Studies on the mechanism of oxidative phosphorylation: effects of specific F0 modifiers on ligand-induced conformation changes of F1

Abstract

Aurovertin is a fluorescent antibiotic that binds to the catalytic beta subunits of the mitochondrial F1-ATPase and inhibits ATP synthesis and hydrolysis. ATP, ADP, and membrane energization in submitochondrial particles (SMP) alter the fluorescence of F1-bound aurovertin. These fluorescence changes are considered to be in response to the conformation changes of F1-ATPase. This paper shows that the ATP-induced fluorescence change of aurovertin bound to SMP or complex V (purified ATP synthase complex F0-F1) is inhibited when these preparations are pretreated with oligomycin or N,N'-dicyclohexylcarbodiimide (DCCD). This inhibition is not seen with isolated F1-ATPase. These and other results have suggested that modifications of the DCCD-binding protein in the membrane sector (F0) of the ATP synthase complex are communicated to F1, thereby altering the binding characteristics of ATP to the beta subunits. By analogy, it is proposed that modifications (e.g., protonation/deprotonation) of the DCCD-binding protein effected by protonic energy alter the conformation of F1 and bring about the substrate/product binding changes that appear to be essential features of the mechanism and regulation of oxidative phosphorylation.