Photoinactivation of photophosphorylation and dark ATPase in Rhodospirillum rubrum chromatophores.
Preillumination of Rhodospirillum rubrum chromatophores with strong, far-red light in the presence of phenazine methosulfate under non-phosphorylation conditions results in a selective, irreversible inactivation (typically about 70%) of photophosphorylation and of uncoupler-stimulated dark ATPase. The time course of the photoinactivation is similar to the light-on kinetics of the light-induced proton uptake in the absence of ADP. Only little photoinactivation occurs when the uncoupler carbonyl cyanide m-chlorophenyl hydrazone is present or when phenazine methosulfate is absent during the preillumination, indicating that the reaction occurs only when the membrane is energized. Phosphorylation conditions offer a practically complete protection against the photoinactivation. Inorganic phosphate, Mg2+ or ADP do not provide a significant protection against the photoinactivation, nor does ATP. The pH-dependence of the reaction(s) leading to photoinactivation may indicate that a partial reaction of the photophosphorylation process (perhaps only a conformational change of the coupling factor) precedes the photoinactivation.
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000251:Adenosine Triphosphatases / Q000378:metabolism* / Q000528:radiation effects; D000255:Adenosine Triphosphate / Q000494:pharmacology; D020130:Bacterial Chromatophores / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D003624:Darkness; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D008274:Magnesium / Q000494:pharmacology; D008773:Methylphenazonium Methosulfate / Q000494:pharmacology; D009840:Oligomycins / Q000494:pharmacology; D010710:Phosphates / Q000494:pharmacology; D010785:Photophosphorylation / Q000187:drug effects; D012247:Rhodospirillum rubrum / Q000187:drug effects / Q000378:metabolism*
D009840:Oligomycins; D010710:Phosphates; D008773:Methylphenazonium Methosulfate; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D008274:Magnesium