title: Diethylstilbestrol is a potent inhibitor of the H (+) (-)PPase but not of the H (+) (-)ATPase of Rhodospirillum rubrum chromatophores.
abstract: In RhodospiriUum rubrum chromatophores, diethylsrilbestrol inhibits the photoinduced synthesis of ATP and PPi by the membrane-bound H +-ATPase and H +-PPase, respectively. 50% inhibition of ATP synthesis is obtained at 8 μM diethylsrilbestroi in the presence of 0.13 μM BChi, while Is0 for the PPi formation is 20 μM diethylstilhestrol at the same chromatophore concentration. Diethylstilbestroi also inhibits the hydrolyricactivity of the H +-PPase, both in the membrane-bound and in the solubilized and purified state.Inhibition to 50% is already attained at 3 μM diethyistilbestrol in chromatopbores when 1 μM FCCP ispresent and the BChl-concentrarion is 0.62 μM. The hydrolysis by the solubilized enzyme has an /50 of 5 μM when 5 μg protein/ml is used. In contrast to the PPi-hydrolysis, the ATPase activity of thechromatophores shows a small activation at low diethylstiihestroi concentration and becomes inhibited at higher concentrations. Also, solubilized FoFI-ATPase is activated to a small extent by diethyisrilbestrol at the concentrations tested. At low concentrations of BChl, the inhibitory action of diethyistilhestrol on ATP and PPI synthesis can be reversed by addition of bovine serum albumin. The time dependence and inhibition dependence on the energy state of the membrane and on the BChl concentration are examined for the ATP synthesis. The mechanism of inhibition by diethylsrilbestrol is discussed.
authors: Department of Biochemistry, A rrhenius Laboratory, University of Stockholm, Stockholm, Sweden.
authors: A
authors: A
authors: Strid
authors: B F
authors: BF
authors: Nore
authors: P
authors: P
authors: Nyren
authors: M
authors: M
authors: Baltscheffsky
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000096:biosynthesis / Q000378:metabolism; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000378:metabolism; D002856:Chromatophores / Q000187:drug effects* / Q000201:enzymology; D045303:Cytochromes b / Q000378:metabolism; D004054:Diethylstilbestrol / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006868:Hydrolysis; D043564:Inorganic Pyrophosphatase / Q000096:biosynthesis / Q000378:metabolism*; D010084:Oxidation-Reduction; D012247:Rhodospirillum rubrum / Q000187:drug effects* / Q000201:enzymology; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D004054:Diethylstilbestrol; D000255:Adenosine Triphosphate; D045303:Cytochromes b; D000251:Adenosine Triphosphatases; D043564:Inorganic Pyrophosphatase