Involvement of ATP synthase residues αArg-376, βArg-182, and βLys-155 in Pi binding

αArg-376, βLys-155, and βArg-182 are catalytically important ATP synthase residues that were proposed to be involved in substrate Pi binding and subsequent steps of ATP synthesis [Senior, A.E., Nadanaciva, S. and Weber, J. (2002) Biochim. Biophys. Acta 1553, 188-211]. Here, it was shown using purified Escherichia coli F1-ATPase that whereas Pi protected wild-type from reaction with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, mutations βK155Q, βR182Q, βR182K, and αR376Q abolished protection. Therefore, in ATP synthesis initial binding of substrate Pi in open catalytic site βE is supported by each of these three residues.