The amphipathic detergent lauryldimethylamine oxide (LDAO) stimulated ATP hydrolytic activity of Escherichia coli membranes and isolated ECF1 and ECF1-F0 ATPase complexes in a concentration-dependent manner. The enzyme was maximally activated 3-fold in membranes and 5-6-fold for isolated ECF1 or the ECF1-F0 complex. The maximal specific activity of activated ECF1 was 140-160 mumol of ATP hydrolyzed min-1 mg-1. The activation by LDAO was reversible. LDAO specifically released subunit delta from ECF1, generating a four subunit enzyme (alpha, beta, gamma, and epsilon subunits). The removal of subunit delta was not responsible for the stimulation of ATPase activity as evidenced by the full activation of the four subunit enzyme by LDAO. Treatment of ECF1 with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide generated a beta-epsilon cross-link in high yield [Lötscher, H.R., DeJong, C., & Capaldi, R. A. (1984) Biochemistry (accompanying paper in this issue)]. The formation of this cross-link was greatly reduced in the presence of LDAO, indicating that the detergent perturbated the interaction between epsilon and beta subunits although epsilon was not removed from the ECF1 complex. The results suggest that the interconversion of ECF1 from a low to a high ATPase activity form by LDAO is in major part due to a release of the inhibitory action of subunit epsilon on subunit beta.