The roles of the α and γ subunits in proton conduction through the Fo sector of the proton-translocating ATPase of Escherichia coli

Abstract

Previous genetic and biochemical studies have shown that the Fo sector of the Escherichia coli H+-ATPase is synthesized and assembled in a nonleaky form from plasmid-borne genes. The proton channel then appears to be opened by an interaction of F1 subunits, especially the alpha subunit, with the nonleaky Fo (Brusilow, W. S. A. (1987) J. Bacteriol. 169, 4984-4990; Solomon, K. A., and Brusilow, W. S. A. (1988) J. Biol. Chem. 263, 5402-5407). To study the role of the alpha and gamma subunits in proton conduction, we constructed an inducible alpha plasmid. In an alpha-gamma- background, the induction of alpha synthesis caused lethal proton leakiness, as assayed by the loss of respiration-dependent acridine orange fluorescence quenching of E. coli membranes. The presence of a gamma subunit counteracted the lethal effects as if gamma were blocking the opened channel.