potassium:proton exchanging ATPase complex / P-type potassium:proton transporter activity / Ion transport by P-type ATPases / sodium:potassium-exchanging ATPase complex / sodium ion export across plasma membrane / intracellular potassium ion homeostasis / intracellular sodium ion homeostasis / potassium ion import across plasma membrane / ATPase activator activity / potassium ion transmembrane transport ...potassium:proton exchanging ATPase complex / P-type potassium:proton transporter activity / Ion transport by P-type ATPases / sodium:potassium-exchanging ATPase complex / sodium ion export across plasma membrane / intracellular potassium ion homeostasis / intracellular sodium ion homeostasis / potassium ion import across plasma membrane / ATPase activator activity / potassium ion transmembrane transport / proton transmembrane transport / cell adhesion / apical plasma membrane / magnesium ion binding / ATP hydrolysis activity / ATP binding 類似検索 - 分子機能
ジャーナル: Nat Commun / 年: 2021 タイトル: Gastric proton pump with two occluded K engineered with sodium pump-mimetic mutations. 著者: Kazuhiro Abe / Kenta Yamamoto / Katsumasa Irie / Tomohiro Nishizawa / Atsunori Oshima / 要旨: The gastric H,K-ATPase mediates electroneutral exchange of 1H/1K per ATP hydrolysed across the membrane. Previous structural analysis of the K-occluded E2-P transition state of H,K-ATPase showed a ...The gastric H,K-ATPase mediates electroneutral exchange of 1H/1K per ATP hydrolysed across the membrane. Previous structural analysis of the K-occluded E2-P transition state of H,K-ATPase showed a single bound K at cation-binding site II, in marked contrast to the two K ions occluded at sites I and II of the closely-related Na,K-ATPase which mediates electrogenic 3Na/2K translocation across the membrane. The molecular basis of the different K stoichiometry between these K-counter-transporting pumps is elusive. We show a series of crystal structures and a cryo-EM structure of H,K-ATPase mutants with changes in the vicinity of site I, based on the structure of the sodium pump. Our step-wise and tailored construction of the mutants finally gave a two-K bound H,K-ATPase, achieved by five mutations, including amino acids directly coordinating K (Lys791Ser, Glu820Asp), indirectly contributing to cation-binding site formation (Tyr340Asn, Glu936Val), and allosterically stabilizing K-occluded conformation (Tyr799Trp). This quintuple mutant in the K-occluded E2-P state unambiguously shows two separate densities at the cation-binding site in its 2.6 Å resolution cryo-EM structure. These results offer new insights into how two closely-related cation pumps specify the number of K accommodated at their cation-binding site.