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Query: UMLS:C1832526 (PCC)
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We have inactivated the genes encoding components of MntABC, an ABC (ATP binding cassette) transporter system for manganese in the cyanobacterium Synechocystis sp. PCC 6803. The growth rates of these mutant strains were significantly lower in a manganese-deficient medium and were restored to near normal levels upon addition of micromolar concentrations of Mn2+, indicating the presence of a second transport system for manganese in this organism. 54Mn2+ uptake experiments indicated that the MntABC transporter was induced under manganese starvation conditions, whereas the second transporter system was induced in the presence of micromolar levels of manganese. Both of these systems were nonfunctional at low temperatures and could transport trace levels of 54Mn2+, reflecting high affinity active transport. The initial rates of Mn2+ uptake for cells grown with or without manganese exhibited biphasic saturation kinetics, suggesting that Mn2+ can also be accumulated by a low affinity system in these bacteria. The kinetic parameters for the MntABC transporter system are Km = 1-3 microM and Vmax = 3-8 pmol/min.10(8) cells. Accumulation of manganese by this system was competitively inhibited by Cd2+ (Ki = 4-8 microM), Co2+ and Zn2+ (Ki = 8-15 microM). In contrast, the second high affinity system was highly specific for manganese and was not inhibited by any tested metal ion. We have also demonstrated that in this organism, photosynthetic electron transport is necessary for optimal rates of manganese uptake.
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PMID:Manganese transport in the cyanobacterium Synechocystis sp. PCC 6803. 882 46

The ggtA gene was sequenced during the analysis of a mutant of Synechocystis sp. strain PCC 6803 with impaired salt tolerance. It showed striking sequence similarities to ATP-binding proteins of binding-protein-dependent transport systems (ABC transporters). Mutants of ggtA and three neighboring reading frames were constructed by inserting an aphII gene cassette and were physiologically and genetically characterized. The ggtA insertion mutant lost its glucosylglycerol (GG) uptake ability, but its salt tolerance did not change. Therefore, it was concluded that active transport of the osmoprotective compound GG in Synechocystis is mediated by an ABC transporter. The genes for the GG-specific ABC transporter are not organized in an operon as usually found for comparable transporters, since the other insertion mutants showed normal GG transport activity. After cultivation of the ggtA mutant at high salt concentrations, significant amounts of GG were found in the cultivation medium, indicating that GG transport is mainly necessary for recovery of GG leaked through the cytoplasmic membrane. The Northern blot technique revealed increased transcription of the ggtA gene in cells adapted to higher salt concentrations, whereas in cells from basal medium, its transcription was weak.
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PMID:The ggtA gene encodes a subunit of the transport system for the osmoprotective compound glucosylglycerol in Synechocystis sp. strain PCC 6803. 900 25

The activities of uptake of thirteen 14C-labeled amino acids were determined in nine cyanobacteria, including the unicellular strains Synechococcus sp. strain PCC 7942 and Synechocystis sp. strain PCC 6803; the filamentous strain Pseudanabaena sp. strain PCC 6903, and the filamentous, heterocyst-forming strains Anabaena sp. strains PCC 7120 and PCC 7937; Nostoc sp. strains PCC 7413 and PCC 7107; Calothrix sp. strain PCC 7601 (which is a mutant unable to develop heterocysts); and Fischerella muscicola UTEX 1829. Amino acid transport mutants, selected as mutants resistant to some amino acid analogs, were isolated from the Anabaena, Nostoc, Calothrix, and Pseudanabaena strains. All of the tested cyanobacteria bear at least a neutral amino acid transport system, and some strains also bear transport systems specific for basic or acidic amino acids. Two genes, natA and natB, encoding elements (conserved component, NatA, and periplasmic binding protein, NatB) of an ABC-type permease for neutral amino acids were identified by insertional mutagenesis of strain PCC 6803 open reading frames from the recently published genomic DNA sequence of this cyanobacterium. DNA sequences homologous to natA and natB from strain PCC 6803 were detected by hybridization in eight cyanobacterial strains tested. Mutants unable to transport neutral amino acids, including natA and natB insertional mutants, accumulated in the extracellular medium a set of amino acids that always included Ala, Val, Phe, Ile, and Leu. A general role for a cyanobacterial neutral amino acid permease in recapture of hydrophobic amino acids leaked from the cells is suggested.
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PMID:Amino acid transport in taxonomically diverse cyanobacteria and identification of two genes encoding elements of a neutral amino acid permease putatively involved in recapture of leaked hydrophobic amino acids. 900 43

The gene devA of the filamentous heterocyst-form-ing cyanobacterium Anabaena sp. strain PCC 7120 encodes a protein with high similarity to ATP-binding cassettes of ABC transporters. Mutant M7 defective in the devA gene is arrested in the development of heterocysts at an early stage and is not able to fix N2 under aerobic conditions. The devA gene is differentially expressed in heterocysts. To gain a better understanding of the structural components of this putative ABC transporter, we determined the complete nucleotide sequence of the entire gene cluster. The two additional genes, named devB and devC, encode proteins with similarities to membrane fusion proteins (DevB) of several ABC exporters and to membrane-spanning proteins (DevC) of ABC transporters in general. Site-directed mutations in each of the three genes resulted in identical phenotypes. Heterocyst-specific glycolipids forming the laminated layer of the envelope were identified in lipid extracts of M7 and in the site-directed mutants. However, transmission electron microscopy revealed unequivocally that the glycolipid layer is missing in mutant M7. Ultrastructural analysis also confirmed a developmental block at an early stage of differentiation. The results of this study suggest that the devBCA operon encodes an exporter of glycolipids or of an enzyme that is necessary for the formation of the laminated layer. The hypothesis is proposed that an intact envelope could be required for further heterocyst differentiation.
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PMID:The DevBCA exporter is essential for envelope formation in heterocysts of the cyanobacterium Anabaena sp. strain PCC 7120. 957 Apr 4

Genes encoding elements of four amino acid permeases were identified by insertional inactivation of ORFs from the genomic sequence of the cyanobacterium Synechocystis sp. strain PCC 6803 whose putative products are homologous to amino acid permease proteins from other bacteria. A transport system for neutral amino acids and histidine and a transport system for basic amino acids and glutamine were identified as ABC-type transporters, whereas Na(+)-dependent transport of glutamate was found to be mediated by at least two systems, the secondary permease GltS and a TRAP-type transporter. Except for GltS, substrate specificities of the identified permeases do not match those of previously characterized systems homologous to these permeases.
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PMID:Identification of genes encoding amino acid permeases by inactivation of selected ORFs from the Synechocystis genomic sequence. 1173 93

Urea is an important nitrogen source for many microorganisms, but urea active transporters have not been characterized at a molecular level in any bacterium. Cells of Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120 exhibited the capacity to take up [14C]-urea from low-concentration (<1 microM) urea solutions. The Ks of Anabaena cells for urea was about 0.11 microM, and the observed uptake activity involved the transport and metabolism of urea. In contrast to urease, which was constitutively ex-pressed, expression of the high-affinity urea uptake activity was subjected to nitrogen control. In an Anabaena ureG (urease-) mutant, a concentrative, active transport of urea could be demonstrated. We found that a mutant of open reading frame (ORF) sll0374 from the Synechocystis genomic sequence lacked urea transport activity. This ORF encoded a conserved component of an ABC-type transporter, but it is not clustered together with any other possible transporter-encoding gene. An Anabaena homologue of sll0374, urtE, was isolated and found to be part of a cluster of genes, urtABCDE, putatively encoding all the elements of an ABC-type permease. Although the longest transcript that we could detect only covered urtABC, the impairment of urea transport by inactivation of urtA, urtB or urtE suggested that the whole gene cluster is expressed producing the urea permease. Expression was induced under nitrogen-limiting conditions, and a complex promoter regulated by the cyanobacterial global nitrogen control transcription factor NtcA was found upstream from urtA. Our work adds urea to the known substrates of the versatile class of ABC-type transporters and suggests the involvement of a transporter of this superfamily in urea scavenging by some bacteria in natural environments.
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PMID:An ABC-type, high-affinity urea permease identified in cyanobacteria. 1192 26

Manganese is recruited in microorganisms by way of ABC-type transporter systems. Here, the expression, purification and preliminary crystallographic analysis of a soluble form of the MntC solute-binding protein component of the MntABC manganese-import system from the cyanobacterium Synechococystis sp. PCC 6803 is reported. The protein (321 amino-acid residues) was expressed exclusively in inclusion bodies, which required unfolding and refolding in the presence of manganese prior to purification. The purified protein was crystallized in the presence of PEG and zinc. The crystals belong to space group P6(2)22, with unit-cell parameters a = b = 128.1, c = 90.0 A and a single molecule in the asymmetric unit. The crystals diffract to 2.6 A under cryoconditions using synchrotron radiation.
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PMID:Preliminary X-ray crystallographic analysis of a soluble form of MntC, a periplasmic manganese-binding component of an ABC-type Mn transporter from Synechocystis sp. PCC 6803. 1219 7

Mn is an essential component of the oxygen-evolving machinery of photosynthesis and is an essential cofactor of several important enzymes, such as Mn-superoxide dismutase and Mn-catalase. The availability of Mn in the environment varies, and little is known about the mechanisms for maintaining cytoplasmic Mn(2+) ion homeostasis. Using a DNA microarray, we screened knockout libraries of His kinases and response regulators of Synechocystis sp PCC 6803 to identify possible participants in this process. We identified a His kinase, ManS, which might sense the extracellular concentration of Mn(2+) ions, and a response regulator, ManR, which might regulate the expression of the mntCAB operon for the ABC-type transporter of Mn(2+) ions. Furthermore, analysis with the DNA microarray and by reverse transcription PCR suggested that ManS produces a signal that activates ManR, which represses the expression of the mntCAB operon. At low concentrations of Mn(2+) ions, ManS does not generate a signal, with resulting inactivation of ManR and subsequent expression of the mntCAB operon.
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PMID:A two-component Mn2+-sensing system negatively regulates expression of the mntCAB operon in Synechocystis. 1241 9

The rfrA gene was identified in a suppressor screen of a Synechocystis sp. PCC 6803 strain deficient in both mntC, encoding a component of an ABC transport system for manganese, and psbO, encoding the extrinsic manganese stabilizing protein of photosystem II (PSII). A spontaneous suppressor mutant (DeltaCDeltaO rfrA-Sup) has a point mutation in rfrA, which restores photosynthetic activity to the DeltamntCDeltapsbO double mutant. Manganese transport and photosynthesis are related in that manganese is essential to the function of PSII, and the state of cellular manganese availability influences the rate of oxygen evolution mediated by PSII. Oxygen evolution experiments with the DeltaCDeltaO rfrA-Sup mutant revealed that the mechanism of suppression is not through a direct modification of PSII. Instead, radioactive manganese uptake experiments indicated that RfrA is a regulator of a high affinity manganese transport system different from the more thoroughly characterized manganese ABC transport system in Synechocystis 6803. RfrA was named for the repeated five-residues domain in the amino terminus of the protein. The RFR domain defines a 16-member family in Synechocystis 6803. Predicted proteins with RFR domains have also been identified in other organisms, but RfrA is the first member of this family to be linked to a physiological process.
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PMID:Regulation of manganese uptake in Synechocystis 6803 by RfrA, a member of a novel family of proteins containing a repeated five-residues domain. 1273 93

In this report, we describe a newly developed method for isolating outer membranes from Synechocystis sp. PCC 6803 cells. The purity of the outer membrane fraction was verified by immunoblot analysis using antibodies against membrane-specific marker proteins. We investigated the protein composition of the outer membrane using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry followed by database identification. Forty-nine proteins were identified corresponding to 29 different gene products. All of the identified proteins have a putative N-terminal signal peptide. About 40% of the proteins identified represent hypothetical proteins with unknown function. Among the proteins identified are a Toc75 homologue, a protein that was initially found in the outer envelope of chloroplasts in pea, as well as TolC, putative porins, and a pilus protein. Other proteins identified include ABC transporters and GumB, which has a suggested function in carbohydrate export. A number of proteases such as HtrA were also found in the outer membrane of Synechocystis sp. PCC 6803.
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PMID:Isolation of outer membrane of Synechocystis sp. PCC 6803 and its proteomic characterization. 1499 Jun 84


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