| 1. |
- Selao, Tiago Toscano, et al.
(författare)
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Identification of Chromatophore Membrane Protein Complexes Formed under Different Nitrogen Availability Conditions in Rhodospirillum rubrum
- 2011
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Ingår i: Journal of Proteome Research. - : American Chemical Society (ACS). - 1535-3893 .- 1535-3907. ; 10:6, s. 2703-2714
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Tidskriftsartikel (refereegranskat)abstract
- The chromatophore membrane of the photosynthetic diazotroph Rhodospirillum rubrum is of vital importance for a number of central processes, including nitrogen fixation. Using a novel amphiphile, we have identified protein complexes present under different nitrogen availability conditions by the use of two-dimensional Blue Native/SDS-PAGE and NSI-LC-LTQ-Orbitrap mass spectrometry. We have identified several membrane protein complexes, including components of the ATP synthase, reaction center, light harvesting, and NADH dehydrogenase complexes. Additionally, we have identified differentially expressed proteins, such as subunits of the succinate dehydrogenase complex and other TCA cycle enzymes that are usually found in the cytosol, thus hinting at a possible association to the membrane in response to nitrogen deficiency. We propose a redox sensing mechanism that can influence the membrane subproteome in response to nitrogen availability.
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| 2. |
- Selao, Tiago Toscano, et al.
(författare)
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Subcellular Localization of Monoglucosyldiacylglycerol Synthase in Synechocystis sp PCC6803 and Its Unique Regulation by Lipid Environment
- 2014
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:2, s. e88153-
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of monogalactosyldiacylglycerol (GalDAG) and digalactosyldiacylglycerol (GalGalDAG), the major membrane lipids in cyanobacteria, begins with production of the intermediate precursor monoglucosyldiacylglycerol (GlcDAG), by monoglucosyldiacylglycerol synthase (MGS). In Synechocystis sp. PCC6803 (Synechocystis) this activity is catalyzed by an integral membrane protein, Sll1377 or MgdA. In silico sequence analysis revealed that cyanobacterial homologues of MgdA are highly conserved and comprise a distinct group of lipid glycosyltransferases. Global regulation of lipid synthesis in Synechocystis and, more specifically, the influence of the lipid environment on MgdA activity have not yet been fully elucidated. Therefore, we purified membrane subfractions from this organism and assayed MGS activity in vitro, with and without different lipids and other potential effectors. Sulfoquinovosyldiacylglycerol (SQDAG) potently stimulates MgdA activity, in contrast to other enzymes of a similar nature, which are activated by phosphatidylglycerol instead. Moreover, the final products of galactolipid synthesis, GalDAG and GalGalDAG, inhibited this activity. Western blotting revealed the presence of MgdA both in plasma and thylakoid membranes, with a high specific level of the MgdA protein in the plasma membrane but highest MGS activity in the thylakoid membrane. This discrepancy in the subcellular localization of enzyme activity and protein may indicate the presence of either an unknown regulator and/or an as yet unidentified MGS-type enzyme. Furthermore, the stimulation of MgdA activity by SQDAG observed here provides a new insight into regulation of the biogenesis of both sulfolipids and galactolipids in cyanobacteria.
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| 3. |
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| 4. |
- Selao, Tiago Toscano, 1982-, et al.
(författare)
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The effect of pyruvate on the metabolic regulation of nitrogenase activity in Rhodospirillum rubrum with darkness as switch-off effector
- 2010
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Ingår i: Microbiology. - 1350-0872 .- 1465-2080.
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Tidskriftsartikel (refereegranskat)abstract
- Rhodospirillum rubrum, a photosynthetic diazotroph, is able to regulate nitrogenase activity in response to environmental factors such as ammonium ions or darkness – the so-called switch-off effect. This is due to reversible modification of the Fe-protein one of the two components of nitrogenase. The signal transduction pathway(s) in this regulatory mechanism is not fully understood, especially not in the response to darkness. We have previously shown that the switch-off response and metabolic state differ between cells grown with dinitrogen or glutamate as nitrogen source, although both represent poor nitrogen sources. In this study we show that addition of pyruvate to cultures grown with glutamate as nitrogen source will lead to a switch-off response that is similar to that in cultures grown with dinitrogen. The effects are related to PII protein uridylylation and GS activity. We also show that pyruvate induces de novo protein synthesis and that pyruvate formate-lyase activity is required for activity in the dark.
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| 5. |
- Teixeira, Pedro Filipe, et al.
(författare)
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Diazotrophic growth of Rhodospirillum rubrum with 2-oxoglutarate as sole carbon source affects the regulation of nitrogen metabolism as well as the soluble proteome
- 2010
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 161:8, s. 651-659
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Tidskriftsartikel (refereegranskat)abstract
- 2-Oxoglutarate plays a central role as a signal in the regulation of nitrogen metabolism in the phototrophic diazotroph Rhodospirillum rubrum. In order to further study the role of this metabolite, we have constructed an R. rubrum strain that has the capacity to grow on 2-oxoglutarate as sole carbon source, in contrast to wild-type R. rubrum. This strain has the same growth characteristics as wild-type with malate as carbon source, but showed clear metabolic differences when 2-oxoglutarate was used. Among other things, the regulation of nitrogen metabolism is altered, which can be related to different modification profiles of the regulatory PII proteins.
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| 6. |
- Zhang, Lifang, et al.
(författare)
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Subcellular Localization of Carotenoid Biosynthesis in Synechocystis sp PCC 6803
- 2015
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:6
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Tidskriftsartikel (refereegranskat)abstract
- The biosynthesis pathway of carotenoids in cyanobacteria is partly described. However, the subcellular localization of individual steps is so far unknown. Carotenoid analysis of different membrane subfractions in Synechocystis sp. PCC6803 shows that "light" plasma membranes have a high carotenoid/protein ratio, when compared to "heavier" plasma membranes or thylakoids. The localization of CrtQ and CrtO, two well-defined carotenoid synthesis pathway enzymes in Synechocystis, was studied by epitope tagging and western blots. Both enzymes are locally more abundant in plasma membranes than in thylakoids, implying that the plasma membrane has higher synthesis rates of beta-carotene precursor molecules and echinenone.
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