A lysosomal proton pump turns on when glucose runs out.

Vacuolar H+-ATPase (V-ATPase) is a glucose-responsive, ATP-driven proton pump that controls the acidity of cellular organelles. Increases in glucose stimulate V-ATPase assembly and activity, and glucose deprivation triggers rapid V-ATPase disassembly and inactivation in yeast. McGuire and Forgac describe the opposite phenomenon in mammalian cells, specifically that V-ATPase assembly and activation increases when glucose is lost, raising new questions about mammalian mechanisms of energy conservation.