STOICHIOMETRY AND SITE SPECIFICITY OF UNCOUPLING OF MITOCHONDRIAL OXIDATIVE PHOSPHORYLATION BY SALICYLANILIDE DERIVATIVES

The compound 5-chloro-3-t-butyl-2′-nitrosalicylanilide is effective at concentrations lower than any other known compound which can uncouple mitochondrial electron transport from the energy conservation reactions. In rat liver mitochondria complete loss of respiratory control and maximal stimulation of adenosine triphosphatase activity requires 0.6 and 1.0 molecule of uncoupler per respiratory chain, respectively. The release of the inhibition of respiration by azide (which is specific for electron transport at cytochrome oxidase) requires 1.35 molecules of uncoupler/respiratory chain. This titer is independent of the rate of electron flux and the rate of generation of high-energy intermediates. This salicylanilide derivative therefore binds stoichiometrically to a site which is approximately one per respiratory chain. The site is inferred (from the specificity of the azide inhibition) to be associated with the cytochrome oxidase portion of the respiratory chain. © 1969, American Chemical Society. All rights reserved.