Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of unsaturated fatty acids in membrane lipids in the tolerance of the photosynthetic machinery to salt stress was studied by comparing the desA-/desD- mutant of Synechocystis sp. PCC 6803, which contained monounsaturated fatty acids, with the wild-type strain, which contained a full complement of polyunsaturated fatty acids. In darkness, the loss of oxygen-evolving photosystem II activity in the presence of 0.5 M NaCl or 0.5 M LiCl was much more rapid in desA-/desD- cells than in wild-type cells. Oxygen-evolving activity that had been lost during incubation with 0.5 M NaCl in darkness returned when cells were transferred to conditions that allowed photosynthesis or respiration. Recovery was much greater in wild-type than in desA-/desD- cells, and it was prevented by lincomycin. Thus, the unsaturation of fatty acids is important in the tolerance of the photosynthetic machinery to salt stress. It appears also that the activity and synthesis of the Na+/H+ antiporter system might be suppressed under high-salt conditions and that this effect can be reversed, in part, by the unsaturation of fatty acids in membrane lipids.
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PMID:Genetic engineering of the unsaturation of fatty acids in membrane lipids alters the tolerance of Synechocystis to salt stress. 1031 75

The role of putative Na+/H+ antiporters encoded by nhaS1 (slr1727), nhaS3 (sll0689), nhaS4 (slr1595), and nhaS5 (slr0415) in salt stress response and internal pH regulation of the cyanobacterium Synechocystis PCC 6803 was investigated. For this purpose the mutants (single, double, and triple) impaired in genes coding for Na+/H+ antiporters were constructed using the method of interposon mutagenesis. PCR analyses of DNA demonstrated that mutations in nhaS1, nhaS4, and nhaS5 genes were segregated completely and the mutants contained only inactivated copies of the corresponding genes. Na+/H+ antiporter encoded by nhaS3 was essential for viability of Synechocystis since no completely segregated mutants were obtained. The steady-state intracellular sodium concentration and Na+/H+ antiporter activities were found to be the same in the wild type and all mutants. No differences were found in the growth rates of wild type and mutants during their cultivation in liquid media supplemented with 0.68 M or 0.85 M NaCl as well as in media buffered at pH 7.0, 8.0, or 9.0. The expression of genes coding for Na+/H+ antiporters was studied. No induction of any Na+/H+ antiporter encoding gene expression was found in wild type or single mutant cells grown under high salt or at different pH values. Nevertheless, in cells of double and triple mutants adapted to high salt or alkaline pH some of the remaining Na+/H+ antiporter encoding genes showed induction. These results might indicate that some of Na+/H+ antiporters can functionally replace each other under stress conditions in Synechocystis cells lacking the activity of more than one antiporter.
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PMID:Functional analysis of the Na+/H+ antiporter encoding genes of the cyanobacterium Synechocystis PCC 6803. 1199 56

Na+/H+ antiporters influence proton or sodium motive force across the membrane. Synechocystis sp. PCC 6803 has six genes encoding Na+/H+ antiporters, nhaS1-5 and sll0556. In this study, the function of NhaS3 was examined. NhaS3 was essential for growth of Synechocystis, and loss of nhaS3 was not complemented by expression of the Escherichia coli Na+/H+ antiporter NhaA. Membrane fractionation followed by immunoblotting as well as immunogold labeling revealed that NhaS3 was localized in the thylakoid membrane of Synechocystis. NhaS3 was shown to be functional over a pH range from pH 6.5 to 9.0 when expressed in E. coli. A reduction in the copy number of nhaS3 in the Synechocystis genome rendered the cells more sensitive to high Na+ concentrations. NhaS3 had no K+/H+ exchange activity itself but enhanced K+ uptake from the medium when expressed in an E. coli potassium uptake mutant. Expression of nhaS3 increased after shifting from low CO2 to high CO2 conditions. Expression of nhaS3 was also found to be controlled by the circadian rhythm. Gene expression peaked at the beginning of subjective night. This coincided with the time of the lowest rate of CO2 consumption caused by the ceasing of O2-evolving photosynthesis. This is the first report of a Na+/H+ antiporter localized in thylakoid membrane. Our results suggested a role of NhaS3 in the maintenance of ion homeostasis of H+, Na+, and K+ in supporting the conversion of photosynthetic products and in the supply of energy in the dark.
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PMID:Identification and characterization of the Na+/H+ antiporter Nhas3 from the thylakoid membrane of Synechocystis sp. PCC 6803. 1937 98