| alternative mrna splicing of 3'-terminal exons generates ascorbate peroxidase isoenzymes in spinach (spinacia oleracea) chloroplasts. | we have isolated two cdna clones encoding spinach (spinacia oleracea) stromal and thylakoid-bound ascorbate peroxidase isoenzymes [ishikawa, sakai, yoshimura, takeda and shigeoka (1996) febs lett. 384, 289-293]. the gene (apxii) encoding both chloroplastic ascorbate peroxidase isoenzymes was isolated and the organization of the gene was determined. alignment between the cdnas and the gene for chloroplastic ascorbate peroxidase isoenzymes indicates that both enzymes arise from a common pre-mrna b ... | 1997 | 9396722 |
| characterization of nitrate reductase from light- and dark-exposed leaves (comparison of different species and effects of 14-3-3 inhibitor proteins). | nitrate reductase (nr) was extracted and partially purified from leaves of squash (curcurbita maxima), spinach (spinacia oleracea), and three transgenic nicotiana plumbaginifolia leaves in the presence of phosphatase inhibitors to preserve its phosphorylation state. purified squash nr showed activation by substrates (hysteresis) when prepared from leaves in the light as well as in darkness. a 14-3-3 protein known to inhibit phosphorylated spinach nr in the presence of mg2+ decreased by 70 to 85% ... | 1997 | 12223776 |
| three spinach leaf nitrate reductase-3-hydroxy-3-methylglutaryl-coa reductase kinases that are regulated by reversible phosphorylation and/or ca2+ ions. | in spinach (spinacea oleracea l.) leaf extracts, three protein kinases (pki, pkii and pkiii) were identified each of which phosphorylated spinach nitrate reductase on serine-543, and inactivated the enzyme in the presence of nitrate reductase inhibitor, 14-3-3. pkiii was also very active in phosphorylating and inactivating arabidopsis (landsberg erecta) 3-hydroxy-3-methylglutaryl-coenzyme a reductase 1 (hmgr1). pki and pkii phosphorylated hmgr1 more slowly than pkiii, compared with their relativ ... | 1997 | 9245257 |
| the ferredoxin-binding site of ferredoxin: nitrite oxidoreductase. differential chemical modification of the free enzyme and its complex with ferredoxin. | spinach (spinacea oleracea) leaf ferredoxin (fd)-dependent nitrite reductase was treated with either the arginine-modifying reagent phenyl-glyoxal or the lysine-modifying reagent pyridoxal-5'-phosphate under conditions where only the fd-binding affinity of the enzyme was affected and where complex formation between fd and the enzyme prevented the inhibition by either reagent. modification with [14c]phenylglyoxal allowed the identification of two nitrite reductase arginines, r375 and r556, that a ... | 1997 | 9232882 |
| protein phosphorylation as a mechanism for osmotic-stress activation of sucrose-phosphate synthase in spinach leaves. | experiments were performed to investigated the mechanism of sucrose-phosphate synthase (sps) activation by osmotic stress in darkened spinach (spinacia oleracea l.) leaves. the activation was stable through immunopurification and was not the result of an increased sps protein level. the previously described ca(2+)-independent peak iii kinase, obtained by ion-exchange chromatography, is confirmed to be the predominant enzyme catalyzing phosphorylation and inactivation of dephosphoserine-158-sps. ... | 1997 | 9232876 |
| a plant chloroplast glutamyl proteinase. | a glutamyl proteinase was partially purified from percoll gradient-purified spinach (spinacia oleracea) chloroplast preparations and appeared to be predominantly localized in the chloroplast stroma. the enzyme degraded casein, but of the 11 synthetic endopeptidase substrates tested, only benzyloxycarbonyl-leucine-leucine-glutamic acid-[beta]-napthylamide was hydrolyzed at measurable rates. in addition, the enzyme cleaved the oxidized [beta]-chain of insulin after a glutamic acid residue. there w ... | 1997 | 12223739 |
| the two forms of ribulose-1,5-bisphosphate carboxylase/oxygenase activase differ in sensitivity to elevated temperature. | ribulose-1,5-bisphosphate carboxylase/oxygenase activase often consists of two polypeptides that arise from alternative splicing of pre-mrna. in this study recombinant versions of the spinach (spinacea oleracea l.) 45- and 41-kd forms of activase were analyzed for their response to temperature. the temperature optimum for atp hydrolysis by the 45-kd form was 45[deg]c, approximately 13[deg]c higher than the 41-kd form. when the two forms were mixed, the temperature response of the hybrid enzyme w ... | 1997 | 12223718 |
| changes in proteasome levels in spinach (spinacia oleracea) seeds during imbibition and germination. | proteasomes are the major cytosolic protease complexes responsible for energy-dependent and extra-lysosomal proteolysis. ubiquitinated proteins are degraded by the 26s proteasome which is composed of a 20s proteasome and two regulatory complexes. changes in the 20s and 26s proteasome activity levels and protein abundance in spinach seeds during imbibition and germination were examined by using glycerol density gradient centrifugation. the 26s proteasome activity level decreased transiently durin ... | 1997 | 9214761 |
| characterization of 26s proteasome alpha- and beta-type and atpase subunits from spinach and their expression during early stages of seedling development. | three kinds of cdnas encoding 26s proteasome subunits have been cloned from spinach (spinacia oleracea l.). these genes, designated as sopsc8, sopsc1 and soprs7, encode an alpha-type and a beta-type subunit of the 20s catalytic core, and an atpase subunit of the 19/22s regulatory complex, respectively. the deduced protein sequences showed high sequence similarities to other proteasome alpha- and beta-type and atpase subunit proteins. southern blot analysis indicates that there are additional mem ... | 1997 | 9207846 |
| the nitrate reductase gene isolated from dna of cultured spinach cells. | the gene encoding nitrate reductase was cloned from the dna isolated from cultured spinach (spinacia oleracea cv. hoyo) cells and sequenced. the clone contains 7612 nucleotides of the gene which consists of four exons interrupted by three introns. the transcription start site was determined by primer extension analysis and located 193 bp upstream of the atg translation initiation codon. the 5'-flanking region contains a tata box and caat box. | 1997 | 9128133 |
| functional consequences of deletions of the n terminus of the [epsilon] subunit of the chloroplast atp synthase. | the [epsilon] subunit of the chloroplast atp synthase functions in part to prevent wasteful atp hydrolysis by the enzyme. in addition, [epsilon] together with the remainder of the catalytic portion of the synthase (cf1) is required to block the nonproductive leak of protons through the membrane-embedded component of the synthase (cfo). mutant [epsilon] subunits of the spinach (spinacia oleracea) chloroplast atp synthase that lack 5, 11, or 20 amino acids from their n termini ([epsilon]-[delta]5n ... | 1997 | 12223668 |
| enhanced employment of the xanthophyll cycle and thermal energy dissipation in spinach exposed to high light and n stress. | the involvement of the xanthophyll cycle in photoprotection of n-deficient spinach (spinacia oleracea l. cv nobel) was investigated. spinach plants were fertilized with 14 mm nitrate (control, high n) versus 0.5 mm (low n) fertilizer, and grown under both high- and low-light conditions. plants were characterized from measurements of photosynthetic oxygen exchange and chlorophyll fluorescence, as well as carotenoid and cholorophyll analysis. compared with the high-n plants, the low-n plants showe ... | 1997 | 12223645 |
| identification and purification of a spinach chloroplast dna-binding protein that interacts specifically with the plastid psaa-psab-rps14 promoter region. | we have previously shown the presence in chloroplasts of sequence-specific dna-binding proteins that interact specifically with two regions located downstream and upstream from the 5'-transcription start site of the plastid psaa-psab-rps14 operon. as part of an effort to elucidate the regulatory mechanism of plastid transcription during plant development, we report here the purification and characterization of the chloroplast dna-binding protein from spinach (spinacia oleracea l. var. spinosa as ... | 1997 | 9431684 |
| the chloroplast envelope is permeable for maltose but not for maltodextrins. | permeation of [14 c]maltose into the stroma (measured as the sorbitol-impermeable space) of isolated intact spinach (spinacia oleracea l.) chloroplasts was studied using the silicone oil centrifugation technique. maltose uptake showed michaelis menten-kinetics with a k(m) of 25 mm and a vmax of 19.5 mumol maltose. mg chl-1. h-1 at 15 degrees c. lack of interaction of glucose and maltose uptake suggested the presence of individual translocators for maltose and glucose in the inner chloroplast env ... | 1996 | 8980636 |
| greenhouse spinach production in a nft system. | primed spinach (spinacia oleracea l., cv. nordic) seed was started in rockwool slabs in a growth room for eight days before the seedlings were transplanted into a controlled environment greenhouse equipped with five identical, but separate, nft systems. the day and night temperatures in the greenhouse were maintained at 24 and 18 degrees c, respectively, with the daytime starting at 06:00 and ending at 22:00 hr. a photoperiod of 16 hrs was maintained, to prevent early bolting, and different targ ... | 1996 | 11541569 |
| primary structure of the n-linked carbohydrate chains of calreticulin from spinach leaves. | calreticulin is a multifunctional ca(2+)-binding protein of the endoplasmic reticulum of most eukaryotic cells. the 56 kda calreticulin glycoprotein isolated from spinach (spinacia oleracea l.) leaves was n-deglycosylated by pngase-f digestion. the carbohydrate moiety was isolated by gel permeation chromatography and purified by high-ph anion-exchange chromatography. the fractions were investigated by 500 mhz 1h-nmr spectroscopy, in combination with monosaccharide analysis and fast-atom bombardm ... | 1996 | 8981089 |
| carbohydrate and carbon metabolite accumulation responses in leaves of ozone tolerant and ozone susceptible spinach plants after acute ozone exposure. | the objective of this study was to determine whether exposure of plants to ozone (o3) increased the foliar levels of glucose, glucose sources, e.g., sucrose and starch, and glucose-6-phosphate (g6p), because in leaf cells, glucose is the precursor of the antioxidant, l-ascorbate, and glucose-6-phosphate is a source of nadph needed to support antioxidant capacity. a further objective was to establish whether the response of increased levels of glucose, sucrose, starch and g6p in leaves could be c ... | 1996 | 24271929 |
| higher-plant chloroplast and cytosolic fructose-1,6-bisphosphatase isoenzymes: origins via duplication rather than prokaryote-eukaryote divergence. | full-size cdnas encoding the precursors of chloroplast fructose-1,6-bisphosphatase (fbp), sedoheptulose-1,7-bisphosphatase (sbp), and the small subunit of rubisco (rbcs) from spinach were cloned. these cdnas complete the set of homologous probes for all nuclear-encoded enzymes of the calvin cycle from spinach (spinacia oleracea l.). fbp enzymes not only of higher plants but also of non-photosynthetic eukaryotes are found to be unexpectedly similar to eubacterial homologues, suggesting a eubacter ... | 1996 | 8980497 |
| 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 ... | 1996 | 8819335 |
| purification and identification of the violaxanthin deepoxidase as a 43 kda protein. | violaxanthin deepoxidase (vde) has been purified from spinach (spinacia oleracea) leaves. the purification included differential sonication of thylakoid membranes, differential (nh4)2so4 fractionation, gel filtration chromatography and finally either hydrophobic interaction chromatography or anion exchange chromatography. a total purification of more than 5000-fold compared to the original thylakoids enabled the identification of a 43 kda protein as the vde, in contrast to earlier reported molec ... | 1996 | 24271609 |
| 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+ ... | 1996 | 8672080 |
| 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 ... | 1996 | 8674533 |
| 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 ... | 1996 | 8807403 |
| 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 ... | 1996 | 8790288 |
| evidence that isolated chloroplasts contain an integrated lipid-synthesizing assembly that channels acetate into long-chain fatty acids. | high rates of light-dependent fatty acid synthesis from acetate were measured in isolated chloroplasts that were permeabilized to varying extents by resuspension in hypotonic reaction medium. the reactions in hypotonic medium unsupplemented with cofactors were linear with time and were directly proportional to chlorophyll concentration, suggesting that the enzymes and cofactors of fatty acid synthesis remained tightly integrated and thylakoid associated within disrupted chloroplasts. permeabiliz ... | 1996 | 12226255 |
| envelope membranes from spinach chloroplasts are a site of metabolism of fatty acid hydroperoxides. | enzymes in envelope membranes from spinach (spinacia oleracea l.) chloroplasts were found to catalyze the rapid breakdown of fatty acid hydroperoxides. in contrast, no such activities were detected in the stroma or in thylakoids. in preparations of envelope membranes, 9s-hydroperoxy-10(e),12(z)-octadecadienoic acid, 13s-hydroperoxy-9(z),11(e)-octadecadienoic acid, or 13s-hydroperoxy-9(z),11(e),15(z)-octadecatrienoic acid were transformed at almost the same rates (1-2 [mu]mol min-1 mg-1 protein). ... | 1996 | 12226196 |
| guanosine triphosphate-binding proteins on the plasmalemma of spinach leaf cells. | the molecular mechanism of light perception through phytochrome is not well understood. this red-light photosensor has been implicated in various physiological processes, including the photoinduction of flowering. a few recent studies have shown that phytochrome initiates signal transduction chains via guanosine triphosphate (gtp)-binding proteins (g-proteins). we show here by different approaches that g-proteins exist in spinach (spinacia oleracea l. cv. nobel). binding of gtp on the plasmalemm ... | 1996 | 28321666 |
| relationship between photosynthetic electron transport and ph gradient across the thylakoid membrane in intact leaves. | under conditions (0.2% co2; 1% o2) that allow high rates of photosynthesis, chlorophyll fluorescence was measured simultaneously with carbon assimilation at various light intensities in spinach (spinacia oleracea) leaves. using a stoichiometry of 3 atp/co2 and the known relationship between atp synthesis rate and driving force (delta ph), we calculated the light-dependent ph gradient (delta ph) across the thylakoid membrane in intact leaves. these delta ph values were correlated with the photoch ... | 1995 | 11607620 |
| 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 ... | 1995 | 8543031 |
| the function of ascorbic acid in photosynthetic phosphorylation. | ascorbate is oxidized to the free radical monodehydroascorbate by o2.- and by h2o2 (through the action of ascorbate peroxidase) formed in the mehler reaction by isolated spinach (spinacia oleracea) thylakoids. light-dependent electron transport from water to monodehydroascorbate is shown to be coupled to atp formation with a ratio atp:o2 of 2. in the presence of ascorbate the net o2 exchange balance of the mehler reaction is close to zero, and the synthesis of atp is increased 2 to 3 times due t ... | 1995 | 12228662 |
| enzymes of choline synthesis in spinach (response of phospho-base n-methyltransferase activities to light and salinity). | in spinach (spinacia oleracea l.), choline is synthesized by the sequential n-methylation of phosphoethanolamine -> phosphomono- -> phosphodi- -> phosphotrimethylethanolamine (i.e. phosphocholine) followed by hydrolysis to release choline. differential centrifugation of spinach leaf extracts shows that enzymes catalyzing the three n-methylations are cytosolic. these enzymes were assayed in leaf extracts prepared from plants growing under various light/dark periods. under a diurnal, 8-h light/16- ... | 1995 | 12228655 |
| induction of hexose-phosphate translocator activity in spinach chloroplasts. | many environmental and experimental conditions lead to accumulation of carbohydrates in photosynthetic tissues. this situation is typically associated with major changes in the mrna and protein complement of the cell, including metabolic repression of photosynthetic gene expression, which can be induced by feeding carbohydrates directly to leaves. in this study we examined the carbohydrate transport properties of chloroplasts isolated from spinach (spinacia oleracea l.) leaves fed with glucose f ... | 1995 | 12228584 |
| evidence for a novel atp-dependent membrane-associated protease in spinach leaf mitochondria. | we report the presence of an atp-dependent proteolytic activity in spinach (spinacia oleracea) leaf mitochondria. the proteolysis was observed as degradation of newly imported precursor protein. the precursor studied was that of the atp synthase f1 beta subunit of nicotiana plumbaginifolia, transcribed and translated in vitro. degradation of pre-f1 beta was observed during kinetic studies of import in vitro. the degradation was characterized in chase experiments in which the precursor was import ... | 1995 | 7654191 |
| molecular and physiological analysis of a thylakoid k+ channel protein. | transport studies identified a k+ channel protein in preparations of purified spinach (spinacea oleracea) thylakoid membrane. this protein was solubilized from native membranes and reconstituted into artificial proteoliposomes with maintenance of functional integrity. a 33-kd thylakoid polypeptide was identified as a putative component of this thylakoid protein. this identification was made using an antibody raised against a synthetic peptide representing a highly conserved region of k+ channel ... | 1995 | 12228576 |
| spinach leaf sucrose-phosphate synthase and nitrate reductase are phosphorylated/inactivated by multiple protein kinases in vitro. | the regulation of sucrose-phosphate synthase (sps) and nitrate reductase (nr) activities from mature spinach (spinacia oleracea l.) leaves share many similarities in vivo and in vitro. both enzymes are light/dark modulated by processes that involve, at least in part, reversible protein phosphorylation. experiments using desalted crude extracts show that the atp-dependent inactivation of spinach sps and nr is sensitive to inhibition by glucose-6-phosphate. also, a synthetic peptide homolog of the ... | 1995 | 12228528 |
| purification and characterization of an nadh-hexacyanoferrate(iii) reductase from spinach leaf plasma membrane. | plasma membranes were purified from spinach (spinacea oleracea l.) leaves by aqueous two-phase partitioning. the nadh-hexacyanoferrate(iii) reductase was released from the membrane by chaps solubilization and purified 360-fold by ion-exchange chromatography followed by affinity chromatography and size-exclusion chromatography on fplc. a major band of 45 kda and a minor contaminant of 66 kda were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (sds-page). the band at 45 kda ... | 1995 | 7793986 |
| an investigation of the sustained component of nonphotochemical quenching of chlorophyll fluorescence in isolated chloroplasts and leaves of spinach. | the slowly reversible component of nonphotochemical quenching of chl fluorescence, ql, has been investigated in intact leaves and chloroplasts of spinach (spinacia oleracea). in leaves, between 50 and 100% of ql (defined as the quenching that remained after at least 10 min of dark adaptation of a previously illuminated leaf) is instantly reversible when leaves were infiltrated with nigericin. chloroplasts isolated from leaves in which ql had been induced by prior illumination retained the same l ... | 1995 | 12228504 |
| enzymatic evidence for a complete oxidative pentose phosphate pathway in chloroplasts and an incomplete pathway in the cytosol of spinach leaves. | the intracellular localization of transaldolase, transketolase, ribose-5-phosphate isomerase, and ribulose-5-phosphate epimerase was reexamined in spinach (spinacia oleracea l.) leaves. we found highly predominant if not exclusive localization of these enzyme activities in chloroplasts isolated by isopyknic centrifugation in sucrose gradients. glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glucose phosphate isomerase, and triose phosphate isomerase activity was present in t ... | 1995 | 12228497 |
| 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. | 1995 | 8577654 |
| the expression of nuclear genes encoding plastid ribosomal proteins precedes the expression of chloroplast genes during early phases of chloroplast development. | the development of different plant organs (root, hypocotyl, and cotyledons) during seed germination is connected with the transformation of proplastids, which are found in embryonic and meristematic tissues, into amyloplasts in root tissues and into chloroplasts in cotyledons. we have analyzed the expression of nuclear and plastid genes coding for the plastid translational apparatus during the first 7 d of spinacia oleracea development. results show that the nuclear genes (rps1, rps22, rpi21, an ... | 1995 | 7610166 |
| antibodies that distinguish between the serine-158 phospho- and dephospho-form of spinach leaf sucrose-phosphate synthase. | serum antibodies were raised against a synthetic peptide corresponding to the amino acid sequence surrounding the major inactivating phosphorylation site (serine-158) of spinach (spinacia oleracea) leaf sucrose-phosphate synthase (sps). the anti-peptide antibodies precipitated highly activated sps preferentially to atp-inactivated sps and interacted only weakly with the sodium dodecyl sulfate-denatured enzyme bound to a membrane. the antibodies blocked phosphorylation but not dephosphorylation o ... | 1995 | 12228466 |
| biosynthesis and distribution of insect-molting hormones in plants--a review. | insect-molting hormones, phytoecdysteroids, have been reported to occur in over 100 plant families. plants, unlike insects, are capable of the biosynthesis of ecdysteroids from mevalonic acid, and in several cases the biosynthesis of phytoecdysteroids was also demonstrated to proceed via sterols. spinacia oleracea (spinach) biosynthesizes polypodine b and 20-hydroxyecdysone, which is the predominant insect-molting hormone found in plant species. the onset of ecdysteroid production in spinach req ... | 1995 | 7791535 |
| identification of a protein that inhibits the phosphorylated form of nitrate reductase from spinach (spinacia oleracea) leaves. | the low-activity, phosphorylated form of nitrate reductase (nr) became activated during purification from spinach (spinacia oleracea) leaves harvested in the dark. this activation resulted from its separation from an approximately 110-kd nitrate reductase inhibitor protein (nip). readdition of nip inactivated the purified phosphorylated nr, but not the active dephosphorylated form of nr, indicating that the inactivation of nr requires its interaction with nip as well as phosphorylation. consiste ... | 1995 | 12228371 |
| methionine biosynthesis in higher plants. ii. purification and characterization of cystathionine beta-lyase from spinach chloroplasts. | cystathionine beta-lyase, the second enzyme of the transsulfuration pathway leading to homocysteine synthesis was purified over 16,000-fold from spinach (spinacia oleracea l.) leaf chloroplasts (soluble fraction). enzyme activity was followed along the purification scheme by either a colorimetric method for the determination of cysteine or by fluorescence detection of the bimane derivative of l-homocysteine after reverse-phase hplc. cystathionine beta-lyase has a molecular mass of 170,000 +/- 50 ... | 1995 | 7840670 |
| isolation of multiple dimeric forms of phosphoribulokinase from an alga and a higher plant. | dimeric phosphoribulokinase from either spinach (spinacia oleracea) leaf or from the green alga, scenedesmus obliquus can be separated into three distinct forms by hydrophobic interaction chromatography. variation of the redox conditions prior to and during chromatography resulted in specific forms of phosphoribulokinase being eluted. it is suggested that three dimeric forms of phosphoribulokinase differ in the extent of disulfide bond formation between cys-16 and cys-55 in each of the two subun ... | 1994 | 7947971 |
| crystallization and preliminary crystallographic data for acetohydroxy acid isomeroreductase from spinacia oleracea. | acetohydroxy acid isomeroreductase (ec 1.1.1.86) is one of the enzymes involved in branched-chain amino acid biosynthesis. the enzyme from spinach (spinacia oleracea) leaves has been crystallized using the hanging drop vapour diffusion method. the free enzyme crystallized from polymethylene glycol solutions, but these crystals were unsuitable for x-ray diffraction analysis. in the presence of nadph, mg(2+) and a reaction intermediate analogue (2-dimethylphosphinoyl-2-hydroxy acetic acid (hoe 704 ... | 1994 | 7932712 |
| interactions of plant acetohydroxy acid isomeroreductase with reaction intermediate analogues: correlation of the slow, competitive, inhibition kinetics of enzyme activity and herbicidal effects. | n-hydroxy-n-isopropyloxamate (ipoha) is known to inhibit extremely tightly (ki of 22 pm) the bacterial acetohydroxy acid isomeroreductase (ec 1.1.1.86) [aulabaugh and schloss (1990) biochemistry 29, 2824-2830], the second enzyme of the branched-chain-amino-acid-biosynthetic pathway. yet, although the same pathway exists in plant cells, this compound presents only very poor herbicidal action. towards the goal of gaining a better understanding of this behaviour, we have studied the mechanism of in ... | 1994 | 8053906 |
| cdna sequence for the plastidic phosphoglucomutase from spinacia oleracea (l.). | | 1994 | 7972501 |
| ribosomes pause during the expression of the large atp synthase gene cluster in spinach chloroplasts. | the large atp synthase gene cluster from spinach (spinacia oleracea) chloroplasts encodes five genes, the last four of which encode subunits of the atp synthase complex. in preliminary experiments (j.k. kim, m.j. hollingsworth [1992] anal biochem 206: 183-188) it was shown that ribosomes pause during translation of these open reading frames. we have examined ribosome pausing in the four atp synthase open reading frames of this gene cluster to determine whether it could affect the final ratio of ... | 1994 | 7972492 |
| tissue-specific expression of the large atp synthase gene cluster in spinach plastids. | plastids present in different tissues may vary morphologically and functionally, despite the fact that all plastids within the same plant contain identical genomes. this is achieved by regulation of expression of the plastid genome by tissue-specific factors, the mechanisms of which are not fully understood. the proton translocating atp synthase/atpase is a multisubunit complex composed of nine subunits, six encoded in the plastid and three in the nucleus. we have investigated the tissue-specifi ... | 1994 | 8049363 |
| full-length cdna sequences for both ferredoxin-thioredoxin reductase subunits from spinach (spinacia oleracea l.). | full-length cdna clones for ferredoxin-thioredoxin reductase subunits a and b of spinacia oleracea were obtained and their complete nucleotide sequences were determined. the results are compared with other known ftr sequences. | 1994 | 8167141 |
| phosphopantethenylated precursor acyl carrier protein is imported into spinach (spinacia oleracea) chloroplasts. | acyl carrier protein (acp) is an essential cofactor of fatty acid synthase. in plants, acp is synthesized in the cytosol as a larger precursor protein and then is imported into the plastid where it is processed to a smaller mature form. the active form of acp uses a covalently linked 4[prime]-phosphopantetheine prosthetic group derived from coenzyme a to covalently bind the acyl intermediates during fatty acid synthesis. the prosthetic group is added to acp by holoacp synthase. this enzyme activ ... | 1994 | 12232143 |
| purification and kinetic properties of serine acetyltransferase free of o-acetylserine(thiol)lyase from spinach chloroplasts. | serine acetyltransferase, a key enzyme in the l-cysteine biosynthetic pathway, was purified over 300,000-fold from the stroma of spinach (spinacia oleracea) leaf chloroplasts. the purification procedure consisted of ammonium sulfate precipitation, anion-exchange chromatography (trisacryl m deae and mono q hr10/10), hydroxylapatite chromatography, and gel filtration (superdex 200). the purified enzyme exhibited a specific activity higher than 200 units mg-1 and a subunit molecular mass of about 3 ... | 1994 | 12232109 |
| the solute permeability of thylakoid membranes is reduced by low concentrations of trehalose as a co-solute. | the different efficiencies of sucrose and trehalose in protecting isolated spinach (spinacia oleracea l.) thylakoids against freeze-thaw damage is quantitatively related to their ability to reduce the solute loading of the vesicles during freezing. in the present paper we show that this effect is based on a reduction of the solute permeability of the membranes. permeability was measured with 14c-labeled glucose at temperatures between 0 and 10 degrees c. glucose permeability was reduced by both ... | 1994 | 8305457 |
| the effects of illumination on the xanthophyll composition of the photosystem ii light-harvesting complexes of spinach thylakoid membranes. | the xanthophyll composition of the light-harvesting chlorophyll a/b proteins of photosystem ii (lhcii) has been determined for spinach (spinacia oleracea l.) leaves after dark adaptation and following illumination under conditions optimized for conversion of violaxanthin into zeaxanthin. each of the four lhcii components was found to have a unique xanthophyll composition. the major carotenoid was lutein, comprising 60% of carotenoid in the bulk lhciib and 35 to 50% in the minor lhcii components ... | 1994 | 12232075 |
| a cdna encoding the endoplasmic reticulum-luminal heat-shock protein from spinach (spinacia oleracea l.). | | 1994 | 8115556 |
| embryogenesis and plant regeneration of spinach (spinacia oleracea l.) from hypocotyl segments. | a system for somatic embryogenesis and plant regeneration of spinach from hypocotyl segments has been established. callus was induced on solid media supplemented with 8.5-15.0 mg.l(-1) of indole-3-acetic acid and 3.46-34.64 mg.l(-1) gibberellic acid. callus was then subcultured on different media (solid or liquid) with or without iaa, or continuously maintained on the initiating media. somatic embryos were obtained in subcultures on iaa-containing media as well as in long-term cultures on initia ... | 1993 | 24196289 |
| the xanthophyll cycle, protein turnover, and the high light tolerance of sun-acclimated leaves. | changes in photosynthesis rate and photochemical characteristics in response to high irradiance, followed by recovery at low irradiance, were determined in four groups of sun-acclimated leaves of spinach (spinacia oleracea l.). these four groups were untreated control leaves, leaves treated with either an inhibitor of energy dissipation associated with the xanthophyll cycle (dithiothreitol, dtt) or an inhibitor of chloroplast-encoded protein synthesis (chloramphenicol, cap), as well as leaves tr ... | 1993 | 12232035 |
| choline synthesis in spinach in relation to salt stress. | choline metabolism was examined in spinach (spinacia oleracea l.) plants growing under nonsaline and saline conditions. in spinach, choline is required for phosphatidylcholine synthesis and as a precursor for the compatible osmolyte glycine betaine (betaine). when control (nonsalinized) leaf discs were incubated for up to 2 h with [1,2-14c]ethanolamine, label appeared in the n-methylated derivatives of phosphoethanolamine including phosphomono-, phosphodi-, and phosphotri- (i.e. phosphocholine) ... | 1993 | 12232019 |
| on the function of mitochondrial metabolism during photosynthesis in spinach (spinacia oleracea l.) leaves (partitioning between respiration and export of redox equivalents and precursors for nitrate assimilation products). | the functioning of isolated spinach (spinacia oleracea l.) leaf mitochondria has been studied in the presence of metabolite concentrations similar to those that occur in the cytosol in vivo. from measurements of the concentration dependence of the oxidation of the main substrates, glycine and malate, we have concluded that the state 3 oxidation rate of these substrates in vivo is less than half of the maximal rates due to substrate limitation. analogously, we conclude that under steady-state con ... | 1993 | 12232008 |
| in vitro bioavailability of iron from spinach (spinacea oleracea) cultivated in soil fortified with graded levels of iron and zinc. | a pot-culture experiment was conducted to assess the bioavailability of iron from spinach cultivated in soil fortified with graded levels of iron and zinc (feso4 x 7h2(0) and znso4 x 7h2(0), respectively). applications of varying levels of iron to soil increased the total iron and phosphorus contents and decreased the zinc content (p < 0.05). the effect of applying varying levels of zinc was the opposite of on the minerals in spinach. the ascorbic acid content was remarkably reduced with varying ... | 1993 | 8295863 |
| galactose-specific lectins protect isolated thylakoids against freeze-thaw damage. | we have measured freeze-thaw damage to isolated spinach (spinacia oleracea l.) chloroplast thylakoid membranes in the presence of different galactose-specific seed lectins to determine whether the binding of proteins to the membrane surface can lead to cryoprotection. of the seven lectins investigated, five were protective to different degrees and two showed no measurable effect. protection was afforded by a reduction of the solute permeability of the membranes. this reduced the solute influx du ... | 1993 | 12231914 |
| gibberellin a1 is required for stem elongation in spinach. | the effects of the growth retardants 2'-isopropyl-4'-(trimethylammonium chloride)-5'-methylphenyl piperidine-1-carboxylate (amo-1618) and calcium 3,5-dioxo-4-propionylcyclohexanecarboxylate (bx-112) on stem elongation were investigated in the rosette plant spinach (spinacia oleracea l.) under long-day (ld) conditions. stem growth induced by a ld treatment was prevented by both retardants. the inhibition caused by amo-1618 was reversed by gibberellin a1 (ga1) and ga20, whereas the effects of bx-1 ... | 1993 | 11607418 |
| effects of o2 and co2 on nonsteady-state photosynthesis (further evidence for ribulose-1,5-bisphosphate carboxylase/oxygenase limitation). | the effects of co2 and o2 on nonsteady-state photosynthesis following an increase in photosynthetic photon flux density (ppfd) were examined in spinacia oleracea to investigate the hypotheses that (a) a slow exponential phase (the ribulose-1,5-bisphosphate carboxylase/oxygenase [rubisco] phase) of nonsteady-state photosynthesis is primarily limited by rubisco activity and (b) rubisco activation involves two sequential, light-dependent processes as described in a previous study (i.e. woodrow, k.a ... | 1993 | 12231872 |
| identification of the main species of tetrapyrrolic pigments in envelope membranes from spinach chloroplasts. | the chlorophyll precursors protochlorophyllide and chlorophyllide were identified in purified envelope membranes from spinach (spinacia oleracea) chloroplasts. this was shown after pigment separation by high performance liquid chromatography (hplc) using specific fluorescence detection for these compounds. protochlorophyllide and chlorophyllide concentrations in envelope membranes were in the range of 0.1 to 1.5 nmol/mg protein. chlorophyll content of the envelope membranes was extremely low (0. ... | 1993 | 12231869 |
| respiration of sugars in spinach (spinacia oleracea), maize (zea mays), and chlamydomonas reinhardtii f-60 chloroplasts with emphasis on the hexose kinases. | the role of hexokinase in carbohydrate degradation in isolated, intact chloroplasts was evaluated. this was accomplished by monitoring the evolution of 14co2 from darkened spinach (spinacia oleracea), maize (zea mays) mesophyll, and chlamydomonas reinhardtii chloroplasts externally supplied with 14c-labeled fructose, glucose, mannose, galactose, maltose, and ribose. glucose and ribose were the preferred substrates with the chlamydomonas and maize chloroplasts, respectively. the rate of co2 relea ... | 1993 | 12231848 |
| aspects of subunit interactions in the chloroplast atp synthase (i. isolation of a chloroplast coupling factor 1-subunit iii complex from spinach thylakoids). | a chloroplast atp synthase complex (cf1 [chloroplast-coupling factor 1]-cf0 [membrane-spanning portion of chloroplast atp synthase]) depleted of all cf0 subunits except subunit iii (also known as the proteolipid subunit) was purified to study the interaction between cf1 and subunit iii. subunit iii has a putative role in proton translocation across the thylakoid membrane during photophosphorylation; therefore, an accurate model of subunit inter-actions involving subunit iii will be valuable for ... | 1993 | 12231815 |
| photoregulation of fructose and glucose respiration in the intact chloroplasts of chlamydomonas reinhardtii f-60 and spinach. | the photoregulation of chloroplastic respiration was studied by monitoring in darkness and in light the release of 14co2 from whole chloroplasts of chlamydomonas reinhardtii f-60 and spinach (spinacia oleracea l.) supplied externally with [14c] glucose and [14c]-fructose, respectively. co2 release was inhibited more than 90% in both chloroplasts by a light intensity of 4 w m-2. oxidants, oxaloacetate in chlamydomonas, nitrite in spinach, and phenazine methosulfate in both chloroplasts, reversed ... | 1993 | 12231784 |
| effects of anaerobiosis on chlorophyll fluorescence yield in spinach (spinacia oleracea) leaf discs. | when spinach (spinacia oleracea) leaf discs were incubated in a dark anaerobic environment, the chlorophyll fluorescence yield was much increased relative to the aerobic control. occasionally, the fluorescence yield of the darkened anaerobic samples approached 80% of the maximum fluorescence. the anaerobic incubation period also induced in a leaf disc the capacity to exhibit a low light-mediated chlorophyll fluorescence induction phenomenon. this involved a rapid and slow increase in fluorescenc ... | 1993 | 12231769 |
| response of a nitrite-reductase 3.1-kilobase upstream regulatory sequence from spinach to nitrate and light in transgenic tobacco. | in the present study the question was addressed of whether the nitrite-reductase (nir-)promoter from spinach (spinacia oleracea l.), fused to a reporter gene (bacterial β-glucuronidase, gus) and introduced into tobacco (nicotiana tabacum l.) responds to nitrate and light in accordance with spinach (donor) or in accordance with tobacco (host). the data obtained at the gus enzyme level as well as at the transcript level allow an unambiguous answer to this question: gus gene expression under the co ... | 1993 | 24178503 |
| photoinhibition of photosystem ii in vivo is preceded by down-regulation through light-induced acidification of the lumen: consequences for the mechanism of photoinhibition in vivo. | the mechanism of photoinhibition of photosystem ii (psii) was studied in intact leaf discs of spinacia oleracea l. and detached leaves of vigna unguiculata l. the leaf material was exposed to different photon flux densities (pfds) for 100 min, while non-photochemical (qn) and photochemical quenching (qp) of chlorophyll fluorescence were monitored. the 'energy' and redox state of psii were manipulated quite independently of the pfd by application of different temperatures (5-20° c), [co2] and [o2 ... | 1993 | 24178492 |
| role of ascorbate in detoxifying ozone in the apoplast of spinach (spinacia oleracea l.) leaves. | both reduced and oxidized ascorbate (aa and dha) are present in the aqueous phase of the extracellular space, the apoplast, of spinach (spinacia oleracea l.) leaves. fumigation with 0.3 [mu]l l-1 of ozone resulted in ozone uptake by the leaves close to 0.9 pmol cm-2 of leaf surface area s-1. apoplastic aa was slowly oxidized by ozone. the initial decrease of apoplastic aa was <0.1 pmol cm-2 s-1. the apoplastic ratio of aa to (aa + dha) decreased within 6 h of fumigation from 0.9 to 0.1. initiall ... | 1993 | 12231749 |
| 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 ... | 1993 | 8435075 |
| inhibition of thylakoid atpase by venturicidin as an indicator of cf1-cf0 interaction. | venturicidin inhibits the f0 portion of membrane-located, h+-pumping atpases. we find it meets the criteria for an energy transfer inhibitor for spinach (spinacia oleracea) thylakoids: complete inhibition of photophosphorylation and of photophosphorylation-stimulated and basal electron flow rates, but not of electron flow under uncoupled conditions. the extent of h+ uptake in the light is stimulated by venturicidin (vtcd), as expected for a compound blocking h+ efflux through cf0. vtcd had no ef ... | 1993 | 12231671 |
| cloning and developmental expression of the sucrose-phosphate-synthase gene from spinach. | a 561-base-pair (bp) polymerase-chain-reaction (pcr) product of sucrose-phosphate synthase (sps) was amplified using degenerate oligonucleotide primers corresponding to tryptic peptides of sps (ec 2.4.1.14) from spinach (spinacia oleracea l). crucial to the primer specificity and the synthesis of the 561-bp product was the use of primer pools in which the number of degenerate primer species was limited. a full-length cdna was subsequently obtained by screening a cdna bacteriophage library with t ... | 1993 | 7763823 |
| photosystem ii core phosphorylation heterogeneity, differential herbicide binding, and regulation of electron transfer in photosystem ii preparations from spinach. | the effect of photosystem ii core phosphorylation on the secondary quinone acceptor of photosystem ii (q(b)) domain environment was analyzed by comparative herbicide-binding studies with photosystem ii preparations from spinach (spinacia oleracea l.). it was found that phosphorylation reduces the binding affinity for most photosynthetic herbicides. the binding of synthetic quinones and of the electron acceptor 2,6-dichlorophenolindophenol is also reduced by photosystem ii phosphorylation. four p ... | 1992 | 16653222 |
| biochemical characterization of photosystem ii antenna polypeptides in grana and stroma membranes of spinach. | the photosystem (ps) ii antenna system comprises several biochemically and spectroscopically distinct complexes, including light-harvesting complex ii (lhcii), chlorophyll-protein complex (cp) 29, cp26, and cp24. lhcii, the most abundant of these, is both structurally and functionally diverse. the photosynthetic apparatus is laterally segregated within the thylakoid membrane into psi-rich and psii-rich domains, and the distribution of antenna complexes between these domains has implications for ... | 1992 | 16653152 |
| expression of the large atp synthase gene cluster in spinach plastids during light-induced development. | the large atp synthase gene cluster in spinach (spinacia oleracea) plastids encodes four of the six chloroplast-encoded atp synthase subunits. expression of this cluster was examined to determine its response to light-induced plastid development. spinach plastid transcripts were isolated from etiolated tissues, etiolated tissues exposed to 24 h of light, young (1-3 cm) leaves, and mature (8-10 cm) leaves. transcript levels were examined from each developmental stage as a function of either the q ... | 1992 | 16653100 |
| flow cytometry of spinach chloroplasts : determination of intactness and lectin-binding properties of the envelope and the thylakoid membranes. | intact spinach (spinacia oleracea) chloroplasts, thylakoid membranes, and inside-out or right-side-out thylakoid vesicles have been characterized by flow cytometry with respect to forward angle light scatter, right angle light scatter, and chlorophyll fluorescence. analysis of intact chloroplasts with respect to forward light scatter and the chlorophyll fluorescence parameter revealed the presence of truly "intact" and "disrupted" chloroplasts. the forward light scatter parameter, normally consi ... | 1992 | 16653090 |
| comparative studies of the light modulation of nitrate reductase and sucrose-phosphate synthase activities in spinach leaves. | we recently obtained evidence that the activity of spinach (spinacia oleracea l.) leaf nitrate reductase (nr) responds rapidly and reversibly to light/dark transitions by a mechanism that is strongly correlated with protein phosphorylation. phosphorylation of the nr protein appears to increase sensitivity to mg(2+) inhibition, without affecting activity in the absence of mg(2+). in the present study, we have compared the light/dark modulation of sucrose-phosphate synthase (sps), also known to be ... | 1992 | 16653049 |
| artifactual detection of adp-dependent sucrose synthase in crude plant extracts. | results presented in a previous report from this laboratory indicated the presence, in crude extracts from sycamore (acer pseudoplatanus) and spinach (spinacea oleracea), of a sucrose synthase (ec 2.4.1.13) showing high affinity for adp as the glucose acceptor in the sucrose-cleaving reaction. in the present paper we report that the modified enzymatic method previously used to measure sucrose synthase activities leads to the detection of artifactual adp-dependent sucrose synthase, which in fact ... | 1992 | 1387619 |
| hydration-state-responsive proteins link cold and drought stress in spinach. | spinach (spinacia oleracea l.) seedlings exposed to low nonfreezing temperatures (0-10° c) that promote cold acclimation, synthesize a variety cold-acclimation proteins and at the same time acquire a greater ability to withstand cellular dehydration imposed by the freezing of tissue water. two of these proteins (160 and 85 kda) become more abundant over time at low temperature. in addition, a small decline in tissue water status from a maximally hydrated state also appears to be associated with ... | 1992 | 24178264 |
| sucrose phosphate synthase and sucrose accumulation at low temperature. | the influence of growth temperature on the free sugar and sucrose phosphate synthase content and activity of spinach (spinacia oleracea) leaf tissue was studied. when plants were grown at 25 degrees c for 3 weeks and then transferred to a constant 5 degrees c, sucrose, glucose, and fructose accumulated to high levels during a 14-d period. predawn sugar levels increased from 14- to 20-fold over the levels present at the outset of the low-temperature treatment. sucrose was the most abundant free s ... | 1992 | 16652990 |
| characterization of an electron transport pathway associated with glucose and fructose respiration in the intact chloroplasts of chlamydomonas reinhardtii and spinach. | the role of an electron transport pathway associated with aerobic carbohydrate degradation in isolated, intact chloroplasts was evaluated. this was accomplished by monitoring the evolution of (14)co(2) from darkened spinach (spinacia oleracea) and chlamydomonas reinhardtii chloroplasts externally supplied with [(14)c]fructose and [(14)c]glucose, respectively, in the presence of nitrite, oxaloacetate, and conventional electron transport inhibitors. addition of nitrite or oxaloacetate increased th ... | 1992 | 16652964 |
| effects of the air pollutant so(2) on leaves : inhibition of sulfite oxidation in the apoplast by ascorbate and of apoplastic peroxidase by sulfite. | after so(2) has entered leaves of spinach (spinacia oleracea) through open stomata and been hydrated in the aqueous phase of cell walls, the sulfite formed can be oxidized to sulfate by an apoplastic peroxidase that is normally involved in phenol oxidation. the oxidation of sulfite is competitive with the oxidation of phenolics. during sulfite oxidation, the peroxidase is inhibited. in the absence of ascorbate, which is a normal constituent of the aqueous phase of the apoplast, peroxidative sulf ... | 1992 | 16652957 |
| lithium decreases cold-induced microtubule depolymerization in mesophyll cells of spinach. | freezing, dehydration, and supercooling cause microtubules in mesophyll cells of spinach (spinacia oleracea l. cv bloomsdale) to depolymerize (me bartolo, jv carter [1991] plant physiol 97: 175-181). the objective of this study was to gain insight into the question of whether microtubules depolymerize as a direct response to environmental stresses or as an indirect response to cellular changes that accompany the stresses. leaf sections of spinach were treated with li(+) before and during exposur ... | 1992 | 16669100 |
| identification of factors regulating the phosphorylation status of sucrose-phosphate synthase in vivo. | the purpose of this study was to identify the factors that control sucrose-phosphate synthase (sps)-kinase and sps-protein phosphatase (sps-pp) activity in situ, and thereby mediate the activation of sps by light or mannose. feeding mannose to excised spinach (spinacia oleracea) leaves in darkness resulted in a general sequestration of cellular phosphate (as evidenced by accumulation of mannose-6-p and depletion of glucose-6-p [glc-6-p] and fructose-6-p [fru-6-p]) and a relatively slow activatio ... | 1992 | 16669055 |
| regulation of plastid gene expression during photooxidative stress. | we have used the carotenoid biosynthesis inhibitor norflurazon to study the relationship between chloroplast and nuclear gene expression and the mechanisms by which plastid mrna accumulation is regulated in response to photooxidative stress. by treating 4-week-old hydroponic spinach plants (spinacea oleracea), we were able to determine the response at two distinct stages of chloroplast development. for all parameters studied, differences were found between the norflurazon-treated young and matur ... | 1992 | 16669052 |
| association of 70-kilodalton heat-shock cognate proteins with acclimation to cold. | exposure of young spinach seedlings (spinacia oleracea l. cv bloomsdale) to 5 degrees c leads to an increase in the synthesis of several 79-kilodalton proteins that are present in leaf tissue grown at 20 degrees c. protein sequence analyses and immunological cross-reactivity indicate that this group of proteins belongs to the 70-kilodalton heat-shock family. steady-state transcript levels and protein synthesis are increased two- to threefold within 1 day, but immunoblot analyses suggest that the ... | 1992 | 16669045 |
| dissociation of ribulose-1,5-bisphosphate bound to ribulose-1,5-bisphosphate carboxylase/oxygenase and its enhancement by ribulose-1,5-bisphosphate carboxylase/oxygenase activase-mediated hydrolysis of atp. | ribulose bisphosphate (rubp), a substrate of ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), is an inhibitor of rubisco activation by carbamylation if bound to the inactive, noncarbamylated form of the enzyme. the effect of rubisco activase on the dissociation kinetics of rubp bound to this form of the enzyme was examined and characterized with the use of (3)h-labeled rubp and proteins purified from spinach (spinacia oleracea l.) in the absence of rubisco activase and in the presence ... | 1992 | 16669043 |
| organization and topology of photosystem i subunits. | intact spinach (spinacia oleracea) thylakoid membranes were treated with various proteases and photosystem i (psi) complexes were isolated from these membranes to define the membrane topology of specific psi subunits. trypsin treatment caused cleavage of the psi-d and e subunits. thermolysin treatment cleaved the psi-d, e, h, and k subunits, and also caused limited degradation of the reaction center core psi-a and b subunits. pronase treatment produced the most dramatic results as the psi-a and ... | 1992 | 16669018 |
| alteration of spinach ribulose-1,5-bisphosphate carboxylase/oxygenase activase activities by site-directed mutagenesis. | site-directed mutagenesis was performed on the 1.6 and 1.9 kilobase spinach (spinacea oleracea) ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) activase cdnas, encoding the 41 and 45 kilodalton (kd) isoforms of the enzyme, to create single amino acid changes in the putative atp-binding site of rubisco activase (lys-107, gln-109, and ser-112) and in an unrelated cysteine residue (cys-256). replacement of lys-107 with met produced soluble protein with reduced rubisco activase and atpase ... | 1992 | 16668989 |
| developmental history affects the susceptibility of spinach leaves to in vivo low temperature photoinhibition. | room temperature chlorophyll a fluorescence was used to determine the effects of developmental history, developmental stage, and leaf age on susceptibility of spinach to in vivo low temperature (5 degrees c) induced photoinhibition. spinach (spinacia oleracea cv savoy) leaves expanded at cold hardening temperatures (5 degrees c day/night), an irradiance of 250 micromoles per square meter per second of photosynthetic proton flux density, and a photoperiod of 16 hours were less sensitive than leav ... | 1992 | 16668980 |
| nucleotide sequence of a cdna clone encoding a precursor to stearoyl-(acyl-carrier-protein) desaturase from spinach, spinacia oleracea. | | 1992 | 1627785 |
| reversible light/dark modulation of spinach leaf nitrate reductase activity involves protein phosphorylation. | spinach (spinacia oleracea l.) leaf nitrate reductase (nadh:nr;nadh:nitrate oxidoreductase, ec 1.6.6.1) activity was found to rapidly change during light/dark transitions. the most rapid and dramatic changes were found in a form of nr which was sensitive to inhibition by millimolar concentrations of magnesium. this form of nr predominated in leaves in the dark, but was almost completely absent from leaves incubated in the light for only 30 min. when the leaves were returned to darkness, the nr r ... | 1992 | 1605645 |
| k stimulation of atpase activity associated with the chloroplast inner envelope. | studies were conducted to characterize atpase activity associated with purified chloroplast inner envelope preparations from spinach (spinacea oleracea l.) plants. comparison of free mg(2+) and mg.atp complex effects on atpase activity revealed that any mg(2+) stimulation of activity was likely a function of the use of the mg.atp complex as a substrate by the enzyme; free mg(2+) may be inhibitory. in contrast, a marked (one- to twofold) stimulation of atpase activity was noted in the presence of ... | 1992 | 16668922 |
| light-dependent changes in ribulose bisphosphate carboxylase activase activity in leaves. | an assay for the activity of ribulose bisphosphate carboxylase (rubisco) activase in crude leaf extracts was developed. the assay is based on a spectrophotometric assay of rubisco, and activase activity (in nanomoles activated rubisco per minute per milligram chlorophyll) was calculated from the rate of increase in rubisco activity over time. activase activity measurements were made using samples from spinach (spinacia oleracea) leaves undergoing (a) steady-state photosynthesis at various photon ... | 1992 | 16668866 |
| biphasic activation of ribulose bisphosphate carboxylase in spinach leaves as determined from nonsteady-state co(2) exchange. | the activation kinetics of ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) following an increase in photon flux density (pfd) were studied by analyzing co(2) assimilation time courses in spinach leaves (spinacia oleracea). when leaves were exposed to 45 minutes of darkness before illumination at 690 micromoles per square meter per second, rubisco activation followed apparent first-order kinetics with a relaxation time of about 3.8 minutes. but when leaves were illuminated for 45 minute ... | 1992 | 16668865 |
| site-specific serine phosphorylation of spinach leaf sucrose-phosphate synthase. | we recently reported [huber, huber & nielsen (1989) arch. biochem. biophys. 270, 681-690] that spinach (spinacia oleracea l.) sucrose-phosphate synthase (sps; ec 2.4.1.14) was phosphorylated in vivo when leaves were fed [32p]pi. in vitro the enzyme was phosphorylated and inactivated by using [gamma-32p]atp. we now report that sps is phosphorylated both in vivo and in vitro on serine residues. the protein is phosphorylated at multiple sites both in vivo and in vitro as indicated by two-dimensiona ... | 1992 | 1534222 |
| shoot regeneration from spinach hypocotyl segments by short term treatment with 5,6-dichloro-indole-3-acetic acid. | factors affecting shoot regeneration from hypocotyl segments of spinach (spinacia oleracea l.) were investigated. when expiants were cultured on medium containing 10 mg/l iaa for 7 weeks, 3 out of 9 cultivars showed relatively high shoot regeneration response (15 - 35%). the other pgrs tested had no effect on shoot regeneration. however, the transfer of explants from auxin-containing medium to auxin-free medium 20 d after culture induced shoot formation from expiants cultured on media containing ... | 1992 | 24213485 |