On the localized coupling of respiration and phosphorylation in mitochondria

This paper is an overview of the theoretical and experimental studies performed in our laboratory to answer the question whether there exist conditions where the hypothetical mechanism of the localized coupling of respiration and phosphorylation postulated by R. Williams in 1961 operates. These studies were undertaken to verify the earlier suggestion that mitochondria may exist in two structural and functional states. Correspondingly, there are two operation modes of oxidative phosphorylation, one of which corresponds to the Williams' mechanism of localized coupling and the other, to the Mitchell's mechanism of delocalized coupling. The paper considers the principle of the energy conservation of oxidative reactions in mitochondrial membranes in the form of the thermodynamic potential of hydrogen ions (Δμsol) lacking, in part, the solvation shell. We present experimental evidence for the existence of the mechanism of localized coupling and describes the conditions favorable for its implementation. The experiments described in this paper show that the aforementioned models for proton coupling are not necessarily alternative. A conclusion is made that, depending on the particular conditions, either localized or delocalized coupling mechanisms of oxidative phosphorylation may come into operation.