EpsE point mutations block cardiolipin-stimulated ATPase activity in vitro. Cardiolipin-stimulated ATPase activity was measured kinetically for wild type EpsE-EpsL(1–253)His6 over a period of 60 min and the individual EpsE mutants with the following mutations, R210A, R225A, R320A, R324A, R336A, R369A, R156D, R156A, and D326R, or BSA over a period of 300 min in reactions containing Mg-ATP and cardiolipin. Each protein was assayed at least three separate times, and the means ± S.E. are presented. * indicates a statistically significant difference (p < 0.05) when compared with BSA.