influence of the ionic conductance on the relation between electron transport and proton-motive force in intact cells of Rhodopseudomonas capsulata

• Published in: European journal of biochemistry Vol. 130; no. 3; pp. 575 - 580
• Main Authors: Clark, A.J, Cotton, N.P.J, Jackson, J.B
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.1983; Blackwell
• Subjects: Antimycin A - pharmacology; Bacteriology; Biological and medical sciences; Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone - pharmacology; Electric Conductivity; electron transport; Electron Transport - drug effects; Fundamental and applied biological sciences. Psychology; Membrane Potentials; Microbiology; Oxidation-Reduction - drug effects; Permeability, membrane transport, intracellular transport; Photosynthesis; photosynthetic bacteria; protonmotive force; Protons; Rhodopseudomonas - metabolism; Rhodopseudomonas capsulata; Active transport; Bacteria; Energy metabolism
• ISSN: 0014-2956; 1432-1033
• DOI: 10.1111/j.1432-1033.1983.tb07188.x

1 The dependence of membrane potential (ΔΦ) on the rate of respiration in darkened intact cell suspensions of Rhodopseudomonas capsulata was distinctly non‐linear: severe inhibition of respiration with either rotenone or KCN led to only a small drop in ΔΦ. 2 In the presence of 0.3 μM carbonylcyanide p‐trifluoromethoxyphenylhydrazone [CF3OPhzC(CN)2] the dependence of ΔΦ on respiratory rate became linear. Consequently, and particularly at lower concentrations of CF3OPhzC(CN)2, there was a pronounced, synergistic depression of the respiratory ΔΦ with CF3OPhzC(CN)2 and either rotenone or KCN. 3 Antimycin A, at a concentration which strongly inhibited the photosynthetic electron transport chain, only slightly lowered the light‐induced ΔΦ in anaerobic cell suspensions. Antimycin and CF3OPhzC(CN)2 synergistically lowered ΔΦ generated by illumination. 4 The light‐induced ΔΦ in anaerobic cells was only about 1.5‐times larger than the respiratory‐induced ΔΦ in darkened cells. Nevertheless it required approximately 16‐times more CF3OPhzC(CN)2 to collapse the photosynthetic ΔΦ than the respiratory ΔΦ. 5 These results are discussed with reference to theionic current/ΔΦ relation described in [J. B. Jackson (1982) FEBS Lett. 139, 139–143]. The unifying feature is that the intrinsic conductance of the cell membrane is strongly dependent on ΔΦ but the conductance due to CF3OPhzC(CN)2 is independent of ΔΦ.