Atp4a
Function
The catalytic subunit of the gastric H(+)/K(+) ATPase pump which transports H(+) ions in exchange for K(+) ions across the apical membrane of parietal cells (PubMed:7762614). Uses ATP as an energy source to pump H(+) ions to the gastric lumen while transporting K(+) ion from the lumen into the cell (PubMed:7762614). Remarkably generates a million-fold proton gradient across the gastric parietal cell membrane, acidifying the gastric juice down to pH 1 (PubMed:10764766). Within a transport cycle, the transfer of a H(+) ion across the membrane is coupled to ATP hydrolysis and is associated with a transient phosphorylation that shifts the pump conformation from inward-facing (E1) to outward-facing state (E2). The release of the H(+) ion in the stomach lumen is followed by binding of K(+) ion converting the pump conformation back to the E1 state (By similarity) (PubMed:7762614).
Sequence Similarities
Belongs to the cation transport ATPase (P-type) (TC 3.A.3) family. Type IIC subfamily.
Tissue Specificity
Expressed in parietal cells (at protein level).
Cellular localization
- Apical cell membrane
- Multi-pass membrane protein
- Localized in the apical canalicular membrane of parietal cells (By similarity).
Alternative names
Potassium-transporting ATPase alpha chain 1, Gastric H(+)/K(+) ATPase subunit alpha, Proton pump, Atp4a