DISASSEMBLY AND REASSEMBLY OF THE YEAST VACUOLAR H-ATPASE IN-VIVO()

The vacuolar H+-ATPase of the yeast Saccharomyces cerevisiae is compos ed of a complex of peripheral subunits (the V-1 sector) attached to an integral membrane complex (the V-0 sector). In the experiments descri bed here, attachment of the V-1 to the V-0 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 V-1 and V-0 subcomplexes. Restoration of glucose induced rapid and efficie nt reassembly of the enzyme from the previously synthesized subcomplex es. Indirect immunofluorescence microscopy and subcellular fractionati on revealed detachment of the peripheral subunits from the vacuolar me mbrane in the absence of glucose, followed by reattachment in the pres ence 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 regul ating organelle acidification in response to extracellular conditions, or a mechanism for assembling alternate complexes of vacuolar H+-ATPa ses in different intracellular compartments.