ATP4A
Description
The ATP4A (ATPase H+/K+ transporting subunit alpha) is a protein-coding gene located on chromosome 19.
ATP4A is the catalytic subunit of the gastric H(+)/K(+) ATPase pump, responsible for transporting H(+) ions in exchange for K(+) ions across the apical membrane of parietal cells. This pump uses ATP as an energy source to pump H(+) ions into the gastric lumen while transporting K(+) ions from the lumen into the cell. The pump generates a million-fold proton gradient across the gastric parietal cell membrane, acidifying the gastric juice to a pH of 1. ATP hydrolysis is coupled to H(+) ion transfer, causing a conformational change from inward-facing (E1) to outward-facing (E2). Upon H(+) release into the stomach lumen, K(+) ion binds, returning the pump to its E1 state.
ATP4A is also known as ATP6A.
