The α-subunit of the colonic H+,K+-ATPase assembles with β1-Na+,K+-ATPase in kidney and distal colon

Previous experiments from our laboratory (Codina, J., Kone, B. C., Delmas-Mata, J. T., and DuBose, T. D., Jr. (1996) J. Biol chem. 271, 29759-29763) demonstrated that the alpha-subunit of the colonic H+, K+-ATPase (HK alpha(2)) requires coexpression with a beta-subunit to support H+/K+ transport in a heterologous expression system (Xenopus laevis oocytes). In these studies, HK alpha(2) formed stable and functional alpha.beta complexes when coexpressed with either the rat beta(1)-subunit of the Na+, K+-ATPase or the beta-subunit of the gastric H+, K+-ATPase, suggesting that different beta-subunits may interact with HK alpha(2). The present studies tested this hypothesis by development and application of a specific antibody against HK alpha(2). peptide. Subsequently, immunoprecipitation experiments were preformed to determine if HK 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 distal colon.