Modification of the F0 portion of the H+-translocating adenosinetriphosphatase complex of Escherichia coli by the water-soluble carbodiimide 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide and effect on the proton channeling function.

1-Ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC), a water-soluble carbodiimide, inhibited ECF1-F0 ATPase activity and proton translocation through F0 when reacted with Escherichia coli membrane vesicles. The site of modification was found to be in subunit c of the F0 portion of the enzyme but did not involve Asp-61, the site labeled by the hydrophobic carbodiimide dicyclohexylcarbodiimide (DCCD). EDC was not covalently incorporated into subunit c in contrast to DCCD. Instead, EDC promoted a cross-link between the C-terminal carboxyl group (Ala-79) and a near-neighbor phosphatidylethanolamine as evidenced by fragmentation of subunit c with cyanogen bromide followed by high-pressure liquid chromatography and thin-layer chromatography.