This paper gives a historical and personal account of the author's work in Rod Clayton's ... more This paper gives a historical and personal account of the author's work in Rod Clayton's laboratory, when he observed the first evidence of the two-electron gate in bacterial reaction center. Colin Wraight had independently discovered this phenomenon at the same time. The high similarity between the acceptor side of Photosystem II (PS II) and of bacterial reaction centers was one of the first proofs for a profound homology between these two photosystems.
Plants use a set of light sensors to control their growth and development in response to changes ... more Plants use a set of light sensors to control their growth and development in response to changes in ambient light. In particular, phytochromes exert their regulatory activity by switching between a biologically inactive red-light-absorbing form (Pr) and an active far-red-light absorbing form (Pfr). Recently, biochemical and genetic studies have demonstrated the occurrence of phytochrome-like proteins in photosynthetic and non-photosynthetic bacteria--but little is known about their functions. Here we report the discovery of a bacteriophytochrome located downstream from the photosynthesis gene cluster in a Bradyrhizobium strain symbiont of Aeschynomene. The synthesis of the complete photosynthetic apparatus is totally under the control of this bacteriophytochrome. A similar behaviour is observed for the closely related species Rhodopseudomonas palustris, but not for the more distant anoxygenic photosynthetic bacteria of the genus Rhodobacter, Rubrivivax or Rhodospirillum. Unlike other (bacterio)phytochromes, the carboxy-terminal domain of this bacteriophytochrome contains no histidine kinase features. This suggests a light signalling pathway involving direct protein-protein interaction with no phosphorelay cascade. This specific mechanism of regulation may represent an important ecological adaptation to optimize the plant-bacteria interaction.
SummaryBacterial cytochrome bc1‐complex encoded by the petABC operon consists of three subunits, ... more SummaryBacterial cytochrome bc1‐complex encoded by the petABC operon consists of three subunits, the Rieske iron‐sulphur protein, the b‐type cytochrome, and the c1‐type cytochrome. Disruption of the petA gene of Rubrivivax gelatinosus is not lethal under photosynthetic growth conditions. However, deletion of both petA and petB results in a photosynthesis‐deficient strain, suggesting the presence of a second gene encoding a Rieske protein and rescuing a functional cytochrome bc1‐complex in the PETA1 mutant. The corresponding petA2 gene was identified and the PETA2 mutant could also grow under photosynthetic conditions. The double mutant PETA12, however, was unable to grow photosynthetically. The presence of a photo‐induced cyclic electron transfer was tested by monitoring the kinetics of cytochrome photo‐oxidation on intact cells; the data confirm the capacity of petA2 to replace petA1 in the bc1‐complex to support photosynthesis. Soluble forms of both PetA1 and PetA2 Rieske proteins...
The pufX gene is essential for photoheterotrophic growth of the purple bacterium Rhodobacter spha... more The pufX gene is essential for photoheterotrophic growth of the purple bacterium Rhodobacter sphaeroides. In order to analyze the molecular function of the PufX membrane protein, we constructed a chromosomal pufX deletion mutant and phenotypically compared it to a pufX+ control strain and to two suppressor mutants which are able to grow photosynthetically in the absence of pufX. Using this genetic background, we confirmed that PufX is required for photoheterotrophic growth under anaerobic conditions, although all components of the photosynthetic apparatus were present in similar amounts in all strains investigated. We show that the deletion of PufX is not lethal for illuminated pufX- cells, suggesting that PufX is required for photosynthetic cell division. Since chromatophores isolated from the pufX- mutant were found to be unsealed vesicles, the role of PufX in photosynthetic energy transduction was studied in vivo. We show that PufX is essential for light-induced ATP synthesis (photophosphorylation) in anaerobically incubated cells. Measurements of absorption changes induced by a single turnover flash demonstrated that PufX is not required for electron flow through the reaction center and the cytochrome bc1 complex under anaerobic conditions. During prolonged illumination, however, PufX is essential for the generation of a sufficiently large membrane potential to allow photosynthetic growth. These in vivo results demonstrate that under anaerobic conditions PufX plays an essential role in facilitating effective interaction of the components of the photosynthetic apparatus.
The bacterium Blastochloris viridis carries one of the simplest photosynthetic systems, which inc... more The bacterium Blastochloris viridis carries one of the simplest photosynthetic systems, which includes a single light-harvesting complex that surrounds the reaction center, membrane soluble quinones, and a soluble periplasmic protein cytochrome c(2) that shuttle between the reaction center and the bc(1) complex and act as electron carriers, as well as the ATP synthase. The close arrangement of the photosynthetic membranes in Bl. viridis, along with the extremely tight arrangement of the photosystems within these membranes, raises a fundamental question about the diffusion of the electron carriers. To address this issue, we analyzed the structure and response of the Bl. viridis photosynthetic system to various light conditions, by using a combination of electron microscopy, whole-cell cryotomography, and spectroscopic methods. We demonstrate that in response to high light intensities, the ratio of both cytochrome c(2) and bc(1) complexes to the reaction centers is increased. The shorter membrane stacks, along with the notion that the bc(1) complex is located at the highly curved edges of these stacks, result in a smaller average distance between the reaction centers and the bc(1) complexes, leading to shorter pathways of cytochrome c(2) between the two complexes. Under anaerobic conditions, the slow diffusion rate is further mitigated by keeping most of the quinone pool reduced, resulting in a concentration gradient of quinols that allows for a constant supply of theses electron carriers to the bc(1) complex.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1987
... Pierre Parot a , Jean Thiery b and André Verméglio a. ... 195-229, Academic Press, New York 2... more ... Pierre Parot a , Jean Thiery b and André Verméglio a. ... 195-229, Academic Press, New York 2 Parson, WW, Schenck, CC, Blankenship, RE, Holten, D., Windsor, MW and Shank, CV (1978) in Frontiers of Biological Energetics, Vol. I, pp. ...
This paper gives a historical and personal account of the author's work in Rod Clayton's ... more This paper gives a historical and personal account of the author's work in Rod Clayton's laboratory, when he observed the first evidence of the two-electron gate in bacterial reaction center. Colin Wraight had independently discovered this phenomenon at the same time. The high similarity between the acceptor side of Photosystem II (PS II) and of bacterial reaction centers was one of the first proofs for a profound homology between these two photosystems.
Plants use a set of light sensors to control their growth and development in response to changes ... more Plants use a set of light sensors to control their growth and development in response to changes in ambient light. In particular, phytochromes exert their regulatory activity by switching between a biologically inactive red-light-absorbing form (Pr) and an active far-red-light absorbing form (Pfr). Recently, biochemical and genetic studies have demonstrated the occurrence of phytochrome-like proteins in photosynthetic and non-photosynthetic bacteria--but little is known about their functions. Here we report the discovery of a bacteriophytochrome located downstream from the photosynthesis gene cluster in a Bradyrhizobium strain symbiont of Aeschynomene. The synthesis of the complete photosynthetic apparatus is totally under the control of this bacteriophytochrome. A similar behaviour is observed for the closely related species Rhodopseudomonas palustris, but not for the more distant anoxygenic photosynthetic bacteria of the genus Rhodobacter, Rubrivivax or Rhodospirillum. Unlike other (bacterio)phytochromes, the carboxy-terminal domain of this bacteriophytochrome contains no histidine kinase features. This suggests a light signalling pathway involving direct protein-protein interaction with no phosphorelay cascade. This specific mechanism of regulation may represent an important ecological adaptation to optimize the plant-bacteria interaction.
SummaryBacterial cytochrome bc1‐complex encoded by the petABC operon consists of three subunits, ... more SummaryBacterial cytochrome bc1‐complex encoded by the petABC operon consists of three subunits, the Rieske iron‐sulphur protein, the b‐type cytochrome, and the c1‐type cytochrome. Disruption of the petA gene of Rubrivivax gelatinosus is not lethal under photosynthetic growth conditions. However, deletion of both petA and petB results in a photosynthesis‐deficient strain, suggesting the presence of a second gene encoding a Rieske protein and rescuing a functional cytochrome bc1‐complex in the PETA1 mutant. The corresponding petA2 gene was identified and the PETA2 mutant could also grow under photosynthetic conditions. The double mutant PETA12, however, was unable to grow photosynthetically. The presence of a photo‐induced cyclic electron transfer was tested by monitoring the kinetics of cytochrome photo‐oxidation on intact cells; the data confirm the capacity of petA2 to replace petA1 in the bc1‐complex to support photosynthesis. Soluble forms of both PetA1 and PetA2 Rieske proteins...
The pufX gene is essential for photoheterotrophic growth of the purple bacterium Rhodobacter spha... more The pufX gene is essential for photoheterotrophic growth of the purple bacterium Rhodobacter sphaeroides. In order to analyze the molecular function of the PufX membrane protein, we constructed a chromosomal pufX deletion mutant and phenotypically compared it to a pufX+ control strain and to two suppressor mutants which are able to grow photosynthetically in the absence of pufX. Using this genetic background, we confirmed that PufX is required for photoheterotrophic growth under anaerobic conditions, although all components of the photosynthetic apparatus were present in similar amounts in all strains investigated. We show that the deletion of PufX is not lethal for illuminated pufX- cells, suggesting that PufX is required for photosynthetic cell division. Since chromatophores isolated from the pufX- mutant were found to be unsealed vesicles, the role of PufX in photosynthetic energy transduction was studied in vivo. We show that PufX is essential for light-induced ATP synthesis (photophosphorylation) in anaerobically incubated cells. Measurements of absorption changes induced by a single turnover flash demonstrated that PufX is not required for electron flow through the reaction center and the cytochrome bc1 complex under anaerobic conditions. During prolonged illumination, however, PufX is essential for the generation of a sufficiently large membrane potential to allow photosynthetic growth. These in vivo results demonstrate that under anaerobic conditions PufX plays an essential role in facilitating effective interaction of the components of the photosynthetic apparatus.
The bacterium Blastochloris viridis carries one of the simplest photosynthetic systems, which inc... more The bacterium Blastochloris viridis carries one of the simplest photosynthetic systems, which includes a single light-harvesting complex that surrounds the reaction center, membrane soluble quinones, and a soluble periplasmic protein cytochrome c(2) that shuttle between the reaction center and the bc(1) complex and act as electron carriers, as well as the ATP synthase. The close arrangement of the photosynthetic membranes in Bl. viridis, along with the extremely tight arrangement of the photosystems within these membranes, raises a fundamental question about the diffusion of the electron carriers. To address this issue, we analyzed the structure and response of the Bl. viridis photosynthetic system to various light conditions, by using a combination of electron microscopy, whole-cell cryotomography, and spectroscopic methods. We demonstrate that in response to high light intensities, the ratio of both cytochrome c(2) and bc(1) complexes to the reaction centers is increased. The shorter membrane stacks, along with the notion that the bc(1) complex is located at the highly curved edges of these stacks, result in a smaller average distance between the reaction centers and the bc(1) complexes, leading to shorter pathways of cytochrome c(2) between the two complexes. Under anaerobic conditions, the slow diffusion rate is further mitigated by keeping most of the quinone pool reduced, resulting in a concentration gradient of quinols that allows for a constant supply of theses electron carriers to the bc(1) complex.
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1987
... Pierre Parot a , Jean Thiery b and André Verméglio a. ... 195-229, Academic Press, New York 2... more ... Pierre Parot a , Jean Thiery b and André Verméglio a. ... 195-229, Academic Press, New York 2 Parson, WW, Schenck, CC, Blankenship, RE, Holten, D., Windsor, MW and Shank, CV (1978) in Frontiers of Biological Energetics, Vol. I, pp. ...
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Papers by Andre Vermeglio