Acid-base titration across the plasma membrane ofMicrococcus denitrificans: Factors affecting the effective proton conductance and the respiratory rate
- 96 Downloads
Pulsed acid-base titrations of suspensions ofM. denitrificans in a medium containing the permeant thiocyanate ion, or when K+ ion permeability was induced by valinomycin in a KCl medium, showed that the normal effective proton conductance of the membrane system was less than 1 μmho/cm2.
A pH-overshoot artefact was suppressed by adding carbonic anhydrase.
The effective proton conductance was increased by the uncoupler FCCP in the same concentration range as was required to stimulate respiration. Concentrations of FCCP above 1·5 μM inhibited respiration after an initial stimulation.
The effective proton conductance in presence of 2 μM FCCP was at least 17 μmho/cm2.
The quantitative relationships between the respiratory rate, the stoichiometry of respiration-driven proton translocation, and the effective proton conductance of the membrane of the cells are compatible with the suggestion that stimulation of respiration by FCCP is due to a release of back-pressure exerted by a protonmotive potential on the respiratory chain system in the membrane. Only one amongst other possible explanations of the stimulation of respiration by FCCP is, however, excluded.
KeywordsPermeability Respiration Respiratory Rate Carbonic Anhydrase Respiratory Chain
Unable to display preview. Download preview PDF.
- 2.P. Mitcheil, in:Cell Interface Reactions, H. D. Brown (ed.), Scholar's Library, New York, 1963, p. 33.Google Scholar
- 5.J. B. Jackson, A. R. Crofts, and L.-V. von Stedingk,European J. Biochem.,6 (1968) 41.Google Scholar
- 6.P. Scholes, P. Mitchell, and J. Moyle,European J. Biochem.,8 (1969) 450.Google Scholar
- 8.P. Mitchell,Chemiosomotic Coupling in Oxidative and Photosynthetic Phosphorylation, Glynn Research, Bodmin, Cornwall, 1966.Google Scholar
- 11.P. Mitchell and J. Moyle,European J. Biochem.,7 (1969) 471.Google Scholar
- 12.P. Mitchell and J. Moyle,European J. Biochem.,9 (1969) 149.Google Scholar
- 13.P. Mitchell and J. Moyle,Symp. Soc. Gen. Microbiol.,6 (1956) 150.Google Scholar
- 15.P. Mitchell,Ann. Rev. Microbiol.,13 (1959) 407.Google Scholar
- 16.S. J. D. Karlish, N. Shavit, and M. Avron,European J. Biochem.,9 (1969) 291.Google Scholar
- 18.G. Eisenman, S. M. Ciani, and G. Szabo,Federation Proc.,27 (1968) 1289.Google Scholar
- 19.P. Mitchell, in:Membrane Metabolism and Ion Transport, E. Bittar (ed.), John Wiley and Sons, London, 1970, vol.1, p. 192.Google Scholar
- 22.B. A. Newton,Symp. Soc. Gen. Microbiol.,8 (1958) 62.Google Scholar
- 25.P. Scholes and P. Mitchell, J. Bioenergetics, submitted for publication.Google Scholar