Clathrin-coated vesicles contain a proton translocating ATPase which is insensitive to azide but inhibited by N-ethylmaleimide. The ATP hydrolytic subunit of this proton pump has been solubilized, partially purified, and reconstituted into H+-ATPase-depleted coated vesicle membranes (Xie, X.-S., Stone, D.K., and Racker, E. (1984) J. Biol. Chem. 259, 11676-11678). In this communication we report that the entire proton transporting complex has been solubilized and purified 200-fold. The complex, when reconstituted into brain lipid liposomes, catalyzes azide-resistant, N-ethylmaleimide-sensitive H+ transport manifested as both generation of a pH gradient and an electrical gradient. The complex has an apparent molecular mass of 530 kDa.