title: pH-dependent regulation of electron transport and ATP synthesis in chloroplasts.
abstract: This review is focused on pH-dependent mechanisms of regulation of photosynthetic electron transport and ATP synthesis in chloroplasts. The light-induced acidification of the thylakoid lumen is known to decelerate the plastoquinol oxidation by the cytochrome b 6 f complex, thus impeding the electron flow between photosystem II and photosystem I. Acidification of the lumen also triggers the dissipation of excess energy in the light-harvesting antenna of photosystem II, thereby protecting the photosynthetic apparatus against a solar stress. After brief description of structural and functional organization of the chloroplast electron transport chain, our attention is focused on the nature of the rate-limiting step of electron transfer between photosystem II and photosystem I. In the context of pH-dependent mechanism of photosynthetic control in chloroplasts, the mechanisms of plastoquinol oxidation by the cytochrome b 6 f complex have been considered. The light-induced alkalization of stroma is another factor of pH-dependent regulation of electron transport in chloroplasts. Alkalization of stroma induces activation of the Bassham-Benson-Calvin cycle reactions, thereby promoting efflux of electrons from photosystem I to NADP(+). The mechanisms of the light-induced activation of ATP synthase are briefly considered.
authors.affiliation: Department of Biophysics, Faculty of Physics, M. V. Lomonosov, Moscow State University, Moscow, Russia, an_tikhonov@mail.ru.
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Tikhonov
mesh_terms: D025181:ATP Synthetase Complexes / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D002736:Chloroplasts / Q000201:enzymology / Q000378:metabolism*; D004579:Electron Transport; D006863:Hydrogen-Ion Concentration; D010788:Photosynthesis
chemical_list: D000255:Adenosine Triphosphate; D025181:ATP Synthetase Complexes