Inhibition of energy conservation reactions in chromatophores of Rhodospirillum rubrum by antibiotics |
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Authors: | Héctor Lucero Wanda IM Lescano Rubén H Vallejos |
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Institution: | 1. CEFOBI, Suipacha 531, 2000 Rosario, Argentina;2. Centro de Estudios Fotosintéticos y Bioquímicos (Consejo National de Investigaciones Científicas y Ténicas, Foundatión M. Lillo, and Universidad National de Rosario), 2000 Rosario, Argentina |
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Abstract: | The antibiotics efrapeptin and leucinostatin inhibited photosynthetic and oxidative phosphorylation and related reactions such as the dark and light ATP-Pi exchange reactions and the Mg-ATPase in Rhodospirillum rubrum chromatophores. Higher concentrations of leucinostatin were required for inhibition of the phenazine methosulfate-catalyzed photophosphorylation and light ATP-Pi exchange reaction than for the endogenous or succinate-induced photophosphorylation and dark ATP-Pi exchange reaction. Efrapeptin and leucinostatin inhibited the ATP-driven transhydrogenase while only the latter inhibited the light-driven transhydrogenase, proton gradient formation, and NAD+ reduction by succinate in chromatophores. Efrapeptin, but not leucinostatin, inhibited the soluble Ca-ATPase activity of the coupling factor obtained from chromatophores. The inhibition was competitive with ATP. It is concluded that efrapeptin is an effective energy transfer inhibitor whose site of action may be localized in the soluble coupling factor, while the effects of leucinostatin are more complex and cannot be explained as a simple uncoupling. |
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