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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 ...19938387794
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 ...19938387913
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 ...19938394319
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 ...19938396427
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 ...19938399279
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 ...19938405359
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). ...19938405465
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 ...19938424655
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 ...19938425053
direct desaturation of intact galactolipids by a desaturase solubilized from spinach (spinacia oleracea) chloroplast envelopes.in plants, polyenoic fatty acids are synthesized by desaturase enzymes which use acyl groups of membrane lipids as substrates. to provide direct 'in vitro' evidence for this reaction, we solubilized envelope membranes from spinach (spinacia oleracea) chloroplasts with triton x-100 to release a membrane-bound n-6 desaturase. in the presence of oxygen and reduced ferredoxin, the solubilized enzyme desaturated a variety of substrates, such as free oleic acid, free erucic acid, 1-oleoyl-sn-glycerol ...19938435075
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 ...19938437565
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 ...19938437572
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, ...19938439313
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 ...19938441674
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 ...19938443351
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 ...19938448215
nucleotide sequence and characterization of a cdna encoding the acetohydroxy acid isomeroreductase from arabidopsis thaliana.the primary structure of acetohydroxy acid isomeroreductase from arabidopsis thaliana was deduced from two overlapping cdna. the full-length cdna sequence predicts an amino acid sequence for the protein precursor of 591 residues including a putative transit peptide of 67 amino acids. comparison of the a. thaliana and spinach acetohydroxy acid isomeroreductases reveals that the sequences are conserved in the mature protein regions, but divergent in the transit peptides and around their putative p ...19938448371
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 ...19938452860
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 ...19938455561
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 ...19938455634
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 ...19938457526
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 ...19938464869
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 ...19938467074
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 ...19938477719
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 ...19938486290
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 ...19938490565
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 ...19938501776
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 ...19938504808
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, ...19938516293
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 ...19938518283
completion of the thioredoxin reaction mechanism: kinetic evidence for protein complexes between thioredoxin and fructose 1,6-bisphosphatase.the activation of chloroplast fructose 1,6-bisphosphatase from spinach and soybean leaves by the two chloroplast thioredoxins isolated from the same plants has been studied. the thioredoxin saturation characteristics (vmax: 0.15-103.2 mumol pi/min per mg enzyme; k0.5: 0.0048-0.84 microm; hill coefficient n: 1.02-3.80) indicate that in addition to the reductive activation by thioredoxin specific complex formation between thioredoxin and fructose 1,6-bisphosphatase is responsible for fine regulati ...19958519798
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 ...19958524662
affinity purification of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit epsilon n-methyltransferase.ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit epsilon n-methyltransferase (protein methylase iii, rubisco lsmt, ec 2.1.1.43) catalyzes methylation of the epsilon-amino group of lys-14 in the large subunit of rubisco. in this paper, an affinity purification procedure for pea (pisum sativum l. cv laxton's progress no. 9) rubisco lsmt is described and characterized. spinach (spinacia oleracea l. cv melody) rubisco, a substrate for pea rubisco lsmt, was immobilized to polyvinylidene ...19958527940
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 ...19958537340
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 ...19958539297
identification of a regulatory phosphorylation site in the hinge 1 region of nitrate reductase from spinach (spinacea oleracea) leaves.purified nitrate reductase (nr) from spinach leaves was phosphorylated in vitro by nr-inactivating kinase on ser-543 which is located in the hinge 1 region between the molybdenum-cofactor and haem-binding domains. phosphorylation of ser-543 allowed nr to be inhibited by the inhibitor, nip. degraded nr preparations in which a proportion of the subunits had lost 45 amino acids from the n-terminus during purification could be phosphorylated by nr kinase on ser-543, but could not subsequently be ful ...19958543031
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 ...19968547247
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 ...19958552722
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 ...19958555447
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 ...19958562120
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 ...19958566780
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 ...19958569244
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 ...19958574861
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 ...19958575428
trace elements in spinach (spinacia oleracea) cultivated in soil fortified with graded levels of iron.trace elements in two varieties of spinach cultivated in soil with different levels of added iron were determined. addition of iron to soil decreased potassium, sodium and magnesium contents in spinach markedly (p < 0.05), while the contents of zinc, manganese and copper in spinach were not significantly altered (p > 0.05). differential behavior of spinach varieties was found in the zinc, manganese and sodium contents.19958577654
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 ...19968579356
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 ...19968580971
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.19958586778
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 ...19968588875
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 ...19958589938
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 ...19968605298
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 ...19968605316
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 ...19968606174
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 ...19958610051
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 ...19968611575
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 ...19968611576
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 ...19968612617
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 ...19968612634
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 ...19968615680
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 ...19968615685
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 ...19958616224
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 ...19968616242
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 ...19968617276
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 ...19968617374
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 ...19968620102
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 ...19968626451
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 ...19968629990
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 ...19968639614
the 41 kda protein component of the spinach chloroplast petd mrna 3' stem-loop:protein complex is a nuclear encoded chloroplast rna-binding protein.spinach chloroplast petd gene encodes subunit iv of the cytochrome b6/f complex. like many chloroplast mrnas, the spinach petd mrna contains a 3'utr stem-loop structure that determines correct 3' processing of the pre-mrna and stability of the mature mrna. rna-protein interactions with this structure may be involved in the regulation of petd mrna processing and/or stability. in this report, a spinach chloroplast 41 kd protein has been identified as a component of the petd mrna 3'stem-loop:protei ...19958643382
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 ...19958643412
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 ...19968652534
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 ...19968662138
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 ...19968663897
ion channel permeable for divalent and monovalent cations in native spinach thylakoid membranes.a cation-selective channel was characterized in isolated patches from osmotically swollen thylakoids of spinach (spinacea oleracea). this channel was permeable for k+ as well as for mg2+ and ca2+ but not for cl-. when k+ was the main permeant ion (symmetrical 105 mm kcl) the conductance of the channel was about 60 ps. the single channel conductance for different cations followed a sequence k+ > mg2+ >/= ca2+. the permeabilities determined by reversal potential measurements were comparable for k+ ...19968672080
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 ...19968672481
the inhibitor protein of phosphorylated nitrate reductase from spinach (spinacia oleracea) leaves is a 14-3-3 protein.the inhibitor protein (ip) that inactivates spinach leaf nadh:nitrate reductase (nr) has been identified for the first time as a member of the eukaryotic 14-3-3 protein family based on three lines of evidence. first, the sequence of an eight amino acid tryptic peptide, obtained from immunopurified ip, matched that of a highly conserved region of the 14-3-3 proteins. second, an authentic member of the 14-3-3 family, recombinant arabidopsis gf14omega, caused inactivation of phospho-nr in a magnesi ...19968674533
the redox potentials of flavodoxin from desulfovibrio vulgaris and ferredoxin-nadp+ reductase from spinacia oleracea and their complexes. 19968674686
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 ...19968685391
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 ...19968688432
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 ...19968703962
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 ...19968704143
an arabidopsis thaliana cdna encoding ps ii-x, a 4.1 kda component of photosystem ii: a bipartite presequence mediates seca/delta ph-independent targeting into thylakoids.higher plant photosystem ii preparations contain a 4.1 kda polypeptide (subunit x) associated with the oxygen-evolving core complex. we describe the isolation of a cdna encoding ps ii-x from arabidopsis thaliana, in which the c-terminal region is highly homologous to partially sequenced ps ii-x from wheat and spinach. the mature protein of 42 residues is preceded by a 74-residue, bipartite presequence similar to those involved in the targeting of nuclear-encoded thylakoid lumen proteins, althoug ...19968706853
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.19968730612
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 ...19968742334
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 ...19958750207
reversible, non-denaturing metal substitution in bovine adrenodoxin and spinach ferredoxin and the different reactivities of [2fe-2s]-cluster-containing proteins.the non-denaturing substitution of cluster iron by other metals was studied in spinach ferredoxin and in bovine adrenodoxin. only some of several metal species tested (cd2+, zn2+, vo2+, mn2+, co2+, ni2+) caused bleaching of the residual visible absorbance and of the epr signals of the reduced ferredoxins. no formation of mixed-metal cluster was observed. the most reactive metal species were cd2+ and zn2+ and cd2+ was found to react also with oxidized adrenodoxin. metal-treated proteins were reso ...19968774731
the function and properties of the iron-sulfur center in spinach ferredoxin: thioredoxin reductase: a new biological role for iron-sulfur clusters.thioredoxin reduction in chloroplasts is catalyzed by a unique class of disulfide reductases which use a [2fe-2s]2+/+ ferredoxin as the electron donor and contain an fe-s cluster as the sole prosthetic group in addition to the active-site disulfide. the nature, properties, and function of the fe-s cluster in spinach ferredoxin:thioredoxin reductase (ftr) have been investigated by the combination of uv/visible absorption, variable-temperature magnetic circular dichroism (mcd), epr, and resonance ...19968784198
primary structure and expression of plant homologues of animal and fungal thioredoxin-dependent peroxide reductases and bacterial alkyl hydroperoxide reductases.higher plants express genes encoding peroxiredoxins of the two-cysteine type. this is concluded from the isolation of cdnas from spinach (spinacia oleracea) and barley (hordeum vulgare cv. gerbel) which are homologous to animal, fungal, and bacterial two-cysteine peroxiredoxins. northern blot analysis indicated the presence of at least one corresponding gene in all angiosperms analyzed suggesting that bas1 is a member of an ubiquitous gene family encoding a protein of fundamental importance in o ...19968790288
identification of residues of spinach thioredoxin f that influence interactions with target enzymes.the necessity for two types of thioredoxins (trx f and m) within chloroplasts of higher plants that mediate the same redox chemistry with various target enzymes is not well understood. to approach this complex issue, we have applied site-directed mutagenesis to the identification of residues of trx f that affect its binding to and selectivity for target enzymes. based upon amino acid sequence alignments and the three-dimensional structure of escherichia coli thioredoxin, putative key residues of ...19968798742
phosphorylated nitrate reductase from spinach leaves is inhibited by 14-3-3 proteins and activated by fusicoccin.nitrate reductase (nr) in leaves is rapidly inactivated in the dark by a two-step mechanism in which phosphorylation of nr on the serine at position 543 (ser543) promotes binding to nitrate reductase inhibitor protein (nip). the eukaryotic 14-3-3 proteins bind to many mammalian signalling components (raf-1, bcr, phosphoinositide 3-kinase, protein kinase c, polyomavirus middle-t antigen and cdc25), and are implicated in the timing of mitosis, dna-damage checkpoint control, exocytosis, and activat ...19968805370
the effect of sulfite on the atp hydrolysis and synthesis activities in chloroplasts and cyanobacterial membrane vesicles can be explained by competition with phosphate.the effect of sulfite on atp synthesis and hydrolysis activities is investigated in spinach chloroplasts and in membrane vesicles from the cyanobacterium synechococcus 6716. sulfite inhibits phenazine methosulfate-mediated cyclic photophosphorylation both in thiol-modulated chloroplasts and in cyanobacterial membranes with hso3- (bisulfite) as the active ionic species. the observed inhibition is not due to inhibition of electron transfer or to uncoupling by sulfite. atp synthesis in cyanobacteri ...19968806722
characterization of the bifunctional mitochondrial processing peptidase (mpp)/bc1 complex in spinacia oleracea.the mitochondrial general processing peptidase (mpp) in plant mitochondria constitutes an integral part of the cytochrome bc1 complex of the respiratory chain. here we present a characterization of this bifunctional complex from spinach leaf mitochondria. the purified mpp/bc1 complex has a molecular mass of 550 kda, which corresponds to a dimer. increased ionic strength results in partial dissociation of the dimer as well as loss of the processing activity. micellar concentrations of nonionic an ...19968807403
effect of food composition on vitamin k absorption in human volunteers.the human vitamin k requirement is not known precisely, but the minimal requirement is often assumed to be between 0.5 and 1 x 10(-6) g/kg body weight. in the present study we addressed the question to what extent circulating vitamin k concentrations are influenced by the form in which the vitamer is consumed. the experimental group consisted of five healthy volunteers who received phylloquinone after an overnight fast. on the first day of three successive weeks the participants consumed 1 mg (2 ...19968813897
c-terminal truncation of spinach chloroplast nad(p)-dependent glyceraldehyde-3-phosphate dehydrogenase prevents inactivation and reaggregation.chloroplast nad(p)-dependent glyceraldehyde-3-phosphate dehydrogenase (nad(p)-gapdh; ec 1.2.1.13) consists of two types of subunits: gapa and gapb, which are rather similar, except that gapb carries an unique c-terminal sequence extension. here, we report evidence that this sequence extension might be responsible for aggregation and dark inactivation of the enzyme in vivo. recently, it had been demonstrated that upon limited proteolysis of the purified 600 kda enzyme, using the staphylococcus au ...19968814230
function, structure and evolution of fructose-1,6-bisphosphatase.the hydrolysis of fructose-1,6-bisphosphate to fructose-6-phosphate is a key reaction of carbohydrate metabolism. the enzyme that catalyzes this reaction, fructose-1,6-bisphosphatase, appears to be present in all forms of living organisms. regulation of the enzyme activity, however, occurs by a variety of distinct mechanisms. these include amp inhibition (most sources), cyclic amp-dependent phosphorylation (yeast), and light-dependent activation (chloroplast). in this short review, we have analy ...19878816077
subcellular localization of spinach cysteine synthase isoforms and regulation of their gene expression by nitrogen and sulfur.subcellular localization and regulation of the spinach (spinacia oleracea) cysteine synthase (o-acetyl-l-serine[thiol]-lyase, ec 4.2.99.8) isoforms (cysa, cysb, and cysc) were determined in transgenic tobacco (nicotiana tabacum) and in spinach cell cultures. the 5' regions of cysb and cysc encoding the chloroplastic (cysb-tp) and the putative mitochondrial (cysc-tp) transit peptide (tp) sequences were fused to a bacterial beta-glucuronidase gene (gus) and expressed in tobacco under the control o ...19968819326
nearest-neighbor analysis of higher-plant photosystem i holocomplex.photosystem 1 (psi) preparations from barley (hordeum vulgare) and spinach (spinacia oleracea) were subjected to chemical cross-linking using the cleavable homobifunctional cross-linkers dithiobis(succinimidylpropionate) and 3,3'-dithiobis(sulfosuccinimidyl-propionate). the overall pattern of cross-linked products was analyzed by the simple but powerful technique of diagonal electrophoresis, in which the disulfide bond in the cross-linker was cleaved between the first and second dimensions of th ...19968819335
interspecies cross-reactivity of a monoclonal antibody directed against wheat chloroplast fructose-1,6-bisphosphatase.the primary structure of several chloroplast fructose-1,6-bisphosphatase (cfbpase) was deduced from dna sequences, but only spinach, pea and rapeseed enzymes have been characterized structurally. we analyzed whether cfbpases from different phylogenetic origin contain a common epitope. to this end a dna fragment of 1200 base pairs encoding 338 amino acid residues of wheat cfbpase (38 kda) was cloned in the expression plasmid pgex-1 in frame with the gene coding for glutathione s-transferase (gt) ...19968832098
cloning and molecular analysis of cdnas encoding three sucrose phosphate synthase isoforms from a citrus fruit (citrus unshiu marc.).three partial cdna clones (psps1, psps2 and psps3) encoding sucrose phosphate synthases (sps) were isolated by reverse transcription (rt)-pcr using first-strand cdna prepared from the leaf or fruit of citrus (citrus unshiu marc.). the nucleotide and deduced amino acid sequences of the three clones showed significant similarities to sps previously isolated in other plants. a full-length, cdna clone, citsps1, was isolated from a fruit (juice sacs and pulp segment) cdna library using one (psps1) of ...19968842155
clastogenic activity of pure chlorophyll and anticlastogenic effects of equivalent amounts of crude extract of indian spinach leaf and chlorophyllin following dietary supplementation to mice.dietary consumption of green vegetables has been associated with protection against mutagenic and clastogenic activity of genotoxicants. chlorophyll, being present in all green plants, had earlier been suggested to be the principal factor involved. mice were administered (i) crude aqueous extract of leaf of indian spinach, beta vulgaris l. var.benghalensis hort., and equivalent amounts of (ii) chlorophyll extracted from the leaf; (iii) purified chlorophyll, (iv) chlorophyllin, a sodium-copper de ...19968844993
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