title: Division of divalent cations into two groups in relation to their effect on the coupling of the F0F1-ATPase of Rhodospirillum rubrum to the protonmotive force.
abstract: Divalent cations are divided into two groups in relation to their ability to promote ATP synthase catalyzed reactions. In the presence of Mg2+, the following pattern rules: (i) uncoupler-stimulated ATP hydrolysis of Rhodospirillum rubrum chromatophores which shows an optimum concentration of the divalent cation; (ii) ATP-induced proton pumping in chromatophores; (iii) light-induced ATP synthesis in chromatophores; (iv) no or very low ATPase activity of purified F1-ATPase unmasked by diethylstilbestrol or n-octyl beta-D-glucopyranoside. In the presence of Ca2+, the following pattern occurs: (i) no stimulation of the ATP hydrolysis in chromatophores by carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone; (ii) no ATP-induced proton pumping; (iii) no light-induced ATP synthesis; (iv) a high ATPase activity of the purified F1-ATPase which is inhibited by diethylstilbestrol and n-octyl beta-D-glucopyranoside. Co2+, Mn2+, and Zn2+ are members of the "Mg2+-group", whereas Cd2+ is suggested to fall between the two groups. Intrinsic uncoupling of the membrane-bound ATP synthase has been suggested to account for the effect caused by Ca2+ in chloroplasts [Pick, U., & Weiss, M. (1988) Eur. J. Biochem. 173, 623-628]. Such an interpretation is consistent with our results on chromatophores. The uncoupling cannot occur at the level of the membrane since neither light-induced nor Mg-ATP-induced proton pumping is affected by Ca2+. A conformational change is suggested to be the reason for this intrinsic uncoupling, and it is proposed to be controlled by the diameters of the divalent cations (Ca2+ greater than Cd2+ greater than Mn2+ greater than Co2+ greater than Zn2+ greater than Mg2+).(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Institutionen för Biokemi, Arrheniuslaboratorierna för Naturvetenskap, Stockholms Universitet, Sweden.
authors: A
authors: A
authors: Strid
authors: P
authors: P
authors: Nyrén
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D002413:Cations, Divalent / Q000494:pharmacology*; D006868:Hydrolysis; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism; D012247:Rhodospirillum rubrum / Q000187:drug effects / Q000201:enzymology*
chemical_list: D002413:Cations, Divalent; D007473:Ion Channels; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases