8wa5

Cryo-EM structure of the gastric proton pump Y799W/E936Q mutant in K+-occluded (K+)E2-AlF state

spinqualitylabelsall models 8wa5, resolution 2.51Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 8wa5 is a 2 chain structure with sequence from Sus scrofa. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 2.51Å Ligands: ALF, CLR, K, MG, NAG, PCW Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function ATP4A_PIG Catalyzes the hydrolysis of ATP coupled with the exchange of H(+) and K(+) ions across the plasma membrane. Responsible for acid production in the stomach. Publication Abstract from PubMed The gastric proton pump (H(+),K(+)-ATPase) transports a proton into the stomach lumen for every K(+) ion exchanged in the opposite direction. In the lumen-facing state of the pump (E2), the pump selectively binds K(+) despite the presence of a 10-fold higher concentration of Na(+). The molecular basis for the ion selectivity of the pump is unknown. Using molecular dynamics simulations, free energy calculations, and Na(+) and K(+)-dependent ATPase activity assays, we demonstrate that the K(+) selectivity of the pump depends upon the simultaneous protonation of the acidic residues E343 and E795 in the ion-binding site. We also show that when E936 is protonated, the pump becomes Na(+) sensitive. The protonation-mimetic mutant E936Q exhibits weak Na(+)-activated ATPase activity. A 2.5-A resolution cryo-EM structure of the E936Q mutant in the K(+)-occluded E2-Pi form shows, however, no significant structural difference compared with wildtype except less-than-ideal coordination of K(+) in the mutant. The selectivity toward a specific ion correlates with a more rigid and less fluctuating ion-binding site. Despite being exposed to a pH of 1, the fundamental principle driving the K(+) ion selectivity of H(+),K(+)-ATPase is similar to that of Na(+),K(+)-ATPase: the ionization states of the acidic residues in the ion-binding sites determine ion selectivity. Unlike the Na(+),K(+)-ATPase, however, protonation of an ion-binding glutamate residue (E936) confers Na(+) sensitivity. Specific protonation of acidic residues confers K(+) selectivity to the gastric proton pump.,Madapally HV, Abe K, Dubey V, Khandelia H J Biol Chem. 2024 Jan;300(1):105542. doi: 10.1016/j.jbc.2023.105542. Epub 2023 , Dec 10. PMID:38072058 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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