Role of a 50-57-kDa polypeptide heterodimer in the function of the clathrin-coated vesicle proton pump

Xiao Song Xie, Bill P. Crider, Yong Ming Ma, Dennis K. Stone

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30 Scopus citations


The vacuolar-type proton-translocating ATPase of clathrin-coated vesicles is composed of an integral membrane proton channel (V(B)) and a peripheral catalytic sector (V(C)). Native enzyme can catalyze the hydrolysis of both MgATP and CaATP and support proton pumping when reconstituted into liposomes. In contrast, isolated V(C) catalyzes only Ca2+-activated ATP hydrolysis and cannot support proton pumping when reconstituted into liposomes (Xie, X.-S., and Stone, D. K. (1988) J. Biol. Chem. 263, 9859-9867). We now report that solubilized isolated V(C) can be reassembled with purified V(B) to restore properties of native enzyme, including Mg2+-activated ATP hydrolysis and proton-pumping capability. Investigation of this reassembly revealed that a heterodimer, composed of polypeptides of 50 and 57 kDa, stimulates Ca2+- activated ATPase activity of isolated V(C) 2-fold and Mg2+-activated ATPase activity catalyzed by the reassembled pump 9-fold. Moreover, this heterodimer stimulated proton transport by the reassembled pump >20-fold. When separated from the proton pump, the dimer has no detectable kinase activity. Maximal stimulation occurs at a molar ratio of heterodimer to reassembled pump of 3, implying a structural, nonenzymatic mechanism. These data indicate that the 50-kDa and/or the 57-kDa polypeptide likely plays an essential and potentially regulatory role in the function of the proton-translocating ATPase of clathrin-coated vesicles.

Original languageEnglish (US)
Pages (from-to)25809-25815
Number of pages7
JournalJournal of Biological Chemistry
Issue number41
StatePublished - Oct 14 1994

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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