Structure and regulation of insect plasma membrane H+V-ATPase

H+ V-ATPases (V-ATPases) are found in two principal locations, in endomembr anes and in plasma membranes. The plasma membrane V-ATPase from the midgut of larval Manduca sexta is the sole energizer of all transepithelial second ary transport processes. At least two properties make the lepidopteran midg ut a model tissue for studies of general aspects of V-ATPases. First, it is a rich source for purification of the enzyme and therefore for structural studies: 20 larvae provide up to 0.5 mg of holoenzyme, and soluble, cytosol ic V-1 complexes can be obtained in even greater amounts off up to 2 mg, Se cond, midgut ion-tranport processes are strictly controlled by the regulati on of the V-ATPase, which is the sole energizer of all ion transport in thi s epithelium. Recent advances in our understanding the structure of the V-1 and V-o complexes and of the regulation of the enzyme's biosynthesis and i on-transport activity will be discussed.