Diversity of mouse proton-translocating ATPase: presence of multiple isoforms of the C, d and G subunits.

Vacuolar-type proton-translocating ATPases (V-ATPases), multimeric proton pumps, are involved in a wide variety of physiological processes. For their diverse functions, V-ATPases utilize a specific subunit isoform(s). Here, we reported the molecular cloning and characterization of three novel subunit isoforms, C2, d2 and G3, of mouse V-ATPase. These isoforms were expressed in a tissue-specific manner, in contrast to the ubiquitously expressed C1, d1 and G1 isoforms. C2 was expressed predominantly in lung and kidney, and d2 and G3 specifically in kidney. We introduced these isoforms into yeasts lacking the corresponding genes. Although the G3 and d2 did not rescue the vmaDelta phenotype, d1 and the two C isoforms functionally complemented the Deltavma6 and Deltavma5, respectively, indicating that they are bona fide subunits of V-ATPase.