplified from the genomic dna of thiobacillus ferrooxidans and the moderate thermophile nmw-6 using the polymerase chain reaction (pcr) technique (saiki et al. (1985) science 233, 1350-1354). a comparison wi ... | 1993 | 8357616 |
| crystal structure of activated tobacco rubisco complexed with the reaction-intermediate analogue 2-carboxy-arabinitol 1,5-bisphosphate. | the crystal structure of activated tobacco rubisco, complexed with the reaction-intermediate analogue 2-carboxy-arabinitol 1,5-bisphosphate (cabp) has been determined by molecular replacement, using the structure of activated spinach rubisco (knight, s., andersson, i., & brändén, c.-i., 1990, j. mol. biol. 215, 113-160) as a model. the r-factor after refinement is 21.0% for 57,855 reflections between 9.0 and 2.7 a resolution. the local fourfold axis of the rubisco hexadecamer coincides with a cr ... | 1993 | 8358296 |
| the psi-k subunit of photosystem i from barley (hordeum vulgare l.). evidence for a gene duplication of an ancestral psi-g/k gene. | photosystem i of barley contains a polypeptide with an apparent molecular mass of 7 kda when isolated using the detergent n-decyl-beta-d-maltopyranoside. the 7-kda polypeptide is lost from the ps i complex isolated using triton x-100. the 7-kda polypeptide and a corresponding full-length cdna clone have been isolated. based on high sequence similarity to an n-terminal sequence of psi-k from spinach and to the deduced amino acid sequence of psak from chlamydomonas reinhardtii the 7-kda barley pol ... | 1993 | 8360180 |
| comparative oxidative rates of methionine hydroxy analogue in rat and chicken kidney. | 1. l-2-haox a and l-2-haox b were purified from chicken and rat kidney with purification factors of 550 and 45, respectively. 2. it was established that both enzymes were tetrameric (m(r) = 169,000) and consisted of 40 kda monomers. 3. while chicken kidney l-2-haox a is n-terminally blocked like spinach glycolate oxidase and chicken liver l-2-haox a, l-2-hoax b begins with a pro residue. 4. the kinetic parameters of l-hmb oxidation by l-2-haox a and b were determined. 5. the results are particul ... | 1993 | 8365106 |
| identification of an uncleavable targeting signal in the 70-kilodalton spinach chloroplast outer envelope membrane protein. | a cdna clone encoding a cognate 70-kda heat shock protein from the spinach chloroplast outer envelope (sce70) was recently characterized (ko, k., bornemisza, o., kourtz, l., ko, z. w., plaxton, w. c., and cashmore, a. r. (1992) j. biol. chem. 267, 2986-2993). initial studies revealed that sce70 is targeted to the chloroplast outer envelope membrane without further processing. to determine whether sce70 possesses a "targeting domain," we tested the targeting ability of sce70 proteins with various ... | 1993 | 8366085 |
| a role for the epsilon-amino group of lysine-334 of ribulose-1,5-bisphosphate carboxylase in the addition of carbon dioxide to the 2,3-enediol(ate) of ribulose 1,5-bisphosphate. | earlier structural and functional studies of ribulose-1,5-bisphosphate carboxylase/oxygenase imply that k334 facilitates the addition of gaseous substrate to the 2,3-enediol(ate) derived from ribulose 1,5-bisphosphate. crystallographic analysis of the activated spinach enzyme [knight et al. (1990) j. mol. biol. 215, 113-160] shows that the lysyl side chain is appropriately positioned to stabilize the transition state for the addition of co2 to the enediol(ate). furthermore, despite total impairm ... | 1993 | 8369274 |
| analysis of chimeric spinach/cyanobacterial cp43 mutants of synechocystis sp. pcc 6803: the chlorophyll-protein cp43 affects the water-splitting system of photosystem ii. | mutants of the cyanobacterium synechocystis sp. pcc 6803 have been generated in which parts of psbc (the gene encoding the photosystem ii chlorophyll-protein cp43) have been replaced with the homologous gene fragment from spinach. upon the replacement of all but the 3' 84 bp of the cyanobacterial psbc gene with the homologous fragment from spinach, an obligate photoheterotrophic mutant was generated. two photoautotrophic derivatives of this mutant were made reincorporating 3' cyanobacterial sequ ... | 1993 | 8369339 |
| topographical organization of cytochrome b6 in the thylakoid membrane of spinach chloroplasts determined by fluorescence studies with n-cyclohexyl-n'-[4-(dimethylamino)naphthyl]carbodiimide. | in a recent study [wang & beattie (1992) biochemistry 31, 8445-8459], we reported that dicyclohexylcarbodiimide (dccd) was bound to either aspartate-155 or glutamate-166 localized in an amphiphilic, non-membrane-spanning, helix of cytochrome. moreover, dccd inhibits proton translocation in a cytochrome bf complex reconstituted into proteoliposomes without significant inhibition of electron transfer, suggesting that the helix containing aspartate-155 and glutamate-166 may play a role in proton mo ... | 1993 | 8373766 |
| pulse radiolysis and related studies on the ru-modified his 16 derivative of anabaena variabilis [2fe-2s] ferredoxin. | the preparation and characterisation of a ru-modified derivative of the [2fe-2s] ferredoxin fdi component of a. variabilis by attachment of ru(nh3)5 to a surface histidine has been carried out. metal analyses by icp gave an fe/ru ratio of 1.97:1. from nmr the attachment is confirmed as a modification at his-16 and not his-92. no ru-modification of the [2fe-2s] fdi component of spinach, which has his-92 but no his-16, was observed. histidine pka values have been determined and anomalously low val ... | 1993 | 8373814 |
| expression of the potato tuber adp-glucose pyrophosphorylase in escherichia coli. | cdna clones encoding the putative mature forms of the large and small subunits of the potato tuber adp-glucose pyrophosphorylase have been expressed separately and together in an escherichia coli b mutant deficient in adp-glucose pyrophosphorylase activity. expression of both subunits from compatible vectors resulted in restoration of adp-glucose pyrophosphorylase activity. maximal enzyme activity required both subunits. the expressed adp-glucose pyrophosphorylase was purified and characterized. ... | 1993 | 8380404 |
| structural organization of the iron-sulfur centers in synechocystis 6803 photosystem i. epr study of oriented thylakoid membranes and analysis of the magnetic interactions. | the structural properties of the iron-sulfur centers of photosystem i (psi) from the cyanobacterium synechocystis 6803 have been investigated by epr spectrometry. the stoichiometry of centers a, b, and x, determined by epr intensity measurements, gives direct evidence for center x being a [4fe-4s] center in the native system and for the core reaction center protein being a dimer. the directions of the magnetic axes of centers a, b, and x were accurately determined by epr experiments carried out ... | 1993 | 8380418 |
| nucleotide sequence of the cdna encoding nucleoside diphosphate kinase ii from spinach leaves. | the primary structure of nucleoside diphosphate (ndp) kinase ii, one of the two isozymes found in spinach leaves, has been deduced from its cdna sequence. ndp kinase ii comprises 233 amino acid residues and has a molecular mass of 26,107 da, which is larger than that of the purified ndp kinase ii subunits (18 kda) by about 8 kda, suggesting that ndp kinase ii might be post-translationally processed. homology was found between the sequence of spinach ndp kinase ii, and the sequences of spinach nd ... | 1993 | 8381027 |
| kinetic mechanism and regulation of adp-glucose pyrophosphorylase from barley (hordeum vulgare) leaves. | barley (hordeum vulgare, cv. bomi) leaf adp-glucose pyrophosphorylase (agp) was purified to near-homogeneity, using ammonium sulfate fractionation and heat treatment as well as ion exchange, hydrophobic, and dye-ligand chromatography. the enzyme was found to be composed of two subunit types of 51 and 54 kda, which were recognized by the respective rabbit antibodies against the small and/or large subunit of spinach leaf agp. substrate kinetics and product inhibition studies, carried out in the di ... | 1993 | 8384204 |
| uniformly 14c-labelled plant cell walls: production, analysis and behaviour in rat gastrointestinal tract. | uniformly 14c-labelled primary cell walls (14c-pcw) were purified from suspension-cultured cells of spinach (spinacia oleracea l.) grown in a medium containing d-[u-14c]glucose. the approximate polymer composition of the 14c-pcw preparation (% total 14c) was homogalacturonan 30, rhamnogalacturonan 23, xyloglucan 10, other hemicelluloses 3, cellulose 21, lignin 0, 14c-labelled protein < 3 and [14c]starch < 2. the degree of methyl esterification of the pectic polysaccharides was about 25%. the 14c ... | 1993 | 8384475 |
| transient kinetics of electron transfer from a variety of c-type cytochromes to plastocyanin. | plastocyanin (pc) and its physiological reaction partner cytochrome (cyt) f form a complex which is electrostatically stabilized by interactions between complementary localized charges. we have measured the kinetics of intracomplex electron transfer between several reduced cytochromes and pc using laser flash photolysis. with spinach cyt f and spinach pc, we obtain first-order rate constants, kforward = 2780 s-1 and kreverse = 1050 s-1, for the reversible reaction and a complex dissociation cons ... | 1993 | 8387337 |
| the role of an active-site lysyl residue of spinach phosphoribulokinase as explored by site-directed mutagenesis. | based on selective labeling by atp analogues, lys68 of the calvin cycle enzyme phosphoribulokinase (prk) from spinach has been assigned to the active-site region [miziorko et al. (1990), j. biol. chem. 265, 3642-3647]. the equivalent position is occupied by lysyl or arginyl residues in the prk from both prokaryotic and eukaryotic sources, suggesting a requirement for a basic residue at this location. to examine this possibility, we have replaced lys68 of the spinach enzyme with arginyl, glutamin ... | 1993 | 8387794 |
| evidence for the involvement of psi-e subunit in the reduction of ferredoxin by photosystem i. | of the stroma-accessible proteins of photosystem i (psi) from synechocystis sp. pcc 6803, the psi-c, psi-d and psi-e subunits have already been characterized, and the corresponding genes isolated. pcr amplification and cassette mutagenesis were used in this work to delete the psae gene. psi particles were isolated from this mutant, which lacks subunit psi-e, and the direct photoreduction of ferredoxin was investigated by flash absorption spectroscopy. the second order rate constant for reduction ... | 1993 | 8387913 |
| a proposed pathway of proton translocation through the bc complexes of mitochondria and chloroplasts. | the cytochrome bc complexes of the electron transport chain from a wide variety of organisms generate an electrochemical proton gradient which is used for the synthesis of atp. proton translocation studies with radiolabeled n,n'-dicyclohexylcarbodiimide (dccd), the well-established carboxyl-modifying reagent, inhibited proton-translocation 50-70% with minimal effect on electron transfer in the cytochrome bc1 and cytochrome bf complexes reconstituted into liposomes. subsequent binding studies wit ... | 1993 | 8394319 |
| protein conformational changes in tetraheme cytochromes detected by ftir spectroelectrochemistry: desulfovibrio desulfuricans norway 4 and desulfovibrio gigas cytochromes c3. | the conformational change coupled to the redox processes of two tetraheme cytochromes c3 from bacteria of the genus desulfovibrio have been studied by uv-vis and ftir difference spectroscopy combined with protein electrochemistry. two pairs of equivalent hemes were found in desulfovibrio desulfuricans norway 4 cytochrome c3 by uv-vis spectroelectrochemical redox titration in an optically transparent thin-layer electrochemical cell. in contrast to this, desulfovibrio gigas cytochrome c3 showed a ... | 1993 | 8396427 |
| complementation of escherichia coli unc mutant strains by chloroplast and cyanobacterial f1-atpase subunits. | the genes encoding the five subunits of the f1 portion of the atpases from both spinach chloroplasts and the cyanobacterium synechocystis sp. pcc 6803 were cloned into expression vectors and expressed in escherichia coli. the recombinant subunits formed inclusion bodies within the cells. each particular subunit was expressed in the respective unc mutant, each unable to grow on non-fermentable carbon sources. the following subunits restored growth under conditions of oxidative phosphorylation: al ... | 1993 | 8399279 |
| cdna cloning and expression of cysteine synthase b localized in chloroplasts of spinacia oleracea. | the cdna clones for cysteine synthase b, which is localized in chloroplasts of spinacia oleracea l., were isolated by screening a library with synthetic oligonucleotides encoding a partial peptide sequence of the purified protein. nucleotide sequence analysis revealed an open reading frame encoding a polypeptide of 383 amino acids containing a putative transit peptide of 52 amino acids. a bacterial expression vector of the cdna clone could genetically complement an escherichia coli auxotroph lac ... | 1993 | 8405359 |
| purification and antipathogenic activity of lipid transfer proteins (ltps) from the leaves of arabidopsis and spinach. | two homogeneous proteins active in vitro against the bacterial pathogen clavibacter michiganensis subsp. sepedonicus were obtained from a crude cell-wall preparation from the leaves of columbia wild-type arabidopsis. the n-terminal amino acid sequences of these proteins allowed their identification as lipid transfer proteins (ltp-a1, ltp-a2); the ltp1-a1 sequence was identical to that deduced from a previously described cdna (embl m80566) and ltp-a2 was quite divergent (44% identical positions). ... | 1993 | 8405465 |
| o-acetylserine(thiol)lyase from spinach (spinacia oleracea l.) leaf: cdna cloning, characterization, and overexpression in escherichia coli of the chloroplast isoform. | the last enzymatic step for l-cysteine biosynthesis is catalyzed by o-acetylserine(thiol)lyase (oastl, ec 4.2.99.8) which synthesizes l-cysteine from o-acetylserine and "sulfide." we have isolated and characterized a full-length cdna (1432 bp) from a lambda gt11 library of spinach leaf encoding the complete precursor of the chloroplast isoform. the 1149-nucleotide open reading frame coding for o-acetylserine(thiol)lyase was in the direction opposite that of the lambda gt11 beta-galactosidase gen ... | 1993 | 8424655 |
| large unidentified open reading frame in plastid dna (orf2280) is expressed in chloroplasts. | the chloroplast dna encodes genes for components of photosynthesis and the transcription-translation machinery; a number of unidentified open reading frames (orfs) are also present. to determine whether a large orf in the inverted repeat of chloroplast dna of tobacco (orf2280) encodes a chloroplast protein, a conserved region of the orf was expressed in escherichia coli. an antibody against the orf protein was prepared using the purified fusion protein as an antigen. when incubated with proteins ... | 1993 | 8425053 |
| cloning and expression of distinct nitrite reductases in tobacco leaves and roots. | three tobacco nitrite reductase (nir) cdna clones were isolated using spinach nir cdna as a probe. sequence analysis and southern blot hybridization revealed four genes in tobacco. two of these genes presumably derived from the ancestral species nicotiana tomentosiformis, the other two from the ancestor n. sylvestris. northern blot analysis showed that one gene from each ancestral genome was expressed predominantly in leaves, whilst rna from the other was detected mostly in roots. the accumulati ... | 1993 | 8437565 |
| a chloroplast dna deletion located in rna polymerase gene rpoc2 in cms lines of sorghum. | fertile lines of sorghum (sorghum bicolor) were shown to differ from cytoplasmic male sterile (cms) lines by the presence of a 3.8 kb hindiii chloroplast dna fragment in the former and a smaller (3.7 kb) fragment in the latter. dna/dna hybridization studies showed that these two fragments are homologous. fertile plants from s. versicolor, s. almum, s. halepense, and sorghastrum nutans (yellow indiangrass) also have the 3.8 kb fragment, and cms lines studied containing a1, a2 and a3 cytoplasms ha ... | 1993 | 8437572 |
| purification of calreticulin-like protein(s) from spinach leaves. | in a search for the plant equivalent of calsequestrin or calreticulin, the high capacity, low affinity ca2+ binding proteins of muscle and non-muscle cells thought to play important roles in ca2+ storage, we purified two ca(2+)-binding proteins from spinach leaves. the proteins had apparent molecular weights of 55 and 53 kda. on western blot, they did not react either with anti-rabbit skeletal muscle, anti-dog cardiac muscle calsequestrin or anti-rabbit or anti-rat liver calreticulin antibodies, ... | 1993 | 8439313 |
| erythromycin and 5s rrna binding properties of the spinach chloroplast ribosomal protein cl22. | the spinach chloroplast ribosomal protein (r-protein) cl22 contains a central region homologous to the escherichia coli r-protein l22 plus long n- and c-terminal extensions. we show in this study that the cl22 combines two properties which in e. coli ribosome are split between two separate proteins. the cl22 which binds to the 5s rrna can also be linked to an erythromycin derivative added to the 50s ribosomal subunit. this latter property is similar to that of the e. coli l22 and suggests a simi ... | 1993 | 8441674 |
| subunit iii (psa-f) of photosystem i reaction center of the c4 dicotyledon flaveria trinervia. | an immunological survey of c3, c4 and c3-c4-intermediate flaveria species showed that subunit iii (psaf) of the photosystem i reaction center (psi-rc) is present in all these species. this was confirmed by the isolation of the gene encoding the psi-rc subunit iii (psaf) from flaveria trinervia, the first psaf gene to be isolated from a c4 plant. the deduced amino acid sequence showed a high degree of similarity to the corresponding protein of spinach which is a c3 species. a region of 17 hydroph ... | 1993 | 8443351 |
| identification of the nuclear-encoded chloroplast ribosomal protein l12 of the monocotyledonous plant secale cereale and sequencing of two different cdnas with strong codon bias. | two different cdna clones (scl12-1 and scl12-2) encoding precursors of a chloroplast ribosomal protein with homology to l12 from escherichia coli were isolated from rye leaf cdna libraries and sequenced. the corresponding polypeptide of rye chloroplast ribosomes was identified. the sequences for the mature proteins of m(r) 13,447 and 13,609 share 85% amino acid identity. the mature polypeptide of clone scl12-1 has an amino acid identity of 71%, 72% or 44%, respectively, relative to l12 proteins ... | 1993 | 8448215 |
| cryotoxicity of antifreeze proteins and glycoproteins to spinach thylakoid membranes--comparison with cryotoxic sugar acids. | we have used thylakoids from spinach (spinacia oleracea l.) chloroplasts to test the effects of antifreeze proteins (afp) from the starry flounder (platichthys stellatus; afp-sf) and from the antarctic eel pout (austrolycichthys brachycephalus; afp-ab), and antifreeze glycoproteins (afgp) from the antarctic fish dissostichus mawsoni on biological membranes during freezing. freeze-thaw damage, measured as the release of the lumenal protein plastocyanin from the thylakoid vesicles, was strongly in ... | 1993 | 8452860 |
| characterization of the promoter from the single-copy gene encoding ferredoxin-nadp(+)-oxidoreductase from spinach. | we describe a genomic dna segment from spinach that bears part of the single-copy gene for ferredoxin-nadp(+)-oxidoreductase (fnr) including a 3.4 kb promoter sequence. dissection of this dna segment and its analysis in gus (beta-glucuronidase) gene fusions in transgenic tobacco demonstrated that the promoter differs in structure from all other promoters for thylakoid protein genes studied to date. two regions with light-responsive elements were identified. one is located within the first 118 bp ... | 1993 | 8455561 |
| structure and expression of the nuclear gene coding for the chloroplast ribosomal protein l21: developmental regulation of a housekeeping gene by alternative promoters. | we have cloned and sequenced the nuclear gene of the chloroplast ribosomal protein l21 (rpl21) of spinacia oleracea. the gene consists of five exons and four introns. all introns are located in the sequence which corresponds to the escherichia coli-like central core of the protein. l21 mrna is present in photosynthetic (leaves) and nonphotosynthetic (roots and seeds) plant organs, although large quantitative differences exist. primer extension and s1 nuclease mapping experiments revealed the exi ... | 1993 | 8455634 |
| fermentation and subsequent disposition of 14c-labelled plant cell wall material in the rat. | a 14c-labelled plant cell wall preparation (14c-pcw) produced from spinach (spinacia oleracea l.) cell culture exhibits uniform labelling of the major polysaccharide groups (%): pectins 53, hemicellulose 13, cellulose 21, starch 3. this 14c-pcw preparation has been used in rat studies as a marker for plant cell wall metabolism. metabolism of the 14c-pcw occurred largely over the first 24 h. this was due to fermentation in the caecum. the pectic fraction of the plant cell walls was degraded compl ... | 1993 | 8457526 |
| function of yeast cytoplasmic c1-tetrahydrofolate synthase. | the protein product of the ade3 gene of the yeast saccharomyces cerevisiae has been identified as the cytoplasmic trifunctional c1-tetrahydrofolate (thf) synthase, which possesses 10-formyl-thf synthetase (ec 6.3.4.3), 5,10-methenyl-thf cyclohydrolase (ec 3.5.4.9), and 5,10-methylene-thf dehydrogenase (ec 1.5.1.5) activities. however, it has been suggested that the ade3-encoded c1-thf synthase does not play a role in providing the enzymes involved in the generation of one-carbon intermediates in ... | 1993 | 8464869 |
| the rubisco activase (rca) gene is located downstream from rbcs in anabaena sp. strain ca and is detected in other anabaena/nostoc strains. | a gene encoding ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) activase (rca) was found downstream from the rbclrbcs operon in the heterocystous cyanobacterium anabaena sp. strain ca. two unknown open reading frames were shown to be located between rbcs and rca in strain ca and all the genes, rbclrbcs, orf1, orf2, and rca were in the same transcriptional orientation. the deduced amino acid sequence of the anabaena rubisco activase showed both similarities and differences to the plant ... | 1993 | 8467074 |
| exchange reactions catalyzed by group-transferring enzymes oppose the quantitation and the unravelling of the identify of the pentose pathway. | 1. the distributions and rates of transfer of carbon isotopes from a selection of specifically labelled ketosugar-phosphate substrates by exchange reactions catalyzed by the pentose and photosynthetic carbon-reduction-pathway group-transferring enzymes transketolase, transaldolase and aldolase have been measured using 13c-nmr spectroscopy. 2. the rates of these exchange reactions were 5, 4 and 1.5 mumol min-1 mg-1 for transketolase exchange, transaldolase exchange and aldolase exchange, respecti ... | 1993 | 8477719 |
| genes encoding eleven subunits of photosystem i from the thermophilic cyanobacterium synechococcus sp. | we have isolated the genes encoding 11 photosystem i (psi) subunits from synechococcus sp., from which this reaction center has been crystallized. the recombinant dnas, including psaa, psab, psac, psad, psae, psaf, psai, psaj, psak and psal, were obtained by heterologous hybridization with probes from appropriate cdnas or genes from spinach and synechocystis sp. pcc 6803, or with synthetic oligodeoxyribonucleotides. genes psaa/psab, psaf/psaj and psal/psai are each closely linked. the open readi ... | 1993 | 8486290 |
| a small novel chloroplast ribosomal protein (s31) that has no apparent counterpart in the e. coli ribosome. | higher plant chloroplast ribosomes contain several novel protein components whose homologues are not present in the eubacterial e. coli ribosome, indicating a complex evolution of the chloroplast translational apparatus following the endosymbiotic event. here we describe the isolation and characterization of a new small protein from spinach chloroplast ribosome which has, based on the amino acid sequence and immunological data, no counterpart in the e. coli ribosome. we suggest a nomenclature su ... | 1993 | 8490565 |
| the stomach: a new and powerful oxalate absorption site in man. | new information is provided regarding the site and nature of intestinal oxalate absorption in man. intestinal absorption of oxalate was assessed indirectly from the increase in renal oxalate excretion following gastric administration of 5 mmol. oxalate loads. four different types of loads have been used: sodium oxalate, sodium oxalate plus calcium gluconate, rhubarb and spinach. studies were performed in 6 adult patients on permanent gastric tube feeding for various reasons. gastric emptying was ... | 1993 | 8501776 |
| a comparative laser-flash absorption spectroscopy study of anabaena pcc 7119 plastocyanin and cytochrome c6 photooxidation by photosystem i particles. | laser-flash absorption spectroscopy has been used to investigate the kinetics of electron transfer from reduced cytochrome c6 and plastocyanin, isolated from anabaena pcc 7119, to oxidized p700 in photosystem-i particles isolated from the same cyanobacterium and from spinach. for all metalloproteins and photosystems, the observed rate constant has a non-linear protein-concentration dependence, thus suggesting complex formation preceding electron transfer. plastocyanin and cytochrome c6 have simi ... | 1993 | 8504808 |
| the 110-kda polypeptide of spinach plastid dna-dependent rna polymerase: single-subunit enzyme or catalytic core of multimeric enzyme complexes? | highly purified rna polymerase preparations from spinach chloroplasts contain seven major polypeptides of 150, 145, 110, 102, 80, 75, and 38 kda. i find that rna polymerase activity can be separated under defined conditions into three different fractions by heparin-sepharose chromatography. immunological analysis has shown that the first fraction contains rna polymerase activity associated with all seven major polypeptides, and other studies have shown that some of these polypeptides (150, 145, ... | 1993 | 8516293 |
| the role of cysteine residues of spinach ferredoxin-nadp+ reductase as assessed by site-directed mutagenesis. | to investigate the functional role of the cysteine residues present in the spinach ferredoxin-nadp+ oxidoreductase, we individually replaced each of the five cysteine residues with serine using site-directed mutagenesis. all of the mutant reductases were correctly assembled in escherichia coli except for the c42s mutant protein. c114s and c137s mutant enzymes apparently showed structural and kinetic properties very similar to those of the wild-type reductase. however, c272s and c132s mutations y ... | 1993 | 8518283 |
| transcription termination at the escherichia coli thra terminator by spinach chloroplast rna polymerase in vitro is influenced by downstream dna sequences. | we have investigated the mechanism of transcription termination in vitro by spinach chloroplast rna polymerase using templates encoding variants of the transcription-termination structure (attenuator) of the regulatory region of the threonine (thr) operon of escherichia coli. fourteen sequence variants located within its d(g+c) stem-loop and d(a+t)-rich regions were studied. we found that the helix integrity in the stem-loop structure is necessary for termination but that its stability is not di ... | 1995 | 8524662 |
| epr, electron spin echo envelope modulation, and electron nuclear double resonance studies of the 2fe2s centers of the 2-halobenzoate 1,2-dioxygenase from burkholderia (pseudomonas) cepacia 2cbs. | the 2-halobenzoate 1,2-dioxygenase from burkholderia (pseudomonas) cepacia 2cbs (fetzner, s., müller, r., and lingens, f. (1992) j. bacteriol. 174, 279-290) contains both a ferredoxin-type and a rieske-type 2fe2s center. these two significantly different 2fe2s clusters were characterized with respect to their epr spectra, electrochemical properties (rieske-type cluster with gz = 2.025, gy = 1.91, gx = 1.79, gav = 1.91, em = -125 +/- 10 mv; ferredoxin-type center with gz = 2.05, gy = 1.96, gx = 1 ... | 1995 | 8537340 |
| molecular dissection of the epsilon subunit of the chloroplast atp synthase of spinach. | the gene encoding the epsilon subunit (atpe) of the chloroplast atp synthase of spinacia oleracea has been overexpressed in escherichia coli. the recombinant protein can be solubilized in 8 m urea and directly diluted into buffer containing ethanol and glycerol to obtain epsilon that is as biologically active as epsilon purified from chloroplast-coupling factor 1 (cf1). recombinant epsilon folded in this manner inhibits the atpase activity of soluble and membrane-bound cf1 deficient in epsilon a ... | 1995 | 8539297 |
| 245 ghz high-field epr study of tyrosine-d zero and tyrosine-z zero in mutants of photosystem ii. | a 245 ghz 8.7 t high-field epr study of tyrosine-d (tyrd zero) and tyrosine-z (tyrz zero) radicals of photosystem ii (psii) from synechocystis pcc 6803 was carried out. identical principal g values for the wild-type synechocystis and spinach tyrd zero showed that the two radicals were in similar electrostatic environments. by contrast, the principal g values of the tyrd zero in the d2-his189gln mutant of synechocystis were different from those of the wild-type and spinach radicals and were simil ... | 1996 | 8547247 |
| evidence that spinach leaves express calreticulin but not calsequestrin. | the presence of either calreticulin (cr) or calsequestrin (cs-like proteins in spinach (spinacia oleracea l.) leaves has been previously described. here we report the purification from spinach leaves of two highly acidic (isoelectric point 5.2) ca(2+)-binding proteins of 56 and 54 kd by means of deae-cellulose chromatography followed by phenyl-sepharose chromatography in the presence of zn(2+) (i.e., under experimental conditions that allowed the purification of cr from human liver). on the othe ... | 1995 | 8552722 |
| functional analysis of isolated cpn10 domains and conserved amino acid residues in spinach chloroplast co-chaperonin by site-directed mutagenesis. | the possibilities of independent function of the two chaperonin 10 (cpn10) domains of the cpn10 homologue from spinach chloroplasts and the role of five conserved amino acid residues in the n-terminal cpn10 unit were investigated. recombinant single domain proteins and complete chloroplast cpn10 proteins carrying amino acid exchanges of conserved residues in their n-terminal cpn10 domain were expressed in escherichia coli and partially purified. the function of the recombinant proteins was teste ... | 1995 | 8555447 |
| dietary effect on mixed function p450 1a2 activity assayed by estimation of caffeine metabolism in man. | two studies were performed in order to evaluate cytochrome p450 1a2 mediated caffeine metabolism during different nutritional conditions. 1. in the first study, 23 healthy male non-smokers, mean age 25, changed from a customary mixed diet to a standard diet in 6 days. the 6 day's standard diet was based on bread, potatoes, rice and boiled meat. thus, broccoli, cabbage and other cruciferous vegetables, spinach, leeks, onion, parsley, grapefruit, toasted bread, fried and charcoal grilled food, smo ... | 1995 | 8562120 |
| high-level production of spinach glycolate oxidase in the methylotrophic yeast pichia pastoris: engineering a biocatalyst. | glycolate oxidase (go) is a flavo-enzyme that catalyzes the oxidation of glycolate, and is useful for the biocatalytic production of glyoxylate. we have produced high levels of spinach go in the methylotrophic yeast pichia pastoris (pp), by chromosomal integration of multiple copies of an expression cassette containing the go coding sequence under control of the methanol-inducible alcohol oxidase i promoter. under fermentation conditions, greater than 250 units of go per gram of cells (wet weigh ... | 1995 | 8566780 |
| anti-hyperglycemic effect of some edible plants. | the anti-hyperglycemic effect of 12 edible plants was studied on 27 healthy rabbits, submitted weekly to subcutaneous glucose tolerance tests after gastric administration of water, tolbutamide or a traditional preparation of the plant. tolbutamide, cucurbita ficifolia, phaseolus vulgaris, opuntia streptacantha, spinacea oleracea, cucumis sativus and cuminum cyminum decrease significantly the area under the glucose tolerance curve and the hyperglycemic peak. brassica oleracea var. botrytis, alliu ... | 1995 | 8569244 |
| selenium content of convenience and fast foods in ayrshire, scotland. | selenium concentrations were determined via hydride generation atomic absorption spectrometry in more than 100 convenience and fast foods including 34 vegetarian dishes. the foods were purchased mainly in ayrshire, scotland but some came from other parts of the uk. the results indicate a considerable amount of selenium in certain mushrooms, spinach, fish, offals and chicken-based products. the selenium content of beef- and pork-based products was generally somewhat lower. vegetarians having a su ... | 1995 | 8574861 |
| identification of spinach farnesyl protein transferase. dithiothreitol as an acceptor in vitro. | spinach seedlings were found to contain farnesyl protein transferase. the enzyme is activated by zn2+, but not by mg2+. the ph optimum is approximately 7.0 and maximal activity is obtained at 40-45 degrees c. the apparent km for the farnesyl diphosphate substrate is 7 microm. western blotting of soluble proteins with an antiserum raised against mammalian farnesyl protein transferase demonstrated a specific cross-reactivity with the spinach enzyme. the antiserum preferentially recognises the beta ... | 1995 | 8575428 |
| differential effects of n- and c-terminal deletions on the two activities of rubisco activase. | spinach (spinacea oleracea) leaf ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) activase was subjected to limited proteolysis with trypsin and directed deletions were made by modifying the spinach rubisco activase cdna and expressing the 41-kda isoform in escherichia coli. protein exposed to trypsin displayed a more rapid loss of the ability to promote the activation of decarbamylated rubisco than atp hydrolysis (e.g., 10 and 50% activity remaining, respectively, after 1 h). a series ... | 1996 | 8579356 |
| the spinach atpc and atpd genes contain elements for light-regulated, plastid-dependent and organ-specific expression in the vicinity of the transcription start sites. | run-on assays with isolated nuclei demonstrate that the transcription rates of atpc and atpd (gene products: the cf1 subunits gamma and delta of the chloroplast atp synthase) are comparable in spinach seedlings. however, chimeric gus gene fusions with 5'-flanking regions of the atpc gene direct an approximately 10-fold lower gus level in transgenic tobacco compared with equivalent fragments from the atpd gene. both promoters contain sequences in the vicinity of the respective tata boxes, which a ... | 1996 | 8580971 |
| bone composition and histological analysis of young and aged rats fed diets of varied calcium bioavailability. | the effects of varied calcium bioavailability on bone development (young animal) and bone maintenance (aged animal) were evaluated by the application of bone composition and histologic/histomorphometric techniques. | 1995 | 8586778 |
| spinach chloroplast atp-dependent endopeptidase: ti-like protease. | the soluble fraction of spinach chloroplast was used for purification and characterization of an atp-dependent protease. purification included q sepharose fast flow, hydroxylapatite and fplc superose 6 column chromatography. the isolated enzyme requires atp and mg2+ for stimulation and represents a ubiquitin independent serine protease, containing essential sulphydryl group(s). by using fluorogenic peptides a similarity of chloroplast protease to escherichia coli ti protease was observed. the ch ... | 1996 | 8588875 |
| characterization of a cdna clone encoding 23 kda polypeptide of the oxygen-evolving complex of photosystem ii in rice. | we isolated a cdna for a gene that encodes the 23 kda protein of the oxygen-evolving complex of photosystem ii in rice. the amino acid sequence deduced from the cdna is highly similar (71-60% homology) to those of the analogous genes from wheat, tomato, pea, spinach, tobacco and mustard. the expression of the gene that corresponds to the 23 kda protein was inducible in green organs of mature and immature leaves, stems and young panicles but not inducible in roots. the high level of the transcrip ... | 1995 | 8589938 |
| binding site on pea chloroplast fructose-1,6-bisphosphatase involved in the interaction with thioredoxin. | when we compare the primary structures of the six chloroplast fructose-1,6-biophosphatases (fbpase) so far sequenced, the existence of a poorly conserved fragment in the region just preceeding the redox regulatory cysteines cluster can be observed. this region is a good candidate for binding of fbpase to its physiological modulator thioredoxin (td), as this association shows clear differences between species. using a cdna clone for pea chloroplast fbpase as template, we have amplified by pcr a d ... | 1996 | 8605298 |
| occurrence of silent rna editing in chloroplasts: its species specificity and the influence of environmental and developmental conditions. | we have identified three new c-to-u rna editing sites, one in atpf and two in atpa transcripts from tobacco chloroplasts. two of them lead to amino acid substitutions to restore the conserved amino acid found in the corresponding genes of other plants. however, one editing site in the atpa transcript was found to take place partially at the third base of a serine codon (cuc_ to cuu_), thus not leading to an amino acid substitution. this is the first report of silent editing in chloroplasts. the ... | 1996 | 8605316 |
| distribution of thiols in microorganisms: mycothiol is a major thiol in most actinomycetes. | mycothiol [2-(n-acetylcysteinyl)amido-2-deoxy-alpha-d-glucopyranosyl- (1-->1)-myo-inositol] (msh) has recently been identified as a major thiol in a number of actinomycetes (s. sakuda, z.-y. zhou, and y. yamada, biosci. biotech. biochem. 58:1347-1348, 1994; h. s. c. spies and d. j. steenkamp, eur. j. biochem. 224:203-213, 1994; and g. l. newton, c. a. bewley, t. j. dwyer, r. horn, y. aharonowitz, g. cohen, j. davies, d. j. faulkner, and r. c. fahey, eur. j. biochem. 230:821-825, 1995). since thi ... | 1996 | 8606174 |
| the inhibition of dmba-induced carcinogenesis by neoxanthin in hamster buccal pouch. | neoxanthin, a major carotenoid pigment of spinach, is found in the chloroplast membrane and has an unknown function in plants. neoxanthin inhibited the production of superoxide anions in an artificial xanthine and xanthine oxidase system and depressed dna synthesis in methylcholanthrene (mca)-initiated c3h10t1/2 fibroblasts. in two-stage carcinogenesis experiments, neoxanthin at 0.2 micrograms/0.2 ml inhibited the formation of tumors that were induced sequentially by 7,12-dimethylbenz[a]anthrace ... | 1995 | 8610051 |
| a comparative thermodynamic analysis by laser-flash absorption spectroscopy of photosystem i reduction by plastocyanin and cytochrome c6 in anabaena pcc 7119, synechocystis pcc 6803 and spinach. | a comparative thermodynamic analysis of photosystem i (psi) reduction by plastocyanin (pc) and cytochrome c6 (cyt) has been carried out by laser-flash absorption spectroscopy in the cyanobacteria anabaena pcc 7119 and synechocystis pcc 6803 as well as in spinach. these three organisms have been reported to exhibit different reaction mechanisms [hervas, m., navarro, j. a.. díaz, a., bottin, h., & de la rosa, m. a. (1995) biochemistry, 34, 11321-11326]. whereas the activation free energy for the o ... | 1996 | 8611575 |
| function of the [2fe-2s] cluster in mammalian ferrochelatase: a possible role as a nitric oxide sensor. | ferrochelatase (e.c. 4.99.1.1) is the terminal enzyme of the heme biosynthetic pathway, catalyzing the insertion of ferrous iron into protoporphyrin. in mammals the enzyme contains a labile [2fe-2s] center. although this cluster is absent in all prokaryotic, plant, and yeast ferrochelatases, its destruction or elimination from the mammalian enzyme results in loss of enzyme activity. in the current study we present data which clearly demonstrate that mammalian ferrochelatase is strongly inhibited ... | 1996 | 8611576 |
| mutations of glu92 in ferredoxin i from spinach leaves produce proteins fully functional in electron transfer but less efficient in supporting nadp+ photoreduction. | ferredoxin i in spinach chloroplasts fulfils the role of distributing electrons of low redox potential produced by photosystem i to several metabolic routes, nadp+ reduction being the major output. to investigate the role of glu92, which is conserved in the chloroplast-type ferredoxins, mutations of this residue to either gln, ala or lys were obtained through site-directed mutagenesis. a glu93ala mutant was also designed. the four mutants of ferredoxin i were overproduced in escherichia coli, pu ... | 1996 | 8612617 |
| purification, metal cofactor, n-terminal sequence and subunit composition of a 5-aminolevulinic acid dehydratase from the unicellular green alga scenedesmus obliquus, mutant c-2a'. | 5-aminolevulinic acid dehydratase was purified to apparent homogeneity from scenedesmus obliquus, mutant c-2a', starting with serial affinity chromatography according to wang et al., followed by separation on deae-cellulose de 52, tskgel toyopearl hw-55 and fplc on mono q. the enzyme was purified 117-fold compared with the initial crude soluble enzyme preparation and showed a final specific activity of 9.17 microkat/kg protein at ph 8.2 at a total recovery of 7%. mg2+ was determined to be the me ... | 1996 | 8612634 |
| recombinant human cytochrome p450 1a2 and an n-terminal-truncated form: construction, purification, aggregation properties, and interactions with flavodoxin, ferredoxin, and nadph-cytochrome p450 reductase. | previous work from this laboratory indicated that the n-terminus of recombinant human cytochrome p450 (p450) 1a2 expressed in escherichia coli is blocked (p. sandhu, z. guo, t. baba, m. v. martin, r. h. tukey, and f. p. guengerich, (1994) arch. biochem. biophys. 30, 168 -177). a modification of this construct was done to insert an extra 12 residues containing a thrombin-sensitive site just beyond the most n-terminal hydrophobic segment, and the protein was expressed, purified, and cut with throm ... | 1996 | 8615680 |
| spectroscopic and kinetic properties of a recombinant form of the flavin domain of spinach nadh: nitrate reductase. | the c-terminal 268 residues of the spinach assimilatory nadh:nitrate reductase amino acid sequence that correspond to the flavin-containing domain of the enzyme have been selectively amplified and expressed as a recombinant protein in escherichia coli. the recombinant protein, which was produced in both soluble and insoluble forms, was purified to homogeneity using a combination of ammonium sulfate precipitation, affinity chromatography on 5'-adp-agarose and fplc gel filtration. the purified dom ... | 1996 | 8615685 |
| cloning of the amphibolic calvin cycle/oppp enzyme d-ribulose-5-phosphate 3-epimerase (ec 5.1.3.1) from spinach chloroplasts: functional and evolutionary aspects. | exploiting the differential expression of genes for calvin cycle enzymes in bundle-sheath and mesophyll cells of the c4 plant sorghum bicolor l., we isolated via subtractive hybridization a molecular probe for the calvin cycle enzyme d-ribulose-5-phosphate 3-epimerase (r5p3e)(ec 5.1.3.1), with the help of which several full-size cdnas were isolated from spinach. functional identity of the encoded mature subunit was shown by r5p3e activity found in affinity-purified glutatione s-transferase fusio ... | 1995 | 8616224 |
| carboxyl-terminal processing protease for the d1 precursor protein: cloning and sequencing of the spinach cdna. | a previous study has demonstrated that the carboxyl-terminal (c-terminal) processing protease in spinach for the d1 precursor protein (pdl) of the photosystem ii reaction center is a monomeric protein of about 45 kda. based on the amino acid sequence data of the purified protease, a cdna clone encoding the enzyme has been identified and sequenced, from a spinach green leaf cdna library. in order to determine the 5' end of the transcript, the rapid amplification of cdna end (5'-race) technique wa ... | 1996 | 8616242 |
| spinach chloroplast 0-acetylserine (thiol)-lyase exhibits two catalytically non-equivalent pyridoxal-5'-phosphate-containing active sites. | a synthetic gene encoding the mature spinach- chloroplast o-acetylserine (thiol)-lyase was constructed and expressed in an escherichia coli strain carrying the t7 rna polymerase system. the pure recombinant protein was obtained at high yield (6 mg/l cell culture) using a new purification procedure that includes affinity chromatography on green a agarose. its specific activity was of the order of 1000 u/mg, and its physical properties were similar to those previously reported for the natural enzy ... | 1996 | 8617276 |
| cdnas encoding spinach stromal and thylakoid-bound ascorbate peroxidase, differing in the presence or absence of their 3'-coding regions. | two cdna clones encoding stromal (sap28) and thylakoid-bound (sap22) ascorbate peroxidase were isolated from a spinach cdna library constructed by greening cotyledons. the sap22 and sap28 contained an open reading frame encoding mature protein of 295 and 345 amino acids with calculated molecular mass of 32239 da and 37710 da, respectively, preceded by the common transit peptides of 70 amino acid residues. interestingly, the n-terminal 364 amino acids of sap22 were 100% identical with sap28 excep ... | 1996 | 8617374 |
| monitoring of pesticide residues in human milk, soil, water, and food samples collected from kafr el-zayat governorate. | pesticide residues in human milk and environmental samples from kafr el-zayat governorate in egypt were analyzed. this governorate is located near one of the biggest pesticide factories in egypt. organochlorine and organophosphorus pesticides were monitored, including those that have been prohibited from use in egypt. human milk samples (31 samples) from kafr el-zayat were compared with 11 samples collected from cairo. data were compared with results from studies performed in 1987 and 1990. the ... | 1996 | 8620102 |
| efficient expression of the gene for spinach phosphoribulokinase in pichia pastoris and utilization of the recombinant enzyme to explore the role of regulatory cysteinyl residues by site-directed mutagenesis. | phosphoribulokinase (prk), unique to photosynthetic organisms, is regulated in higher plants by thioredoxin-mediated thiol-disulfide exchange in a light-dependent manner. prior attempts to overexpress the higher plant prk gene in escherichia coli for structure-function studies have been hampered by sensitivity of the recombinant protein to proteolysis as well as toxic effects of the protein on the host. to overcome these impediments, we have spliced the spinach prk coding sequence immediately do ... | 1996 | 8626451 |
| plant calreticulin is specifically and efficiently phosphorylated by protein kinase ck2. | calreticulin isolated from spinach leaves has been specifically phosphorylated in vitro by protein kinase ck2 while animal calreticulin from rabbit liver is not a substrate of this kinase under the same conditions. phosphoserine is the only phosphoamino acid detected. high affinity binding (km = 4.4 microm) and a nearly stoichiometric incorporation of phosphate was determined. partially purified spinach calreticulin is phosphorylated at the same site(s) by a copurifying protein kinase sharing bi ... | 1996 | 8629990 |
| endor and special triple resonance spectroscopy of a1.- of photosystem 1. | the photoaccumulated radical state of the photosystem 1 secondary electron acceptor a1, a1.-, has been studied in spinach and the cyanobacterium anabaena variabilis strain met27 using electron nuclear double resonance (endor) and electron--nuclear--nuclear special triple (st) resonance spectroscopies. spectra of a1.- in both these species are very similar. endor spectra of the phylloquinone anion radical in solvent glass were also obtained. comparison of the spectra of the in vivo and in vitro r ... | 1996 | 8639614 |
| spinach chloroplast rnase p: a putative protein enzyme. | ribonuclease p (rnase p) is the enzyme responsible for endonucleolytically separating the 5'-leader sequence from precursor trna molecules. in bacteria, and in the nuclei and mitochondria of all eukaryotes studied so far, rnase p contains an rna subunit which is necessary for activity in vitro and in vivo. in contrast, we showed earlier that partially-purified rnase p from spinach chloroplasts had physical properties inconsistent with the presence of any rna. we now report that the properties of ... | 1995 | 8643412 |
| comparison of the "rieske" [2fe-2s] center in the bc1 complex and in bacterial dioxygenases by circular dichroism spectroscopy and cyclic voltammetry. | two different types of "rieske" [2fe-2s] clusters have been observed in proteins, one in the bc complexes of the respiratory chain and the other in bacterial dioxygenases. we have compared the circular dichroic (cd) spectra and redox properties of the water soluble fragment of the rieske center of the bovine heart mitochondrial bc1 complex (isf) and of the ferredoxin from benzene dioxygenase in pseudomonas putida ml2 (fdbed). spinach ferredoxin was also measured for comparison. the redox potenti ... | 1996 | 8652534 |
| nutritional support to prevent and treat multiple organ failure. | enteral nutrition (en) has several advantages over parenteral nutrition (pn) for postoperative/posttrauma patients. modern technologies for tube-feeding have made early en possible. jejunal tube-feeding has advantages over gastric tube-feeding: faster metabolic recovery, less vomiting, and less risk of regurgitation and aspiration. immediate or early en stimulates the splanchnic and hepatic circulations, improves mucosal blood flow, prevents intramucosal acidosis and permeability disturbances, a ... | 1996 | 8662138 |
| comparative immunological detection of lipids and carotenoids on peptides of photosystem i from higher plants and cyanobacteria. | photosystem i preparations were obtained from wild-type tobacco nicotiana tabacum var. jwb, three chlorophyll-deficient tobacco mutants: su/su, su/su var. aurea and yellow-green leaf patches of the variegated mutant nc 95, spinacia oleracea and furthermore from the mesophilic cyanobacterium synechococcus pcc 7942 and the thermophilic cyanobacterium synechococcus sp.. peptides from these preparations were analyzed by sds polyacrylamide gel electrophoresis and transferred for detection of bound li ... | 1996 | 8663897 |
| pigment quantitation and analysis by hplc reverse phase chromatography: a characterization of antenna size in oxygen-evolving photosystem ii preparations from cyanobacteria and plants. | photosystem ii, the photosynthetic water-oxidizing complex, can be isolated from both plants and cyanobacteria. a variety of methods have been developed for purification of this enzyme, which can be isolated in several functional and structural forms. knowledge of the pigment content of photosystem ii preparations is important for precise spectroscopic, biochemical, and functional analysis. we have determined pigment stoichiometries in oxygen-evolving photosystem ii preparations from plants and ... | 1996 | 8672481 |
| the redox potentials of flavodoxin from desulfovibrio vulgaris and ferredoxin-nadp+ reductase from spinacia oleracea and their complexes. | | 1996 | 8674686 |
| effects of irrelevant sounds on phonological coding in reading comprehension and short-term memory. | the effects of irrelevant sounds on reading comprehension and short-term memory were studied in two experiments. in experiment 1, adults judged the acceptability of written sentences during irrelevant speech, accompanied and unaccompanied singing, instrumental music, and in silence. sentences varied in syntactic complexity: simple sentences contained a right-branching relative clause (the applause pleased the woman that gave the speech) and syntactically complex sentences included a centre-embed ... | 1996 | 8685391 |
| the conformation of the isoprenyl chain relative to the semiquinone head in the primary electron acceptor (qa) of higher plant psii (plastosemiquinone) differs from that in bacterial reaction centers (ubisemiquinone or menasemiquinone) by ca. 90 degrees. | the conformation and partial electron spin density distribution of the reduced primary electron acceptor (qa-), a plastosemiquinone-9 (pq-9-) anion radical, in photosystem ii protein complexes from spinach as well as free pq-9- in solution have been determined by epr and 1h endor spectroscopies. the data show that the conformation of the isoprenyl chain at c beta relative to the aromatic ring differs by 90 degrees for qa- in higher plant psii versus both types of bacterial reaction centers, rhod ... | 1996 | 8688432 |
| metal binding sites of h(+)-atpase from chloroplast and bacillus ps3 studied by epr and pulsed epr spectroscopy of bound manganese(ii). | the metal binding sites of isolated f1 atpase from spinach chloroplasts (cf1) and from the thermophilic bacterium bacillus ps3 (tf1) have been studied by epr and pulsed epr spectroscopy using mn(ii) as a paramagnetic probe. after dialysis in the presence of edta, purified cf1 retains 0.14 +/- 0.07 mg(ii) and approximately 0.75 +/- 0.25 adp. tf1 retains 0.31 +/- 0.03 mg(ii) and 0.08 +/- 0.01 nucleotide (adp + atp) after the same treatment. supplementing known quantities of mn(ii) to metal-deplete ... | 1996 | 8703962 |
| evidence for the expression of the triosephosphate translocator gene in green and non-green tissue of tomato and potato. | western blot analysis revealed a cross reaction of an antibody against the spinach triosephosphate translocator with 29 kda proteins from envelope membranes of plastids from green and red tomato fruits and also of potato tuber amyloplasts. envelope membranes from potato tubers were isolated from a homogenate of total membranes by isopycnic sucrose density gradient centrifugation. we were able to demonstrate by reverse transcription and sequencing of the pcr product that the mrna for the trioseph ... | 1996 | 8704143 |
| major fruit and vegetable contributors to the main serum carotenoids in the spanish diet. | to identify the main sources of serum carotenoids (lutein, zeaxanthin, lycopene, beta-cryptoxanthin, alpha-carotene and beta-carotene) among the fruits and vegetables in the spanish diet, to be used in the design of food questionnaires and to provide useful information for epidemiological and comparative studies. | 1996 | 8730612 |
| molecular cloning and photoperiod-regulated expression of gibberellin 20-oxidase from the long-day plant spinach. | spinach (spinacia oleracea l.) is a long-day (ld) rosette plant in which stem growth under ld conditions is mediated by gibberellins (gas). major control points in spinach are the later steps of sequential oxidation and elimination of c-20 of c20-gas. degenerate oligonucleotide primers were used to obtain a polymerase chain reaction product from spinach genomic dna that has a high homology with ga 20-oxidase cdnas from cucurbita maxima l. and arabidopsis thaliana heynh. this polymerase chain rea ... | 1996 | 8742334 |
| effects of spinach leaf protein concentrate on the serum cholesterol and amino acid concentrations in rats fed a cholesterol-free diet. | the effects of spinach leaf protein concentrate (sppc) on serum and liver lipid concentrations and on serum free amino acid concentrations were examined in rats fed a cholesterol-free diet containing 2 and 10% fats. the serum total cholesterol, triacylglycerol and phospholipid concentrations in the rats fed an sppc diet containing 2% corn oil were significantly lower than those of the rats fed a corresponding casein diet. when 10% corn oil or lard was used, the serum cholesterol-lowering effect ... | 1995 | 8750207 |