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ABSTRACT: The main purpose of this study was to explore the sites and mechanisms of action of metabotropic glutamate receptor 1 (mGluR1) blockade for antipsychotic-like activity using a Fos mapping approach, with the intent of better understanding the similarities and differences between the pharmacological actions of mGluR1 antagonists and atypical antipsychotic drugs such as clozapine. Previously, we showed that an allosteric mGluR1 antagonist (negative allosteric modulator), 2-cyclopropyl-5-[1-(2-fluoro-3-pyridinyl)-5-methyl-1H-1,2,3-triazol-4-yl]-2,3-dihydro-1H-isoindol-1-one (CFMTI), induces Fos expression in the nucleus accumbens and the medial prefrontal cortex (mPFC), but not in the dorsolateral striatum, similar to the action of clozapine. In the present study, the Fos expression profile of CFMTI was more extensively evaluated in various areas of the brain. CFMTI induced Fos expression mainly in glutamatergic neurons in the mPFC, in a manner similar to clozapine. A significant increase in Fos expression was also observed in the locous coeruleus, central amygdaloid nucleus, the bed nucleus of the stria terminalis and the primary somatosensory cortex, but not in the ventral tegmental area, dorsal raphe or lateral septum. Fos expression in orexin neurons in the lateral hypothalamic/perifornical area (LH/PFA) is known to be positively correlated with the weight gain liability of atypical antipsychotics. CFMTI did not increase Fos expression in orexin neurons in the LH/PFA, in contrast to clozapine, which does have weight gain liability. These results suggest that CFMTI has unique and shared actions on Fos expression in various regions of the brain compared with clozapine.
Neuroscience 07/2010; 168(3):787-96. · 3.38 Impact Factor
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ABSTRACT: It is widely believed that ferrochelatase (protoheme ferrolyase, EC 4.99.1.1), which catalyzes the insertion of ferrous ion into protoporphyrin IX to form protoheme, exists in both plastids and mitochondria of higher plants. By in vitro import assay with isolated pea (Pisum sativum L.) organelles, it has been proposed that one of two isoforms of ferrochelatase (type 1) is dual-targeted into both plastids and mitochondria, and functions for heme biosynthesis in the both organelles. Recently, however, mitochondrial targeting of ferrochelatase is being disputed since pea mitochondria appeared to accept a variety of chloroplast proteins including the type-1 ferrochelatase of Arabidopsis thaliana (L.) Heynh. To clarify the precise subcellular localization of ferrochelatase in higher plants, here we investigated the subcellular localization of two types of ferrochelatase (CsFeC1 and CsFeC2) in cucumber (Cucumis sativus L.). In cotyledons, a significant level of specific ferrochelatase activity was detected in thylakoid membranes, but only a trace level of activity was detectable in mitochondria. Western blot analysis with specific antibodies showed that anti-CsFeC2 antiserum cross-reacted with plastids in photosynthetic and non-photosynthetic tissues. Anti-CsFeC1 did not cross-react with mitochondria, but CsFeC1 was clearly detectable in plastids from non-photosynthetic tissues. In situ transient-expression assays using green fluorescent protein demonstrated that, as well as CsFeC2, the N-terminal transit peptide of CsFeC1 targeted the fusion protein solely into plastids, but not into mitochondria. These results demonstrated that in cucumber both CsFeC1 and CsFeC2 are solely targeted into plastids, but not into mitochondria. Screening of a cucumber genomic or cDNA library did not allow any other ferrochelatase homologous gene to be isolated. The data presented here imply the reconsideration of mitochondrial heme biosynthesis in higher plants.
Planta 09/2003; 217(4):602-9. · 3.00 Impact Factor
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ABSTRACT: In Arabidopsis, monogalactosyldiacylglycerol (MGDG) is synthesized by a multigenic family of MGDG synthases consisting of two types of enzymes differing in their N-terminal portion: type A (atMGD1) and type B (atMGD2 and atMGD3). The present paper compares type B isoforms with the enzymes of type A that are known to sit in the inner membrane of plastid envelope. The occurrence of types A and B in 16:3 and 18:3 plants shows that both types are not specialized isoforms for the prokaryotic and eukaryotic glycerolipid biosynthetic pathways. Type A atMGD1 gene is abundantly expressed in green tissues and along plant development and encodes the most active enzyme. Its mature polypeptide is immunodetected in the envelope of chloroplasts from Arabidopsis leaves after cleavage of its transit peptide. atMGD1 is therefore likely devoted to the massive production of MGDG required to expand the inner envelope membrane and build up the thylakoids network. Transient expression of green fluorescent protein fusions in Arabidopsis leaves and in vitro import experiments show that type B precursors are targeted to plastids, owing to a different mechanism. Noncanonical addressing peptides, whose processing could not be assessed, are involved in the targeting of type B precursors, possibly to the outer envelope membrane where they might contribute to membrane expansion. Expression of type B enzymes was higher in nongreen tissues, i.e., in inflorescence (atMGD2) and roots (atMGD3), where they conceivably influence the eukaryotic structure prominence in MGDG. In addition, their expression of type B enzymes is enhanced under phosphate deprivation.
Proceedings of the National Academy of Sciences 10/2001; 98(19):10960-5. · 9.68 Impact Factor
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ABSTRACT: Two distinct cDNA clones (IPI1 and IPI2) encoding IPI were isolated from Nicotiana tabacum. In situ expression of isopentenyl diphosphate isomerase-1 (IPI1)- and IPI2-green fluorescent protein fusion constructs revealed that IPI1 and IPI2 were localized in chloroplast and cytosol, respectively. The level of IPI1 mRNA was increased under high-salt and high-light stress conditions, while that of IPI2 mRNA was increased under high-salt and cold stress conditions. Both IPI transcripts were increased in an abscisic acid-independent manner. This is the first report of a cytosolic IPI. The results indicated that two distinct IPIs were differentially induced in response to stress.
FEBS Letters 10/2001; 506(1):61-4. · 3.54 Impact Factor
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ABSTRACT: Monogalactosyldiacylglycerol (MGDG) is a major constituent of thylakoid membrane in chloroplasts. Therefore, it is considered to have an important role in the maintenance of the complicated structure of the thylakoid membrane. We have succeeded in cloning the enzyme for MGDG synthesis and overexpressed it in Escherichia coli. In this study we analyzed the morphology of the E. coli harboring the gene. The fatty acid composition of its membrane lipids did not differ between the wild type and transformant, except for the appearance of MGDG. However, transformant cells appeared to be elongated. DAPI staining revealed the entire intracellular region of filamentous cells to be stained; therefore, the elongation of the cells is probably due to a defect in cell division. Atomic force microscopy revealed that the transformant had a smooth but scratched surface. It was concluded that the excessive accumulation of a non-bilayer lipid, MGDG, interfered with the translocation of proteins across the plasma membrane, including those for cell division.
Biochemical and Biophysical Research Communications 09/2001; 286(1):114-8. · 2.48 Impact Factor
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Y Sasaki,
E Asamizu,
D Shibata,
Y Nakamura,
T Kaneko,
K Awai,
M Amagai,
C Kuwata,
T Tsugane,
T Masuda,
H Shimada,
K Takamiya, H Ohta,
S Tabata
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ABSTRACT: Jasmonates mediate various physiological events in plant cells such as defense responses, flowering, and senescence through intracellular and intercellular signaling pathways, and the expression of a large number of genes appears to be regulated by jasmonates. In order to obtain information on the regulatory network of jasmonate-responsive genes (JRGs) in Arabidopsis thaliana (Arabidopsis), we screened 2880 cDNA clones for jasmonate responsiveness by a cDNA macroarray procedure. Since many of the JRGs reported so far have been identified in leaf tissues, the cDNA clones used were chosen from a non-redundant EST library that was prepared from above-ground organs. Hybridization to the filters was achieved using alpha-33P-labeled single-strand DNAs synthesized from mRNAs obtained from methyl jasmonate (MeJA)-treated and untreated Arabidopsis seedlings. Data analysis identified 41 JRGs whose mRNA levels were changed by more than three fold in response to MeJA. This was confirmed by Northern blot analysis by using eight representatives. Among the 41 JRGs identified, 5 genes were JA biosynthesis genes and 3 genes were involved in other signaling pathways (ethylene, auxin, and salicylic acid). These results suggest the existence of a positive feedback regulatory system for JA biosynthesis and the possibility of crosstalk between JA signaling and other signaling pathways.
DNA Research 09/2001; 8(4):153-61. · 5.16 Impact Factor
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ABSTRACT: The maize cysteine protease complex, which required SDS for its activation in vitro, is a 179 kDa trimeric complex (P-I)3 of a cysteine protease (P) [EC 3.4.22] and a cysteine protease inhibitor (I), cystatin [Yamada et al. (1998) Plant Cell Physiol. 39: 106, Yamada et al. (2000) Plant Cell Physiol. 41: 185]. Here, we show the mechanism of the SDS-dependent activation of the trimeric (P-I) complex and stabilization of the activated protease by its specific substrates. The cystatin-free cysteine protease isolated by preparative SDS-PAGE was still specifically activated by SDS, and its profile of SDS-dependency was exactly the same as that of the trimeric (P-I) complex. It is, therefore, evident that an SDS-dependent conformational change of the protease itself, rather than the release of cystatin from the complex, is crucial for the activation. Pre-treatment analysis with SDS revealed that SDS was required for the initiation of the activation of the trimeric (P-I) complex. Furthermore, we found that once the protease was activated, if there was no substrate, it was rapidly inactivated under optimum conditions of proteolysis, and showed that such inactivation was not due to autolysis of the protease. In contrast, addition of specific substrates prevented the inactivation, and thus we presumed that the activity of the cysteine protease is regulated by both activation by conformational change and rapid inactivation after consumption of substrates.
Plant and Cell Physiology 08/2001; 42(7):710-6. · 4.70 Impact Factor
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ABSTRACT: Monogalactosyldiacylglycerol (MGDG) synthase catalyses formation of MGDG, a major structural lipid of chloroplasts. We have already cloned a cDNA for the synthase from a cucumber cDNA library and shown that expression of this gene is regulated by light and a phytohormone, cytokinin. In the present study, we report the molecular basis for transcriptional regulation by light and cytokinin in detail. First, in terms of the enzyme activity, gradual increases in activity mediated by light and cytokinin treatments were observed. At the same time, however, the changes in the mRNA level showed different profiles, with a transient peak during the early stages of light and cytokinin treatment. The interval between the peak level of mRNA and enzyme activation implies the existence of a post-transcriptional regulatory system. In addition, a genomic clone of MGDG synthase isolated from a cucumber genome library was used for a motif search in databases, and this revealed that putative cis-acting elements for light and phytohormones exist in the 5'-upstream region of the MGD cucumber gene. Detailed analysis of this region for light- and cytokinin-responsive activity was performed using a -90 truncated 35 S minimal promoter/luciferase (LUC) reporter gene. It resulted in high levels of LUC expression in etiolated cucumber cotyledons in response to illumination and cytokinin treatment. These results indicate that this 5'-upstream region is involved in light- and cytokinin-enhanced MGD gene expression, and that light- and cytokinin-responsive enhancements of the MGDG synthase activity are regulated, at least in part, at the level of transcription.
Biochemical Society Transactions 01/2001; 28(6):738-40. · 3.71 Impact Factor
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Y Sasaki,
E Asamizu,
D Shibata,
Y Nakamura,
T Kaneko,
K Awai,
T Masuda,
H Shimada,
K Takamiya,
S Tabata, H Ohta
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ABSTRACT: Jasmonates are generally considered to mediate signalling, such as defence responses, flowering and senescence. However, factors involved in the jasmonate signal-transduction pathway remain unclear. To clarify the functions and signalling mechanisms of jasmonates on a genome-wide level, we adopted a cDNA macroarray technique. We prepared nylon filters of a cDNA macroarray on which 2880 independent expressed sequence tag clones of Arabidopsis were blotted, and hybridized (33)P-labelled single-strand DNAs synthesized from mRNAs of methyl jasmonate (MeJA)-treated and untreated Arabidopsis plants to the nylon filters. By analysing the data from the cDNA macroarray, we identified many function-known and unknown genes as MeJA-responsive genes, and confirmed that the profiles of the expression showed good agreement with Northern-blot analysis. These results demonstrate the efficiency of the cDNA macroarray for systematically analysing jasmonate-responsive genes on a genome-wide scale.
Biochemical Society Transactions 01/2001; 28(6):863-4. · 3.71 Impact Factor
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ABSTRACT: Because the synthesis of monogalactosyldiacylglycerol (MGDG) is unique to plants, identified as an important marker of the plastid envelope, involved in a key step of plastid biogenesis and is the most abundant lipid on earth, MGDG synthase activity was extensively analysed at the biochemical and physiological levels. In the present paper, we present our current knowledge on the MGDG synthase's function, structure and topology in envelope membranes, and discuss possible roles in plant cell glycerolipid metabolism. The recent discovery of a multigenic family of MGDG synthases raised the possibility that multiple isoenzymes might carry out MGDG synthesis in various tissues and developmental stages.
Biochemical Society Transactions 01/2001; 28(6):732-8. · 3.71 Impact Factor
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ABSTRACT: In Arabidopsis thaliana, we identified a novel gene of a NADPH-protochlorophyllide oxidoreductase (POR) isoform, which catalyzes the light-dependent protochlorophyllide a reduction in the chlorophyll (Chl) biosynthetic pathway. The deduced amino acid sequence of the novel POR isoform (PORC) showed significant identities ( approximately 75%) with the previously isolated two POR isoforms of A. thaliana. Contrasting with these POR isoforms, the PORC transcript increased in etiolated seedlings by illumination, and was dominantly expressed in immature and mature tissues. The present results demonstrated that Chl biosynthesis and chloroplast biogenesis in A. thaliana are controlled by three POR isoforms, which are differentially controlled by light and development.
FEBS Letters 07/2000; 474(2-3):133-6. · 3.54 Impact Factor
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ABSTRACT: Photoreduction of protochlorophyllide a to chlorophyllide a that is catalyzed by NADPH-protochlorophyllide oxidoreductase (NPR) is only a light-dependent step in overall processes of biosynthesis of Chl in angiosperms. Unlike many other plants, in fully green leaves of cucumber the expression of only a single NPR gene of cucumber was positively regulated by light and developmental age of leaf, and also by diurnal and circadian rhythms. The single NPR gene was shown to be involved in Chl synthesis throughout of the vegetative growth of cucumber (in cotyledons and fully green leaves).
Plant and Cell Physiology 03/2000; 41(2):226-9. · 4.70 Impact Factor
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ABSTRACT: Ferrochelatase catalyzes the insertion of Fe2+ into protoporphyrin IX to generate protoheme. A putative mature region of a cucumber ferrochelatase cDNA (hemH) was overexpressed in Escherichia coli and purified to homogeneity (40 kDa). The optimum pH was 7.7, and the apparent K(m) values for deuteroporphyrin IX and Fe2+ were 14.4 microM and 4.7 microM, respectively. The activity of the ferrochelatase was inhibited by N-methylprotoporphyrin IX (I50 = 4 nM). Western blot analysis with a polyclonal antibody raised against the recombinant ferrochelatase showed that the antibody crossreacted with protein extracts from hypocotyls and roots of cucumber but not with that from cotyledons. The antibody did not crossreact with proteins of thylakoid membranes of chloroplasts in cucumber cotyledons, although the ferrochelatase activity was mainly associated with the thylakoid membranes. Northern blot analysis also indicated that the hemH gene was expressed mainly in hypocotyls and roots, but little in cotyledons, and the level of the hemH transcripts was not light-responsive. These results demonstrated that the cucumber hemH gene encodes a ferrochelatase which presumably functions for heme biosynthesis in non-photosynthetic tissues, such as hypocotyls and roots, and suggested the presence of other types of ferrochelatase in cucumber, one of which is located in thylakoid membranes of chloroplasts.
Plant and Cell Physiology 03/2000; 41(2):192-9. · 4.70 Impact Factor
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ABSTRACT: We recently purified a latent but SDS-activated protease complex (40, 15- or 13-kDa proteins) from maize [Yamada et al. (1998) Plant Cell Physiol. 39: 106]. Here, we revealed that the complex was composed of a cysteine protease (40 kDa) and a cystatin, cysteine protease inhibitor (15- or 13-kDa). This is the first report on the isolation of a complex consisting of a cystatin and a target cysteine protease from plants. Cloning of the cysteine protease revealed that it had low homology (25-30%) to other maize cysteine proteases cloned to date but was highly homologous to other plant cysteine proteases such as rice oryzain alpha (84%) and the homologs (50-80%). The cysteine protease expressed in Escherichia coli showed the same substrate and inhibitor specificities as the protease of the complex, demonstrating that the isolated cDNA clone exactly encodes the protease of the complex. The protease expressed in E. coli itself was active but not latent, probably because it was not bound to cystatin. It is most likely that in vitro activation of the protease complex by SDS is caused by the release of bound cystatin. The mRNA of protease was expressed in various tissues except for seeds.
Plant and Cell Physiology 03/2000; 41(2):185-91. · 4.70 Impact Factor
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ABSTRACT: NADPH-protochlorophyllide oxidoreductase (POR) catalyzes the photoreduction of protochlorophyllide a in the chlorophyll biosynthetic pathway. Recently, two POR genes, the expressions of which were differently regulated by light, were isolated in barley and Arabidopsis, and it is suggested that in angiosperms, the chlorophyll synthesis is controlled by the differential action of the two distinct POR isozymes. Meanwhile, we have isolated POR cDNA from cucumber, and reported that its expression was enhanced by illumination. In this study, we analyzed the gene expression and organization of cucumber POR in more detail. Northern blot analysis with 5'- or 3'-noncoding gene-specific and full length probes and RNase protection assay revealed that cucumber POR mRNA is transcribed from a single gene. Run-on assay revealed that the transcript level of isolated nuclei from illuminated cotyledons was 6-fold that of dark control, indicating that the light-enhanced expression of cucumber POR is caused by transcriptional activation. Using degenerated primers and the genomic DNA of cucumber as template, PCR showed the presence of only one type of fragment encoding cucumber POR. The PCR product was hybridized with the genomic Southern blot from cucumber and only one band was detected under low stringency conditions. From these results, we conclude that there is a single POR gene in cucumber and PORs are organized by different gene families among higher plants, and in cucumber the single POR may play the roles of two POR genes, which are present in other higher plants such as Arabidopsis and barley.
Photosynthesis Research 02/2000; 64(2-3):147-54. · 3.24 Impact Factor
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ABSTRACT: Chlorophyllase (Chlase) is the first enzyme involved in chlorophyll (Chl) degradation and catalyzes the hydrolysis of ester bond to yield chlorophyllide and phytol. In the present study, we isolated the Chlase cDNA. We synthesized degenerate oligo DNA probes based on the internal amino acid sequences of purified Chlase from Chenopodium album, screened the C. album cDNA library, and cloned a cDNA (CaCLH, C. album chlorophyll-chlorophyllido hydrolase). The deduced amino acid sequence (347 aa residues) had a lipase motif overlapping with an ATP/GTP-binding motif (P-loop). CaCLH possibly was localized in the extraplastidic part of the cell, because a putative signal sequence for endoplasmic reticulum is at the N terminus. The amino acid sequence shared 37% identity with a function-unknown gene whose mRNA is inducible by coronatine and methyl jasmonate (MeJA) in Arabidopsis thaliana (AtCLH1). We expressed the gene products of AtCLH1 and of CaCLH in Escherichia coli, and they similarly exhibited Chlase activity. Moreover, we isolated another full-length cDNA based on an Arabidopsis genomic fragment and expressed it in E. coli, demonstrating the presence of the second Arabidopsis CLH gene (AtCLH2). No typical feature of signal sequence was identified in AtCLH1, whereas AtCLH2 had a typical signal sequence for chloroplast. AtCLH1 mRNA was induced rapidly by a treatment of MeJA, which is known to promote senescence and Chl degradation in plants, and a high mRNA level was maintained up to 9 h. AtCLH2, however, did not respond to MeJA.
Proceedings of the National Academy of Sciences 12/1999; 96(26):15362-7. · 9.68 Impact Factor
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ABSTRACT: To elucidate the mechanism for formation of zinc-containing bacteriochlorophyll a in the photosynthetic bacterium Acidiphilium rubrum, we isolated homologs of magnesium chelatase subunits (bchI, -D, and -H). A. rubrum bchI and -H were encoded by single genes located on the clusters bchP-orf168-bchI-bchD-orf320-crtI and bchF-N-B-H-L as in Rhodobacter capsulatus, respectively. The deduced sequences of A. rubrum bchI, -D, and -H had overall identities of 59. 8, 40.5, and 50.7% to those from Rba. capsulatus, respectively. When these genes were introduced into bchI, bchD, and bchH mutants of Rba. capsulatus for functional complementation, all mutants were complemented with concomitant synthesis of bacteriochlorophyll a. Analyses of bacteriochlorophyll intermediates showed that A. rubrum cells accumulate magnesium protoporphyrin IX monomethyl ester without detectable accumulation of zinc protoporphyrin IX or its monomethyl ester. These results indicate that a single set of magnesium chelatase homologs in A. rubrum catalyzes the insertion of only Mg(2+) into protoporphyrin IX to yield magnesium protoporphyrin IX monomethyl ester. Consequently, it is most likely that zinc-containing bacteriochlorophyll a is formed by a substitution of Zn(2+) for Mg(2+) at a step in the bacteriochlorophyll biosynthesis after formation of magnesium protoporphyrin IX monomethyl ester.
Journal of Biological Chemistry 12/1999; 274(47):33594-600. · 4.77 Impact Factor
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ABSTRACT: MGDG synthase, the enzyme that catalyzes the synthesis of the major chloroplast membrane lipid monogalactosyldiacylglycerol (MGDG), is encoded by a multigenic family. We have analyzed the biochemical properties, subcellular localization and membrane topology of a spinach chloroplast MGDG synthase, a representative member of the type A family from Spinacia oleracea (soMGD A), using a recombinant protein that was functionally overexpressed in Escherichia coli and specific polyclonal antibodies. We demonstrated that soMGD A could catalyze the synthesis of both 'prokaryotic' and 'eukaryotic' MGDG molecular species in vitro, with a selectivity for diacylglycerol similar to that of purified chloroplast envelope MGDG synthase activity. Furthermore, soMGD A was shown to be sensitive to chemical reagents (dithiothreitol, N-ethylmaleimide and o-phenanthroline) known to affect MGDG synthesis by the partially purified enzyme, as well as in isolated chloroplast envelope membranes. In spinach chloroplasts, soMGD A was localized by Western blot analysis in the inner envelope membrane. Topological studies demonstrated that soMGD A is a monotopic enzyme, embedded within one leaflet of the inner envelope membrane from spinach chloroplasts, a structure which may involve amphipathic alpha helices. We further demonstrated that in vitro, soMGD A precursor is imported and processed to its correct mature form in intact chloroplasts. These results show that soMGD A corresponds to a mature polypeptide of approximately 45 kDa. In addition, inactivation kinetics after gamma-ray irradiation strongly suggest that both native chloroplast envelope MGDG synthase and recombinant soMGD A have a functional molecular mass of 95-100 kDa, indicating that they are probably active as homodimers made of two 45-kDa subunits. This study suggests that, in spite of the growing evidence that MGDG synthesis is catalyzed by a multigenic family of enzymes, in spinach leaves both prokaryotic and eukaryotic MGDG syntheses could be attributable to a unique dimeric enzyme, provided that diacylglycerol is transported from the outer membrane to the inner membrane of the chloroplast envelope.
European Journal of Biochemistry 12/1999; 265(3):990-1001. · 3.58 Impact Factor
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ABSTRACT: We previously cloned a trans-repressor, SPB, for the puf operon of Rhodobacter sphaeroides (Shimada et al. 1996) and revealed that SPB was a putative genetic counterpart to HvrA in Rhodobacter capsulatus, a trans-activator for the puf and puh operons (Mizoguchi et al. 1997). In this study we constructed a spb-disrupted R. sphaeroides, strain L-7, to elucidate the function of SPB. This disruption of the spb gene increased the photosynthetic growth rate and the cellular levels of photopigments under low-intensity light conditions. The disruption also derepressed the expression of the puf and puc operons under high-intensity light conditions. In strain L-7, however, strong illumination still reduced the cellular levels of photopigments as it did in the wild strain, suggesting that SPB did not directly affect the formation of photopigments. These results support our previous suggestion that SPB functions as a high-light repressor for puf operon in R. sphaeroides in striking contrast to HvrA, which is a low-light activator for puf and puh operons in R. capsulatus, even though SPB and HvrA are highly homologous. Disruption of spb gene had no effect on the oxygen-mediated regulation of the pigmentation or the expression of puf and puc operons.
Plant and Cell Physiology 05/1998; 39(4):411-7. · 4.70 Impact Factor
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ABSTRACT: From the soybean cDNA library, we isolated and analyzed the chlH gene encoding a subunit of Mg-chelatase. The subunit was a polypeptide of 1,383 amino acids with a molecular mass of 153,491 Da, which shared 90% identity with the olive gene from Antirrhinum majus. The regulation of the expression of chlH was investigated in photomix-otrophic soybean suspension cells (SB-P). The expression was light-inducible, and the induction was more rapid than those of chlI and cab2. Furthermore, the levels of the transcripts and products of chlH appeared to be regulated by a circadian oscillation. The subchloroplastic localization of ChlH was investigated by immunoblot analyses with antiserum against recombinant ChlH. Depending on the concentration of Mg2+ in the lysis buffer, the localization of ChlH protein migrated between the stroma and the envelope membrane; ChlH was localized on the envelope membrane, a major site of chlorophyll biosynthesis, when the Mg2+ concentration of the lysis buffer was high (above 5 mM). These results indicated that the activity of Mg-chelatase was regulated by modulation of the expression and subchloroplastic localization of ChlH protein.
Plant and Cell Physiology 04/1998; 39(3):275-84. · 4.70 Impact Factor
