Vacuolar H+ ATPase is a multisubunit motor formed from a catalytic V1 complex which mediates the hydrolysis of ATP and a membrane-spanning V0 complex which translocates H+ across the membrane. Previously found in association with the membranes of some organelles, e.g. endosomes, lysosomes and vacuoles, V-type H+ ATPases are also reported in the cell membranes of intercalated cells of the renal collecting tubule and the ruffled membranes of osteoclasts.
It was known that there are only two “a” isoforms in yeast V-type ATPases, Vph1 and Stev 1 which locate on the membranes of vacuole and endosome, respectively. Recent studies in mammalian cells show there are more isoforms found in V-ATPases, for example, the V1 is composed of A, B1, B2, C1, C2, D, E1, E2, F, G1, G2, G3, and H subunits and V0 is composed of a1, a2, a3, a4, d1, d2, c, c' e1, e2 subunits. However, what roles these isoforms play in V-ATPases in different cell types still keep unclear. Therefore, it becomes interesting to understand the relationship among these isoforms of V-ATPases in researching of the mechanism of osteoporosis.
Ochotny NM, Van Vliet A, Chan N, Yao Y, Morel M, Kartner N, von Schroeder HP, Heersche JN, Manolson MF. Effects of human a3 and a4 mutations that result in osteopetrosis and distal renal tubular acidosis on yeast V-ATPase expression and activity. J Biol Chem. 2006, ePub. download