H+/K+ ATPase is a P2-type ATPase, a member of the eukaryotic class of P-type ATPases. Like the Ca2+ and the Na+/K+ ATPases, the H+/K+ ATPase functions as an α, β protomer. Unlike other eukaryotic ATPases, the H+/K+ ATPase is electroneutral, transporting one proton into the stomach lumen per potassium retrieved from the gastric lumen. As an ion pump the H+/K+ ATPase is able to transport ions against a concentration gradient using energy derived from the hydrolysis of ATP. Like all P-type ATPases, a phosphate group is transferred from adenosine triphosphate (ATP) to the H+/K+ ATPase during the transport cycle. This phosphate transfer powers a conformational change in the enzyme that helps drive ion transport.