Open AccessEnergy Conservation in the Terminal Region of the Respiratory Chain of the Methylotrophic Bacterium Methylophilus methylotrophus
Author(s) -
DAWSON Michael J.,
JONES Colin W.
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb05492.x
Subject(s) - cyanide , cytochrome , respiratory chain , cytochrome c , chemistry , periplasmic space , cytochrome c oxidase , oxidase test , biochemistry , electron transport chain , stereochemistry , biology , mitochondrion , enzyme , inorganic chemistry , escherichia coli , gene
Reduced + CO minus reduced difference spectra of respiratory membranes prepared from methanol‐limited cultures of Methylophilus methylotrophus confirm the presence of three CO‐binding cytochromes i.e. cytochromes aa 3 , o and C co . The kinetics of cyanide inhibition indicate that the respiratory chain of this organism is branched at the level of cytochrome c to two major terminal oxidases, viz. cytochromes aa 3 and o ; cytochrome C co is probably not a physiologically significant oxidase. Determination of proton and charge translocation stoichiometries (→ H + /O and → K + /O quotients) during oxidation of ascorbate‐ N,N,N ′, N ′ ‐tetramethyl‐ p ‐phenylenediamine shows that the terminal oxidase system of this organism exhibits a net inward translocation of 2e − , but no net proton translocation, when a pair of electrons are passed from cytochrome c to oxygen. The use of appropriate concentrations of cyanide to selectively inhibit cytochrorne o indicates that the overall translocation stoichiometries are achieved by the two oxidases, aa 3 and o , functioning similarly. These and other results suggest that methanol oxidase is organised as a simple redox arm with the metnanol oxidation site and the oxygen consumption site(s) on the periplasmic and cytoplasmic faces of the inner membrane respectively.