Structure, subunit function and regulation of the coated vesicle and yeast vacuolar (H+)-ATPases

The vacuolar (H+)-ATPases (or V-ATPases) are ATP-dependent proton pumps that function to acidify intracellular compartments in eukaryotic cells. This acidification is essential for such processes as receptor-mediated endocytosis, intracellular targeting of lysosomal enzymes, protein processing and degradation and the coupled transport of small molecules. V-ATPases in the plasma membrane of specialized cells also function in such processes as renal acidification, bone resorption and pH homeostasis. Work from our laboratory has focused on the V-ATPases from clathrin-coated vesicles and yeast vacuoles. Structurally, the V-ATPases are composed of two domains: a peripheral complex (V-1) composed of eight different subunits (A-H) that is responsible for ATP hydrolysis and an integral complex (V-0) composed of five different subunits (a, d, c, c' and c") that is responsible for proton translocation. Electron microscopy has revealed the presence of multiple stalks connecting the V-1 and V-0 domains, and crosslinking has been used to address the arrangement of subunits in the complex. Site-directed mutagenesis has been employed to identify residues involved in ATP hydrolysis and proton translocation and to study the topology of the 100 kDa a subunit. This subunit has been shown to control intracellular targeting of the V-ATPase and to influence reversible dissociation and coupling of proton transport and ATP hydrolysis. (C) 2002 Elsevier Science B.V. All rights reserved.