REVERSIBLE ASSOCIATION BETWEEN THE V-1 AND V-0 DOMAINS OF YEAST VACUOLAR H-ATPASE IS AN UNCONVENTIONAL GLUCOSE-INDUCED EFFECT()

The yeast vacuolar H+-ATPase (V-ATPase) is a multisubunit complex resp onsible for organelle acidification. The enzyme is structurally organi zed into two major domains: a peripheral domain (V-1), containing the ATP binding sites, and an integral membrane domain (V-0), forming the proton pore. Dissociation of the V-1 and V-0 domains inhibits ATP-driv en proton pumping, and extracellular glucose concentrations regulate V -ATPase activity in vivo by regulating the extent of association betwe en the V-1 and V-0 domains. To examine the mechanism of this response, we quantitated the extent of V-ATPase assembly in a variety of mutant s with known effects on other glucose responsive processes, Glucose ef fects on V-ATPase assembly did not involve the Ras-cyclic AMP pathway, Snf1p, protein kinase C, or the general stress response protein Rts1p . Accumulation of glucose B-phosphate was insufficient to maintain or induce assembly of the V-ATPase, suggesting that further glucose metab olism is required. A transient decrease in ATP concentration with gluc ose deprivation occurs quickly enough to help trigger disassembly of t he V-ATPase, but increases in cellular ATP concentrations with glucose readdition cannot account for reassembly. Disassembly was inhibited i n two mutant enzymes lacking ATPase and proton pumping activities or i n the presence of the specific V-ATPase inhibitor, concanamycin A. We propose that glucose effects on V-ATPase assembly occur by a novel mec hanism that requires glucose metabolism beyond formation of glucose 6- phosphate and generates a signal that can be sensed efficiently only b y a catalytically competent V-ATPase.