ATPase, H+/K+ Exchanging Alpha Polypeptide (ATP4a)

ATP4a belongs to a family of P-type cation-transporting ATPases. The gastric H+, K+-ATPase is a heterodimer consisting of a high molecular weight catalytic alpha subunit and a smaller but heavily glycosylated beta subunit. This enzyme is a proton pump that catalyzes the hydrolysis of ATP coupled with the exchange of H(+) and K(+) ions across the plasma membrane. The gene is 15 kb long, contains 22 exons, and encodes a protein of 1,035 residues including the initiator methionine. The position of introns is similar to that in human sodium-potassium ATPase alpha-1 (ATP1A1) and alpha-3 (ATP1A3) subunits; however, the first introns of the 2 enzymes are difficult to align, and unlike the finding in the sodium-potassium ATPase gene, the sixth exon in the hydrogen-potassium ATPase gene is not separated by an intron.