Disassembly and Reassembly of the Yeast Vacuolar H+-ATPase in Vivo

Abstract

The vacuolar H(+)-ATPase of the yeast Saccharomyces cerevisiae is composed of a complex of peripheral subunits (the V1 sector) attached to an integral membrane complex (the V0 sector). In the experiments described here, attachment of the V1 to the V0 sector was assessed in wild-type cells under a variety of growth conditions. Depriving the yeast cells of glucose, even for as little as 5 min, caused dissociation of approximately 70% of the assembled enzyme complexes into separate V1 and V0 subcomplexes. Restoration of glucose induced rapid and efficient reassembly of the enzyme from the previously synthesized subcomplexes. Indirect immunofluorescence microscopy and subcellular fractionation revealed detachment of the peripheral subunits from the vacuolar membrane in the absence of glucose, followed by reattachment in the presence of glucose. Rapid dissociation of vacuolar H(+)-ATPases could also be triggered by shifting cells into a variety of other carbon sources, and reassembly could be generated by addition of glucose. Disassembly and reassembly of vacuolar H(+)-ATPases in vivo may be a means of regulating organelle acidification in response to extracellular conditions, or a mechanism for assembling alternate complexes of vacuolar H(+)-ATPases in different intracellular compartments.