PROTON AND POTASSIUM-TRANSPORT BY H+ K+-ATPASES/

1. H+/K+-ATPases are members of the P-type ATPase multigene family, Th e prototypical H+/K+-ATPase is the protein that acidifies gastric lumi nal contents, The physiological and pharmacological significance of th is pump has led to a detailed investigation of its biochemistry and mo lecular and cell biology. 2. Recently, a number of closely related H+/ K+-ATPase isoforms have been discovered. These isoforms are present in organs other than the stomach, including the colon and kidney, where they contribute to acid-base and potassium homeostasis. The structure, expression and physiological roles of the gastric H+/K+-ATPase and ot her isoforms are reviewed.