THE ALPHA-SUBUNIT OF THE COLONIC H-ATPASE ASSEMBLES WITH BETA(1)-NA+,K+-ATPASE IN KIDNEY AND DISTAL COLON(,K+)

Previous experiments from our laboratory (Codina, J., Kone, B. C., Del mas-Mata, J. T., and DuBose, T. D., Jr. (1996) J. Biol chem. 271, 2975 9-29763) demonstrated that the alpha-subunit of the colonic H+, K+-ATP ase (HK alpha(2)) requires coexpression with a beta-subunit to support H+/K+ transport in a heterologous expression system (Xenopus laevis o ocytes). In these studies, HK alpha(2) formed stable and functional al pha.beta complexes when coexpressed with either the rat beta(1)-subuni t of the Na+, K+-ATPase or the beta-subunit of the gastric H+, K+-ATPa se, suggesting that different beta-subunits may interact with HK alpha (2). The present studies tested this hypothesis by development and app lication of a specific antibody against HK alpha(2). peptide. Subseque ntly, immunoprecipitation experiments were preformed to determine if H K alpha(2) co-precipitates with the same beta-subunit in organs known to express HK alpha(2) protein. The data demonstrate that HK alpha(2) assembles with beta(1)-Na+, K+-ATPase in the renal medulla and in dist al colon.