title: Effects of permeant buffers on the initial time course of photophosphorylation and postillumination phosphorylation.
abstract: Permeant buffers (pyridine, imidazole, or phosphate) caused similar increases in the time required for onset of ATP synthesis in the light in the presence of valinomycin and K+; and in the illumination time required for postillumination phosphorylation with or without or without valinomycin and K+. Based on prior evidence, the minimum illumination time required for postillumination phosphorylation in thylakoid membranes is taken as a measure of the time required for formation of a transmembrane pH gradient sufficient to drive ATP synthesis. Our results are consistent with the view that, following illumination, as the transient transmembrane electric gradient decays, the establishment and maintenance of a pH gradient serves for energy transfer from the photosystems to the ATP synthase complex.
mesh_terms: D002021:Buffers; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000494:pharmacology*; D007700:Kinetics; D008027:Light; D010085:Oxidative Phosphorylation / Q000187:drug effects*; D010710:Phosphates / Q000494:pharmacology*; D010785:Photophosphorylation / Q000187:drug effects*; D010944:Plants / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology*; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D002021:Buffers; D007093:Imidazoles; D010710:Phosphates; D011725:Pyridines; D014634:Valinomycin