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PubMed1988

The tRNA Required for in Vitro delta-Aminolevulinic Acid Formation from Glutamate in Synechocystis Extracts : Determination of Activity in a Synechocystis in Vitro Protein Synthesizing System.

RNA is an essential component for the enzymic conversion of glutamate to delta-aminolevulinic acid (ALA), the universal heme and chlorophyll precursor, as carried out in plants, algae, and some bacteria. The RNA required in this process was reported to bear a close structural resemblance to tRNA(Glu(UUC)), and it can be isolated by affinity chromatography directed against the UUC anticodon. Affinity-purified tRNA(Glu(UUC)) from the cyanobacterium Synechocystis sp. PCC 6803 was resolved into two major subfractions by reverse-phase HPLC. Only one of these was effectively charged with glutamate in enzyme extract from Synechocystis, but both were charged in Chlorella vulgaris enzyme extract. When charged with glutamate, the two glutamyl-tRNA(Glu(UUC)) species produced were equally effective in supporting both ALA formation and protein synthesis in vitro, as measured by label transfer from [(3)H]glutamyl-tRNA to ALA and protein. These results indicate that one of the two tRNA(Glu(UUC)) species is used by Synechocystis for both protein biosynthesis and ALA formation. Both of the tRNA(Glu(UUC)) subfractions from Synechocystis supported ALA formation in Chlorella enzyme extract. Escherichia coli tRNA(Glu(UUC)) was charged with glutamate, but did not support ALA formation in Synechocystis enzyme extract. Unfractionated tRNA from Chlorella, pea, and E. coli, having been charged with [(3)H] glutamate by Chlorella enzyme extract and then re-isolated, were all able to transfer label to proteins in the Synechocystis enzyme extract.

Journal Article↗

PubMed1996

Cloning, purification and characterization of the protein subunit of ribonuclease P from the cyanobacterium Synechocystis sp. PCC 6803.

The rnpA gene from the cyanobacterium Synechocystis sp. PCC 6803, which codes for the protein subunit of ribonuclease P (RNase P), has been cloned by functional complementation of an Escherichia coli mutant. This protein had previously been characterized only in proteobacteria and gram-positive bacteria. rnpA and the closely linked rpmH gene, which code for the large subunit ribosomal protein L34, have been sequenced. The Synechocystis 6803 L34 protein is more similar to the homologous protein from some non-green chloroplasts than to the L34 protein from other bacteria. The protein subunit of RNase P from Synechocystis 6803 has been overexpressed in E. coli and purified to homogeneity. Antibodies raised against the Synechocystis 6803 RNase P protein did not recognize the homologous protein from E. coli (C5 protein). Similarly, antibodies raised against the E. coli C5 protein did not recognize significantly the Synechocystis 6803 protein. In spite of the lack of immunological cross-reactivity and the low level of sequence identity, the E. coli and Synechocystis 6803 proteins are functionally interchangeable. In enzymatic assays using either an E. coli precursor tRNA(Tyr) or a Synechocystis 6803 precursor tRNA(Gln) as substrates, we have detected RNase P activity with holoenzymes reconstituted with the RNA subunit from E. coli and the protein subunit from Synechocystis 6803 or with the RNA subunit from Synechocystis 6803 and the protein subunit from E. coli. The relative efficiency of cleavage of the different substrates is dependent on the origin of the protein subunit used to reconstitute the holoenzyme.

Amino Acid Sequence↗

PubMed1992

Regulation of Anabaena sp. strain PCC 7120 glutamine synthetase activity in a Synechocystis sp. strain PCC 6803 derivative strain bearing the Anabaena glnA gene and a mutated host glnA gene.

The glnA gene from Synechocystis sp. strain PCC 6803 was cloned by hybridization with the glnA gene from Anabaena sp. strain PCC 7120, and a deletion-insertion mutation of the Synechocystis gene was generated in vitro. A strain derived from Synechocystis sp. strain PCC 6803 which contained integrated into the chromosome, in addition to its own glnA gene, the Anabaena glnA gene was constructed. From that strain, a Synechocystis sp. glnA mutant could be obtained by transformation with the inactivated Synechocystis glnA gene; this mutant grew by using Anabaena glutamine synthetase and was not a glutamine auxotroph. A Synechocystis sp. glnA mutant could not be obtained, however, from the wild-type Synechocystis sp. The Anabaena glutamine synthetase enzyme was subject to ammonium-promoted inactivation when expressed in the Synechocystis strain but not in the Anabaena strain itself.

Anabaena↗

PubMed1999

Photomovement of the gliding cyanobacterium Synechocystis sp. PCC 6803.

Using a computerized videomicroscope motion analysis system, we investigated the photomovements of two Synechocystis sp. (PCC 6803 and ATCC 27184). Synechocystis sp. PCC 6803 displays a relatively slow gliding motion. The phototactic and photokinetic speeds of this cyanobacterium in liquid media were 5 microns/min and 15.8 microns/min, respectively, at 3 mumol/m2/s of stimulant white light. Synechocystis sp. PCC 6803 senses light direction rather than intensity for phototaxis. Synechocystis sp. ATCC 27184 showed a weak photokinesis but no phototaxis. Analysis of Synechocystis sp. ATCC 27184 suggests that the loss of phototaxis results from spontaneous mutation during several years of subculture. When directional irradiation was applied, the cell population of Synechocystis sp. PCC 6803 began to deviate from random movement and reached maximum orientation at 5 min after the onset of stimulant white light. Synechocystis sp. PCC 6803 showed high sensitivity to the stimulant white light of fluence rates as low as 0.002 mumol/m2/s. Neither 1,3-dichlorophenyldimethyl urea nor cyanide affected phototactic orientation, whereas cyanide inhibited gliding speed. This result suggests that the phototaxis of Synechocystis sp. PCC 6803 is independent of photosynthetic phosphorylation and that its gliding movement is primarily powered by oxidative phosphorylation. In the visible wavelength region, 560 nm, 660 nm and even 760 nm caused positive phototaxis. However, 360 nm light induced strikingly negative phototaxis. Therefore, at least two independent photoreceptors may exist to control phototaxis. The photoreceptor for positive phototaxis appears likely to be a phytochrome-like tetrapyrrole rather than chlorophyll a.

Agar↗

PubMed1993

Functional analysis of the two homologous psbA gene copies in Synechocystis PCC 6714 and PCC 6803.

The cyanobacteria Synechocystis 6803 and 6714 contain three genes (psbA) coding for the D1 protein. This protein is an essential subunit of photosystem II (PSII) and is the target for herbicides. We have used herbicide-resistant mutants to study the role of the two homologous copies of the psbA genes in both strains (the third copy is not expressed). Several herbicide resistance mutations map within the psbAI gene in Synechocystis 6714 (G. Ajlani et al., Plant Mol. Biol. 13 (1989): 469-479). We have looked for mutations in copy II. Results show that in Synechocystis 6714, only psbAI contains herbicide resistance mutations. Relative expression of psbAI and psbAII has been measured by analysing the proportions of resistant and sensitive D1 in the thylakoid membranes of the mutants. In normal growth conditions, 95% resistant D1 and 5% sensitive D1 were found. In high light conditions, expression of psbAII was enhanced, producing 15% sensitive D1. This enhancement is specifically due to high light and not to the decrease of D1 concentration caused by photoinhibition. Copy I of Synechocystis 6714 corresponds to copy 2 of Synechocystis 6803 since it was always psbA2 which was recombined in Synechocystis 6803 transformants. PSII of the transformant strains was found to be 95% resistant to herbicides as in resistant mutants of Synechocystis 6714.

Amino Acid Sequence↗

PubMed1991

Partial conservation of the 5' ndhE-psaC-ndhD 3' gene arrangement of chloroplasts in the cyanobacterium Synechocystis sp. PCC 6803: implications for NDH-D function in cyanobacteria and chloroplasts.

The psaC gene, which encodes the 8.9 kDa iron-sulfur containing subunit of Photosystem I, has been sequenced from Synechocystis sp. PCC 6803 and shows greater similarity to reported plant sequences than other cyanobacterial psaC sequences. The deduced amino acid sequence of the protein encoded by the Synechocystis psaC gene is identical to the tobacco PSA-C sequence. In plants psaC is located in the small single-copy region of the chloroplast genome between two genes (designated ndhE and ndhD) with similarity to genes encoding subunits of the mitochondrial NADH Dehydrogenase Complex I. The 5' ndhE-psaC-ndhD3' gene arrangement of higher plants is only partially conserved in Synechocystis. An open reading frame (ORF) upstream of the Synechocystis psaC gene has 85% identity to the tobacco ndhE gene. Downstream of psaC there is a 273 bp ORF with 48% identity to the 5' portion of the tobacco ndhD gene (1527 bp). psaC, ndhE and the region of similarity to ndhD are present in a single copy in the Synechocystis genome. Part of the wheat ndhD gene was sequenced and used as a probe for the presence of the 3' portion of the ndhD gene. The wheat ndhD probe did not hybridize to Synechocystis or Anabaena sp. PCC 7120 genomic DNA, but did hybridize to Oenothera chloroplast DNA. These results indicate the complete ndhD gene is absent in two cyanobacteria, and raises the question of what role, if any, the ndhD gene product plays in the facultative heterotroph Synechocystis sp. PCC 6803.

Amino Acid Sequence↗

PubMed2001

Two Menkes-type atpases supply copper for photosynthesis in Synechocystis PCC 6803.

Synechocystis PCC 6803 contains four genes encoding polypeptides with sequence features of CPx-type ATPases, two of which are now designated pacS and ctaA. We show that CtaA and PacS (but not the related transporters, ZiaA or CoaT) facilitate switching to the use of copper (in plastocyanin) as an alternative to iron (in cytochrome c(6)) for the carriage of electrons within the thylakoid lumen. Disruption of pacS reduced copper tolerance but enhanced silver tolerance, and pacS-mediated restoration of copper tolerance was used to select transformants. Disruption of ctaA caused no change in copper tolerance but reduced the amount of copper cell(-1). In cultures supplemented with 0.2 microm copper, photooxidation of cytochrome c(6) (PetJ) was depressed in wild-type cells but remained elevated in both Synechocystis PCC 6803(ctaA) and Synechocystis PCC 6803(pacS). Conversely, plastocyanin transcripts (petE) were less abundant in both mutants at this [copper]. Synechocystis PCC 6803(ctaA) and Synechocystis PCC 6803(pacS) showed increased iron dependence with impaired growth in deferoxamine mesylate (iron chelator)-containing media. Double mutants also deficient in cytochrome c(6), Synechocystis PCC 6803(petJ,ctaA) and Synechocystis PCC 6803(petJ,pacS), were viable, but the former had increased copper dependence with severely impaired growth in the presence of bathocuproinedisulfonic acid (copper chelator). Analogous transporters are likely to supply copper to plastocyanin in chloroplasts.

Adenosine Triphosphatases↗

PubMed2003

Expression of a cyanobacterial sucrose-phosphate synthase from Synechocystis sp. PCC 6803 in transgenic plants.

Sucrose-phosphate synthase (SPS) from the cyanobacterium Synechocystis sp. PCC 6803 lacks all of the Ser residues known to be involved in the regulation of higher plant SPS by protein phosphorylation. The Synechocystis SPS is also not allosterically regulated by glucose 6-phosphate or orthophosphate. To investigate the effects of expressing a potentially unregulated SPS in plants, the Synechocystis sps gene was introduced into tobacco, rice and tomato under the control of constitutive promoters. The Synechocystis SPS protein was expressed at a high level in the plants, which should have been sufficient to increase overall SPS activity 2-8-fold in the leaves. However, SPS activities and carbon partitioning in leaves from transgenic and wild-type plants were not significantly different. The maximal light-saturated rates of photosynthesis in leaves from tomato plants expressing the Synechocystis SPS were the same as those from wild-type plants. Tomato plants expressing the maize SPS showed 2-3-fold increases in SPS activity, increased partitioning of photoassimilate to sucrose and up to 58% higher maximal rates of photosynthesis. To investigate the apparent inactivity of the Synechocystis SPS the enzyme was purified from transgenic tobacco and rice plants. Surprisingly, the purified enzyme was found to have full catalytic activity. It is proposed that some other protein in plant cells binds to the Synechocystis SPS resulting in inhibition of the enzyme.

Allosteric Regulation↗

PubMed1996

Cloning and characterization of the chlorophyll biosynthesis gene chlM from Synechocystis PCC 6803 by complementation of a bacteriochlorophyll biosynthesis mutant of Rhodobacter capsulatus.

A bacteriochlorophyll a biosynthesis mutant of the purple photosynthetic bacterium Rhodobacter capsulatus was functionally complemented with a cosmid genomic library from Synechocystis sp. PCC 6803. The complemented R. capsulatus strain contains a defined mutation in the bchM gene that codes for Mg-protoporphyrin IX methyltransferase, the enzyme which converts Mg-protoporphyrin IX to Mg-protoporphyrin IX methylester using S-adenosyl-L-methionine as a cofactor. Since chlorophyll biosynthesis also requires the same methylation reaction, the Synechocystis genome should similarly code for a Mg-protoporphyrin IX methyltransferase. Sequence analysis of the complementing Synechocystis cosmid indicates that it contains an open reading frame exhibiting 29% sequence identity to BchM. In addition, expression of the Synechocystis gene in the R. capsulatus bchM mutant via the strong R. capsulatus puc promoter was shown to support nearly wild-type levels of bacteriochlorophyll a synthesis. To our knowledge, the Synechocystis sequence thus represents the first chlorophyll biosynthesis gene homolog of bchM. The complementing Synechocystis cosmid was also shown to code for a gene product that is a member of a highly conserved family of RNA binding proteins, the function of which in cyanobacteria remains undetermined.

Amino Acid Sequence↗

PubMed1989

Characterization of the ndhC-psbG-ORF157/159 operon of maize plastid DNA and of the cyanobacterium Synechocystis sp. PCC6803.

The ndhC and ORF159 genes of the maize plastid DNA (ptDNA) were sequenced and maize ORF159 was used to screen a library of genomic DNA of the blue-green alga Synechocystis sp. PCC 6803. The cyanobacterial gene homologous to ORF159 (ORF157) was isolated and sequenced. In sequencing the region upstream of ORF157, reading frames with homology to the ndhC and psbG genes of maize ptDNA were identified. The ndhC and psbG genes overlap in the ptDNAs of maize, tobacco and Marchantia polymorpha, but are separated by a noncoding spacer in Synechocystis. Northern blot analysis showed that the ndhC, psbG and ORF157/159 genes are cotranscribed in maize and Synechocystis. The three genes occur in the same order in ptDNA of maize, tobacco, and M. polymorpha as in Synechocystis 6803. The amino acid sequences of the NDH-C, PSII-G and the ORF157/159 proteins deduced from the maize genes are 65%, 52% and 53% homologous to those of Synechocystis. However, the cyanobacterial and higher plant NDH-C protein sequences are only 23% homologous to the mitochondrial NDH-3 protein. Protein products of in vitro transcription/translation of the Synechocystis transcription unit had apparent molecular masses of 6 kDa (NDH-C), 25 kDa (PSII-G) and 22 kDa (ORF157) on lithium dodecyl sulfate (LDS) polyacrylamide gel electrophoresis. If these are components of an NADH dehydrogenase, cyanobacteria appear to resemble mitochondria more than they do Escherichia coli and Rhodopseudomonas capsulata with regard to this enzyme complex.

Amino Acid Sequence↗

PubMed2002

Effect of increased PHA synthase activity on polyhydroxyalkanoates biosynthesis in Synechocystis sp. PCC6803.

Polyhydroxyalkanoate (PHA) synthase activity in Synechocystis sp. PCC6803 was increased two-fold by introducing the PHA biosynthetic genes of Ralstonia eutropha. The resulting recombinant Synechocystis sp. PCC6803 strain was subjected to conditions that favor PHA accumulation and the effects of various carbon sources were studied. In addition, the fine structure of both wild-type and recombinant Synechocystis sp. PCC6803 was examined using freeze-fracture electron microscopy technique. The PHA granules in the recombinant Synechocystis sp. PCC6803 were localised near the thylakoid membranes. Maximum amount of PHA accumulation was obtained in the presence of acetate, where the number of granules in the recombinant cells ranged from 4 to 6 and their sizes were in the range of 70-240 nm. In comparison to wild-type Synechocystis sp. PCC6803, recombinant cells with increased PHA synthase activity showed only a marginal increase in PHA content suggesting that PHA synthase is not the rate limiting enzyme of PHA biosynthesis in Synechocystis sp. PCC6803.

Acyltransferases↗

PubMed1997

Raman spectroscopic and light-induced kinetic characterization of a recombinant phytochrome of the cyanobacterium Synechocystis.

A phytochrome-encoding cDNA from the cyanobacterium Synechocystis has been heterologously expressed in Escherichia coli and reconstituted into functional chromoproteins by incubation with either phycocyanobilin (PCB) or phytochromobilin (PPhiB). These materials were studied by Raman spectroscopy and nanosecond flash photolysis. The Raman spectra suggest far-reaching similarities in chromophore configuration and conformation between the Pfr forms of Synechocystis phytochrome and the plant phytochromes (e.g. phyA from oat), but some differences, such as torsions around methine bridges and in hydrogen bonding interactions, in the Pr state. Synechocystis phytochrome (PCB) undergoes a multistep photoconversion reminiscent of the phyA Pr --> Pfr transformation but with different kinetics. The first process resolved is the decay of an intermediate with red-shifted absorption (relative to parent state) and a 25-micros lifetime. The next observable intermediate grows in with 300 (+/-25) micros and decays with 6-8 ms. The final state (Pfr) is formed biexponentially (450 ms, 1 s). When reconstituted with PPhiB, the first decay of this Synechocystis phytochrome is biexponential (5 and 25 micros). The growth of the second intermediate is slower (750 micros) than that in the PCB adduct whereas the decays of both species are similar. The formation of the Pfr form required fitting with three components (350 ms, 2.5 s, and 11 s). H/D Exchange in Synechocystis phytochrome (PCB) delays, by an isotope effect of 2.7, both growth (300 micros) and decay rates (6-8 ms) of the second intermediate. This effect is larger than values determined for phyA (ca. 1.2) and is characteristic of a rate-limiting proton transfer. The formation of the Pfr state of the PCB adduct of Synechocystis phytochrome shows a deuterium effect similar as phyA (ca. 1.2). Activation energies of the second intermediate in the range 0-18 degrees C are 44 (in H2O/buffer) and 48 kJ mol-1 (D2O), with essentially identical pre-exponential factors.

Apoproteins↗

PubMed2000

Increased production of zeaxanthin and other pigments by application of genetic engineering techniques to Synechocystis sp. strain PCC 6803.

The psbAII locus was used as an integration platform to overexpress genes involved in carotenoid biosynthesis in Synechocystis sp. strain PCC 6803 under the control of the strong psbAII promoter. The sequences of the genes encoding the yeast isopentenyl diphosphate isomerase (ipi) and the Synechocystis beta-carotene hydroxylase (crtR) and the linked Synechocystis genes coding for phytoene desaturase and phytoene synthase (crtP and crtB, respectively) were introduced into Synechocystis, replacing the psbAII coding sequence. Expression of ipi, crtR, and crtP and crtB led to a large increase in the corresponding transcript levels in the mutant strains, showing that the psbAII promoter can be used to drive transcription and to overexpress various genes in Synechocystis. Overexpression of crtP and crtB led to a 50% increase in the myxoxanthophyll and zeaxanthin contents in the mutant strain, whereas the beta-carotene and echinenone contents remained unchanged. Overexpression of crtR induced a 2.5-fold increase in zeaxanthin accumulation in the corresponding overexpressing mutant compared to that in the wild-type strain. In this mutant strain, zeaxanthin becomes the major pigment (more than half the total amount of carotenoid) and the beta-carotene and echinenone amounts are reduced by a factor of 2. However, overexpression of ipi did not result in a change in the carotenoid content of the mutant. To further alter the carotenoid content of Synechocystis, the crtO gene, encoding beta-carotene ketolase, which converts beta-carotene to echinenone, was disrupted in the wild type and in the overexpressing strains so that they no longer produced echinenone. In this way, by a combination of overexpression and deletion of particular genes, the carotenoid content of cyanobacteria can be altered significantly.

Bacterial Proteins↗

PubMed2002

Characterization of the norB gene, encoding nitric oxide reductase, in the nondenitrifying cyanobacterium Synechocystis sp. strain PCC6803.

A norB gene encoding a putative nitric oxide reductase is present in the genome of the nondenitrifying cyanobacterium Synechocystis sp. strain PCC6803. The gene product belongs to the quinol-oxidizing single-subunit class of nitric oxide reductases, discovered recently in the denitrifier Ralstonia eutropha. Heterologous complementation of a nitric oxide reductase-negative mutant of R. eutropha with norB from Synechocystis restored nitric oxide reductase activity. With reduced menadione as the electron donor, an enzymatic activity of 101 nmol of NO per min per mg of protein was obtained with membrane fractions of Synechocystis wild-type cells. Virtually no nitric oxide reductase activity was present in a norB-negative mutant of Synechocystis. Growing cells of this mutant are more sensitive toward NO than wild-type cells, indicating that the presence of a nitric oxide reductase is beneficial for Synechocystis when the cells are exposed to NO. Transcriptional fusions with the chloramphenicol acetyltransferase reporter gene were constructed to monitor norB expression in Synechocystis. Transcription of norB was not enhanced by the addition of the NO-generating agent sodium nitroprusside.

Bacterial Proteins↗

PubMed1991

Light-activated heterotrophic growth of the cyanobacterium Synechocystis sp. strain PCC 6803: a blue-light-requiring process.

A glucose-tolerant strain of Synechocystis sp. strain 6803 will not grow on glucose under complete darkness unless given a daily pulse of white light, typically 5 min of 40 mumol m-2 s-1 (light-pulsed conditions). The light pulse is insufficient for photoautotrophy, as glucose is required and growth yield is dependent on glucose concentration. Growth rate is independent of fluence, but growth yield is dependent on fluence, saturating at 40 to 75 mumol m-2 s-1. A Synechocystis strain 6803 psbA mutant strain grows under light-pulsed conditions at rates similar to those for the glucose-tolerant strain, indicating that photosystem II is not required for growth. The relative spectral sensitivity of the growth of light-pulsed cultures (growth only in blue light, 400 to 500 nm, maximum at 450 nm) precludes energetic contribution from cyclic electron transport around photosystem I. Pulses of long-wavelength light (i.e., 550 and 650 nm) did not support the growth of Synechocystis strain 6803 and, when supplied before or after a blue-light pulse, did not inhibit blue-light-stimulated growth of Synechocystis strain 6803. We conclude that the required blue-light pulse does not support growth via photosynthetic electron transport but appears instead to function as an environmental signal regulating heterotrophic metabolism, cell division, or other photomorphogenic processes. We have termed the growth of Synechocystis strain 6803 pulsed with light and kept otherwise in complete darkness light-activated heterotrophic growth. This observation of a blue-light requirement for the growth of Synechocystis strain 6803 represents a novel blue light effect on the growth of a cyanobacterium.

Cyanobacteria↗

PubMed2001

Role of NtcB in activation of nitrate assimilation genes in the cyanobacterium Synechocystis sp. strain PCC 6803.

In Synechocystis sp. strain PCC 6803, the genes encoding the proteins involved in nitrate assimilation are organized into two transcription units, nrtABCD-narB and nirA, the expression of which was repressed by ammonium and induced by inhibition of ammonium assimilation, suggesting involvement of NtcA in the transcriptional regulation. Under inducing conditions, expression of the two transcription units was enhanced by nitrite, suggesting regulation by NtcB, the nitrite-responsive transcriptional enhancer we previously identified in Synechococcus sp. strain PCC 7942. The slr0395 gene, which encodes a protein 47% identical to Synechococcus NtcB, was identified as the Synechocystis ntcB gene, on the basis of the inability of an slr0395 mutant to rapidly accumulate the transcripts of the nitrate assimilation genes upon induction and to respond to nitrite. While Synechococcus NtcB strictly requires nitrite for its action, Synechocystis NtcB enhanced transcription significantly even in the absence of nitrite. Whereas the Synechococcus ntcB mutant expresses the nitrate assimilation genes to a significant level in an NtcA-dependent manner, the Synechocystis ntcB mutant showed only low-level expression of the nitrate assimilation genes, indicating that NtcA by itself cannot efficiently promote expression of these genes in Synechocystis. Activities of the nitrate assimilation enzymes in the Synechocystis ntcB mutant were consequently low, being 40 to 50% of the wild-type level, and the cells grew on nitrate at a rate approximately threefold lower than that of the wild-type strain. These results showed that the contribution of NtcB to the expression of nitrate assimilation capability varies considerably among different strains of cyanobacteria.

Bacterial Proteins↗

PubMedDate not supplied

Interrelation between cyanophycin synthesis, L-arginine catabolism and photosynthesis in the cyanobacterium Synechocystis sp. strain PCC 6803.

Ultrastructural and immunocytochemical investigations gave evidence that cyanophycin (multi-L-arginyl-poly-L-aspartate) granules accumulate in the cyanobacterium Synechocystis sp. strain PCC 6803 under nutrient deficient growth conditions, especially under phosphate limitation. Besides nutrient deficiency, growth of Synechocystis PCC 6803 on L-arginine or L-asparagine as sole N-source also led to high increase of cyanophycin synthesis, while growth on the combination of L-arginine or L-asparagine with nitrate only caused minor cyanophycin accumulation. Growth of Synechocystis PCC 6803 on L-arginine as sole N-source caused substantial morphological and physiological changes, such as severe thylakoid membrane degradation with partial loss of pigments and photosynthetic activity leading to a phenotype almost like that seen under nutrient deficiency. In contrast to the wild type, the PsbO-free Synechocystis PCC 6803 mutant could grow on L-arginine as sole N-source with only minor morphological and physiological changes. Due to its fairly balanced growth, the mutant accumulated only few cyanophycin granules. L-arginine degrading activity (measured as ornithine and ammonium formation) was high in the PsbO-free mutant but not in the wild type when cells were grown on L-arginine as sole N-source. In both cells types the L-arginine degrading activity was high (although in the PsbO-free mutant about twice as high as in wild type), when cells were grown on L-arginine in combination with nitrate, and as expected very low when cells were grown on nitrate as sole N-source. Thus, net cyanophycin accumulation in Synechocystis PCC 6803 is regulated by the relative concentration of L-arginine to the total nitrogen pool, and the intracellular L-arginine concentration is greatly influenced by the activity of the L-arginine degrading enzyme system which in part is regulated by the activity status of photosystem II. These results suggest a complex interrelation between cyanophycin synthesis, L-arginine catabolism, and in addition photosynthesis in Synechocystis PCC 6803.

Arginine↗

PubMed2005

Transcriptional profiles and structural models of the Synechocystis sp. PCC 6803 Deg proteases.

The Synechocystis sp. PCC 6803 genome harbours a deg gene family consisting of three members, degP (htrA, slr1204), degQ (hhoA, sll1679) and degS (hhoB, sll1427). We studied the environmental regulation of the Synechocystis sp. PCC 6803 deg genes at the level of transcription and protein structures of the gene products to evaluate their hypothetical role in D1 protein turnover. Northern blotting showed that transcription of the deg genes is differentially regulated, supporting a view of distinct roles of Degs in cellular processes. The oligomerization state as well as the three dimensional structures of the Synechocystis sp. PCC 6803 Deg proteases were predicted based on an amino acid sequence alignment and comparison of the Deg crystal structures from human, Escherichia coli and Thermotoga maritima. The structures of the Synechocystis sp. PCC 6803 Degs resemble more the Thermotoga maritima Deg enzyme structure than the Escherichia coli one. Moreover, the structures of the LA-loops hint towards a homotrimeric form of the Synechocystis sp. PCC 6803 Deg proteases.

Amino Acid Sequence↗