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PubMed1993

Characterization of the plasmalemma ATPase from the cyanobacteria Synechococcus PCC 6311 and PCC 7942.

Biochemical properties of the ATPase from the plasma membrane of the cyanobacteria Synechococcus PCC 6311 and PCC 7942 were examined. ATPase activity associated with purified plasma membrane vesicles was strongly inhibited by 100 microM vanadate (87%), 100 microM diethylstilbestrol (70%) and 100 mM fluoride ions (83%). No inhibition was observed in the presence of dicyclohexylcarbodiimide, nitrate, azide, or molybdate. A 50% activation was observed in the presence of 50 mM KCl but none was observed in the presence of NaCl or NH4Cl. This ATPase was able to form a pH gradient, the amplitude of which was decreased by the presence of 100 microM vanadate. On Western blot of the plasmalemma proteins, no labeling was observed with a monoclonal antibody against the beta subunit of the F0-F1 ATPase, although staining was observed with the 55-kDa subunit of the thylakoid membrane ATPase. After phosphorylation of plasmalemma vesicles, by [gamma-32P]ATP, the autoradiograms of the electrophoreses, performed under acid conditions, exhibited labeling of a 110-kDa protein. The results indicated that the Synechococcus plasma membrane ATPase can be classified as a H+ translocating P-type ATPase and compared to the plant plasmalemma ATPase.

Adenosine Triphosphatases↗

PubMed1999

Sodium chloride-induced volume changes of freshwater cyanobacterium Synechococcus sp. PCC 7942 cells can be probed by chlorophyll a fluorescence.

Freshwater species of the cyanobacterial genus Synechococcus import NaCl passively, and export Na(+) actively, by means of primary and secondary extrusion mechanisms. As a result of the ion and water fluxes, cell volumes are enlarged. We show in this paper that the NaCl-induced volume enlargement of Synechococcus sp. PCC 7942 cells is attended by a rapid (k = 0.39 s(-1)) increase in chlorophyll (Chl) a fluorescence. The cell turgor threshold (measured by osmotic titration of Chl a fluorescence) was lower in the absence of NaCl (0.195 Osm kg(-1)) than in the presence of 0.4 M NaCl (0.248 Osm kg(-1)) indicating NaCl uptake by the cells. Turgor thresholds of cells suspended in NaCl-containing medium were enlarged further by protonophoric uncouplers, P-type ATPase inhibitors, and light starvation, conditions that are known to interfere with the active extrusion of Na(+) ions. Cell swelling exerts probably a regulation on the distribution of phycobilisome (PBS) excitation between photosystem II (fluorescent Chl a) and photosystem I (nonfluorescent Chl a), since it affects PBS-sensitized Chl a fluorescence, but not directly excited Chl a fluorescence. The dependence of the Chl a fluorescence of cyanobacteria on cell volumes allows probing of bioenergetic phenomena that are related to dynamic osmotic volume changes, transmembrane solute and water fluxes, plasma membrane permeabilities, and internal osmotic conditions of cyanobacterial cells. Thus, cyanobacteria may serve as quite convenient models of aquatic microorganisms in experimental studies directed toward the elucidation of perception mechanisms and defense mechanisms of water and solute stresses.

Chlorophyll↗

PubMed1993

Sec-Y protein is localized in both the cytoplasmic and thylakoid membranes in the cyanobacterium Synechococcus PCC7942.

Members of the SecY protein family mediate protein export in bacterial cells. Southern analyses showed that secY is likely a single copy gene in the cyanobacterium Synechococcus PCC7942. Then the subcellular location of the cyanobacterial SecY protein was determined; i) antiserum raised against a fusion protein between the SecY fragment and maltose binding protein were used for immunoblotting of the membrane fractions, and ii) a modified SecY protein carrying the c-Myc peptide tag was expressed in the cyanobacterial cells, and the subcellular distribution of the SecY-c-Myc fusion protein was analyzed with the anti-c-Myc antibodies. The obtained results suggest that the SecY protein is localized in the thylakoid membrane as well as the cytoplasmic membrane; the SecY protein probably mediates protein translocation across both the cytoplasmic and thylakoid membranes in Synechococcus PCC7942.

Amino Acid Sequence↗

PubMed1995

Alterations in protein synthesis in the cyanobacterium Synechococcus sp. strain PCC 6301 in response to Calendula micrantha extract with molluscicidal activity.

The response to the extract of the Egyptian wild herb Calendula micrantha, with molluscicidal activity, was examined in the unicellular cyanobacterium Synechococcus sp. strain PCC 6301. Growth and chlorophyll a of the cells were only slightly affected by low concentrations but drastically reduced by high concentrations. The rate of protein synthesis progressively decreased by increasing extract concentration. The cells preferentially induced the synthesis of a limited number of polypeptides in response to the treatment. Among the induced polypeptides were those with apparent molecular weights of 161K (161,000), 96.7K, 93.4K, 85K, 69.9K, 59K, 49K, 45K, 35K, 32.4K, 28K, 24K, 21.7K, 18K, and 16K based on their mobilities in gel electrophoresis. These initial studies suggest that the plant extract exerted certain stress which stimulated alteration in the pattern of protein synthesis in Synechococcus sp. Some of the induced polypeptides are similar to that known to occur in other stresses, especially heat-shock stress.

Bacterial Proteins↗

PubMed1994

Over-production of the D1 protein of photosystem II reaction centre in the cyanobacterium Synechococcus sp. PCC 7942.

The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacIQ repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 mumol photons m-2 s-1 in the presence of 40 or 80 micrograms/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 micrograms/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacIQ system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.

Amino Acid Sequence↗

PubMed1996

Expression of the type 2 metallothionein-like gene MT2 from Arabidopsis thaliana in Zn(2+)-metallothionein-deficient Synechococcus PCC 7942: putative role for MT2 in Zn2+ metabolism.

Zn2+ proteins pervade metabolism and are essential for gene expression. However, no proteins have been ascribed the central roles of Zn2+ donation to, or removal from, metalloproteins, or Zn2+ storage in vegetative plant tissue. In animals, such functions have been proposed for metallothioneins. Plants contain multiple metallothionein-like genes but their predicted products, which differ significantly from animal metallothioneins, remain to be isolated from vegetative tissue and their roles are uncertain. The type 2 metallothionein-like gene from Arabidopsis, MT2, was expressed under the control of Zn2+-responsive elements derived from the cyanobacterial metallothionein divergon, smt. Zn2+-dependent expression of MT2 transcripts in Synechococcus PCC 7942 was confirmed by northern analysis. The Arabidopsis MT2 gene partly complemented Zn2+ hypersensitivity in mutants of Synechococcus PCC 7942 which are functionally deficient in an endogenous Zn2+-metallothionein gene, smtA. MT2 was also expressed as a recombinant fusion protein in Escherichia coli, purified and shown to bind Zn2+ in vitro. The mean pH of half displacement of Zn2+ from MT2 was estimated to be 5.05. This suggests that MT2 has a greater affinity for Zn2+ than phytochelatins. The results presented here reveal that MT2 is capable of binding Zn2+ in vitro, conferring tolerance to elevated [Zn2+] in vivo within cyanobacteria and is likely to compete with other polypeptides for cellular Zn2+ in planta.

Amino Acid Sequence↗

PubMed1993

Genes of the R-phycocyanin II locus of marine Synechococcus spp., and comparison of protein-chromophore interactions in phycocyanins differing in bilin composition.

R-phycocyanin II (RPCII) is a recently discovered member of the phycocyanin family of photosynthetic light-harvesting proteins. Genes encoding the alpha and beta subunits of RPCII were cloned and sequenced from marine Synechococcus sp. strains WH8020 and WH8103. The deduced amino acid sequences of RPCII were compared to two other types of phycocyanin, C-phycocyanin (CPC) and phycoerythrocyanin (PEC). These three types vary in the composition of their covalently bound bilin prosthetic groups. In terms of amino acid sequence identity RPCII is highly homologous to CPC and PEC, suggesting that the known three-dimensional structures of the latter two are representative of RPCII. Thus the amino acid residues contacting the three bilins of RPCII could be inferred and compared to those in CPC and PEC. Certain residues were identified among the three phycocyanins as possibly correlating with specific bilin isomers. In overall sequence RPCII and CPC are more homologous to one another than either is to PEC. This probably reflects functional homology in the roles of RPCII and CPC in the transfer of light energy to the core of the phycobilisome, a function not attributed to PEC. The genomes of Synechococcus sp. strains WH8020, WH8103 and WH7803 share homologous open reading frames in the vicinity of RPCII genes. The nucleotide sequence extending 3' from RPCII genes in strain WH8020 revealed two open reading frames homologous to components of an alpha CPC phycocyanobilin lyase. These open reading frames may encode a lyase specific for the attachment of phycoerythrobilin to alpha RPCII.

Amino Acid Sequence↗

PubMed1994

Organization and transcription of the class I phycoerythrin genes of the marine cyanobacterium Synechococcus sp. WH7803.

The nucleotide sequences of the class I phycoerythrin (PE) alpha- and beta-subunit genes (cpeA and cpeB) from the marine cyanobacterium Synechococcus sp. WH7803 are reported. The cpeB gene is located upstream of cpeA with a separation of 56 nucleotides and the two genes are co-transcribed as a transcript of 1.3 kb, with the transcription startpoint being localized to 110-111 bp upstream of cpeB. The sequence of the promoter region bears no similarity to promoters reported for other cyanobacterial PE genes. Pentanucleotide repeats found upstream of some PE operons, particularly in the case of cyanobacterial strains capable of chromatic adaption, are not found in Synechococcus sp. WH7803; instead the sequence 5'-CGGTT-3' is repeated three times in the promoter region.

Amino Acid Sequence↗

PubMed1992

Primary structure of the Synechococcus PCC 7942 PAPS reductase gene.

The structural gene encoding a thioredoxin-dependent 5'-phosphoadenylyl sulphate (PAPS) reductase (EC 1.8.4.-) from cyanobacterium Synechococcus PCC 7942 ('Anacystis nidulans') was detected by heterologous hybridization with the cysH gene from Escherichia coli K12. The cyanobacterial gene (further called par gene) comprised 696 nt which are 57.8% homologous to the enterobacterial gene. The putative open reading frame encoded a polypeptide consisting of 232 amino acid residues (deduced molecular weight 26,635) which showed significant homologies to the polypeptide from E. coli (50.8%) and to the polypeptide from Saccharomyces cerevisiae (30.3%). A single cysteine located at the C-terminus of the polypeptide of E. coli (Cys239) was conserved in Synechococcus. Conservation of this cysteinyl residue seems indispensable for catalysis. Complementation of a cysH-deficient mutant of E. coli by the cyanobacterial gene indicated that the cloned DNA is the structural gene of the PAPS reductase.

Amino Acid Sequence↗

PubMed1995

Prolonged incubation with low concentrations of mercury alters energy transfer and chlorophyll (Chl) a protein complexes in Synechococcus 6301: changes in Chl a absorption and emission characteristics and loss of the F695 emission band.

Synechococcus PCC 6301 cells grown in the presence of low sublethal levels of (about 2 microM) mercury induced alterations in chlorophyll (Chl) a absorption without significant alterations in phycocyanin. Chl a fluorescence emission in Hg(2+)-raised cells showed a large (about 18 nm) blue shift in the peak emission. No major spectral changes in phycobilisome (PBsome) emission characteristic were noticed, indicating major structural alterations in Chl-protein complexes by incubation with Hg2+ ions. Low temperature (77K) emission spectra of cells grown in the presence of Hg2+ showed a loss of the characteristic Chl a emission band at 695 nm (F695), which is known to be linked to photosystem II photochemistry and to originate from the Chl a of core antenna polypeptide CP 47 of photosystem II. The SDS-PAGE polypeptide profile of thylakoids indicates a loss of a polypeptide(s) with a molecular mass between 40 and 60 kDa by Hg2+ incubation of cells. Our results suggest that prolonged incubation of Synechococcus 6301 cells with low concentrations of Hg2+ affects the Chl a spectral properties and the structure of Chl-protein complexes.

Chlorophyll↗

PubMed1996

Regulation and molecular structure of a circadian oscillating protein located in the cell membrane of the prokaryote Synechococcus RF-1.

When a light/light-adapted culture of Synechococcus RF-1 is exposed to a diurnal light/dark regimen, the synthesis of more than ten of its polypeptides is known to become entrained to a circadian oscillating pattern which persists for some time under free-running conditions. One of the circadian oscillating polypeptides, COP23, was found to be located in the cell membrane. The rate of COP23 synthesis is controlled at the transcription level. In addition to the protein synthesis rate, the content of COP23 also exhibited a circadian rhythm. Pulse labeling with [35S]methionine revealed that COP23 was relatively stable in an arrhythmic culture. However, the exposure of Synechococcus RF-1 to a light/dark regimen induced not only a circadian synthesis rhythm, but also a rapid degradation of COP23 protein at a defined period of time. The induction of rapid protein degradation was prevented by the presence of chloramphenicol. The gene encoding the COP23 polypeptide has been cloned and sequenced. The amino acid sequence derived from the open-reading frame revealed that a signal peptide (28 amino acids) does not appear to be part of the mature COP23. The mature COP23 does not have a membrane-associated segment, and it is suggested to be a peripheral molecule. With respect to their DNA base sequence and protein amino acid sequence, none of the proteins documented in the EMBL and PC/Gene data bases are significantly homologous with the COP23 molecule.

Amino Acid Sequence↗

PubMed1990

Structural and compositional analyses of the phycobilisomes of Synechococcus sp. PCC 7002. Analyses of the wild-type strain and a phycocyanin-less mutant constructed by interposon mutagenesis.

The phycobilisomes and phycobiliproteins of Synechococcus sp. PCC 7002 wild-type strain PR6000 have been isolated and characterized. The hemidiscoidal phycobilisomes of strain PR6000 are composed of eleven different polypeptides: phycocyanin alpha and beta subunits; allophycocyanin alpha and beta subunits; alpha subunit of allophycocyanin B; the allophycocyanin beta-subunit-like polypeptide of Mr 18,000; the linker phycobiliprotein of Mr 99,000; and non-chromophore-carrying linker polypeptides of Mr 33,000, 29,000, 9000, and 8000. Several of these polypeptides were purified to homogeneity and their amino acid compositions and amino-terminal amino acid sequences were determined. Analyses of the phycobiliproteins of Synechococcus sp. PCC 7002 were greatly facilitated by comparative studies performed with a mutant strain, PR6008, constructed to be devoid of the phycocyanin alpha and beta subunits by recombinant DNA techniques and transformation of strain PR6000. The absence of phycocyanin did not greatly affect the allophycocyanin content of the mutant strain but caused the doubling time to increase 2-7-fold depending upon the light intensity at which the cells were grown. Although intact phycobilisome cores could not be isolated from this mutant, it is probable that functionally intact cores do exist in vivo.

Amino Acid Sequence↗

PubMed1991

Identification of a genomic region that complements a temperature-sensitive, high CO2-requiring mutant of the cyanobacterium, Synechococcus sp. PCC7942.

In a temperature-sensitive, high CO2-requiring mutant of Synechococcus sp. PCC7942, the ability to fix intracellularly accumulated inorganic carbon was severely impaired at non-permissive temperature (41 degrees C). In contrast, inorganic carbon uptake and ribulose-1.5-bisphosphate carboxylase activity in the mutant were comparable to the respective values obtained with the wild-type strain. The mutant was transformed to the wild-type phenotype (ability to form colonies at non-permissive temperature under ordinary air) with the genomic DNA of the wild-type strain. A clone containing a 36 kb genomic DNA fragment of the wild-type strain complemented the mutant phenotype. The complementing activity region was associated with internal 17 kb SmaI, 15 kb HindIII, 3.8 kb BamHI and 0.87 kb PstI fragments. These 4 fragments overlapped only in a 0.4 kb HindIII-PstI region. In the transformants obtained with total genomic DNA or a plasmid containing the 3.8 kb BamHI fragment, the ability to fix intracellular inorganic carbon was restored. Southern hybridization and partial nucleotide sequence analysis indicated that the cloned genomic region was located approximately 20 kb downstream from the structural genes for subunits of ribulose-1.5-bisphosphate carboxylase/oxygenase. The cloned region was transcribed into a 0.5 kb mRNA. These results indicate that the cloned genomic region of Synechococcus sp. PCC7942 is involved in the efficient utilization of intracellular inorganic carbon for photosynthesis.

Blotting, Northern↗

PubMed1995

Structure and expression of the gene encoding ribosomal protein S1 from the cyanobacterium Synechococcus sp. strain PCC 6301: striking sequence similarity to the chloroplast ribosomal protein CS1.

We isolated a 38 kDa ssDNA-binding protein from the unicellular cyanobacterium Synechococcus sp. strain PCC 6301 and determined its N-terminal amino acid sequence. A genomic clone encoding the 38 kDa protein was isolated by using a degenerate oligonucleotide probe based on the amino acid sequence. The nucleotide sequence and predicted amino acid sequence revealed that the 38 kDa protein is 306 amino acids long and homologous to the nuclear-encoded 370 amino acid chloroplast ribosomal protein CS1 of spinach (48% identity), therefore identifying it as ribosomal protein (r-protein) S1. Cyanobacterial and chloroplast S1 proteins differ in size from Escherichia coli r-protein S1 (557 amino acids). This provides an additional evidence that cyanobacteria are closely related to chloroplasts. The Synechococcus gene rps1 encoding S1 is located 1.1 kb downstream from psbB, which encodes the photosystem II P680 chlorophyll a apoprotein. An open reading frame encoding a potential protein of 168 amino acids is present between psbB and rps1 and its deduced amino acid sequence is similar to that of E. coli hypothetical 17.2 kDa protein. Northern blot analysis showed that rps1 is transcribed as a monocistronic mRNA.

Amino Acid Sequence↗

PubMed1986

Organization and nucleotide sequence of genes encoding core components of the phycobilisomes from Synechococcus 6301.

Cyanobacteria possess specialized organelles, called phycobilisomes, which collect and transfer light energy to the reaction centres of photosystem II, in the photosynthetic membrane. Phycobilisomes consist of a central core, mainly composed of allophycocyanin, from which six rods radiate. We report here the isolation, for the first time, of three genes that encode core components of cyanobacterial phycobilisomes. The genes coding for the alpha- and beta-subunit apoproteins of allophycocyanin (apcA and apcB) were cloned from Synechococcus PCC 6301 and subjected to nucleotide sequence analysis. Dowstream of apcB, we found a third open reading frame (apcC) which, by comparison with known amino acid sequences, was assigned to L7.8c, a linker polypeptide associated with phycobiliproteins within the core of the phycobilisomes. Homologies between amino acid sequences deduced from the nucleotide sequence of the Synechococcus PCC 6301 apc genes and the amino acid sequences published for corresponding proteins either from cyanobacteria or chloroplast-like organelles of eukaryotic organisms, are 75% or more. The genetic organization of this photosynthetic gene cluster relative to that observed in the cyanelle genome of the flagellate Cyanophora paradoxa is discussed.

Amino Acid Sequence↗

PubMed1995

Purification and characterization of a Synechococcus sp. strain PCC 7942 polypeptide structurally similar to the stress-induced Dps/PexB protein of Escherichia coli.

A stable DNA/protein complex having an apparent molecular mass of approximately 150 kDa was purified from nitrate-limited cultures of the cyanobacterium Synechococcus sp. strain PCC 7942. Amino-terminal peptide sequencing indicated that the polypeptide was structurally similar to the Dps protein of Escherichia coli; Dps is also known as the product of the starvation- and stationary-phase-inducible gene, pexB. The 150-kDa complex dissociated into a 22-kDa protein monomer after boiling in 2% SDS. The 150-kDa complex preparation had approximately a 10% nucleic acid content and upon dissociation released DNA fragments that were sensitive to S1 nuclease digestion. Immunoblot data indicated that the complex accumulates during stationary phase and during nitrogen, sulfur, and phosphorus limitation. DNA-binding assays indicated that the protein nonspecifically binds both linear and supercoiled DNA. Circular dichroism spectroscopy revealed that the Synechococcus sp. Dps-like protein contains extensive regions of alpha-helical secondary structure. We propose that the 150-kDa complex represents a hexameric aggregate of the Dps-like protein complexed with single-stranded DNA and serves to bind a portion of the chromosomal DNA under nutrient-limited conditions.

Amino Acid Sequence↗

PubMed1996

Expression of mouse metallothionein in the cyanobacterium Synechococcus PCC7942.

A cDNA encoding mouse metallothionein was cloned into the shuttle vector pUc303, creating a translational fusion with the bacterial chloramphenicol acetyltransferase gene. The resulting fusion protein has been expressed in the cyanobacterium Synechococcus PCC7942. Cyanobacterial transformants expressed mouse metallothionein-specific mRNA species as detected by RNA slot blots. In addition, the transformants expressed a unique cadmium ion-binding protein corresponding to the predicted size of the mouse metallothionein fusion protein. Expression of this fusion protein conferred a two- to five-fold increase in cadmium ion tolerance and accumulation on Synechococcus PCC7942.

Animals↗

PubMed1996

Gene transfer and manipulation in the thermophilic cyanobacterium Synechococcus elongatus.

DNA can be introduced into the thermophilic cyanobacterium Synechococcus elongatus by electroporation or conjugation. Its genome can be readily manipulated through integrative transformation or by using promiscuous RSF1010-derived plasmids that can be transferred unaltered between Escherichia coli and Synechococcus elongatus. These vectors can therefore be used for in vivo studies of cyanobacterial proteins in both mesophilic and thermophilic cyanobacterial backgrounds. As a preliminary step towards the analysis of structure-function relationships of photosystem I (PSI) from this thermophile, the genes encoding the PSI subunits PsaF, PsaL, and PsaK were inactivated and shown to be non-essential in S. elongatus. In addition, PSI reaction centres were extracted from a psaL- strain exclusively as monomeric complexes.

Blotting, Southern↗