coli F1F0 ATP Synthase Affect Its Inhibitory Properties

A collection of amino acid substitutions at residues Glu-32 and His-39 in the e subunit of the Escherichia coli F1FO ATP synthase has been constructed by cassette mutagenesis. Substitutions for residue Glu-32 appeared to cause abnormal inhibition of membrane-bound F1 ATPase activity, and replacement of His-39 by Arg, Val, and Pro affected FIFO interactions. In Escherichia coli, the F1Fo ATP synthase is composed of two complexes of subunits, F1 (ca,,B, y, 8, and e subunits) and Fo (a, b, and c subunits). The E subunit was shown to act as an intrinsic inhibitor of soluble F1 ATPase (15, 19), but it exhibits no inhibitory properties while part of the membrane-bound F1Fo complex (20). Both the binding and inhibitory properties of E are manifested in vivo, and the growth yield of cells deficient in E is lower than that of cells that completely lack the ATP synthase (11). Efforts to localize the inhibitory and F1 binding domains by deletion analysis (14) showed that the N-terminal 78 to 80 residues of e wer