title: Mechanism of potassium ion uptake by the Na(+)/K(+)-ATPase.
abstract: The Na(+)/K(+)-ATPase restores sodium (Na(+)) and potassium (K(+)) electrochemical gradients dissipated by action potentials and ion-coupled transport processes. As ions are transported, they become transiently trapped between intracellular and extracellular gates. Once the external gate opens, three Na(+) ions are released, followed by the binding and occlusion of two K(+) ions. While the mechanisms of Na(+) release have been well characterized by the study of transient Na(+) currents, smaller and faster transient currents mediated by external K(+) have been more difficult to study. Here we show that external K(+) ions travelling to their binding sites sense only a small fraction of the electric field as they rapidly and simultaneously become occluded. Consistent with these results, molecular dynamics simulations of a pump model show a wide water-filled access channel connecting the binding site to the external solution. These results suggest a mechanism of K(+) gating different from that of Na(+) occlusion.
authors.affiliation: 1] Laboratorio de Fisiología Celular, Facultad de Ciencias, Universidad de Chile, Montemar 254006, Chile [2] Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2366103, Chile.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Castillo
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Chicago, Gordon Center for Integrative Sciences, Chicago, Illinois 60637, USA.
authors.forename: Huan
authors.initials: H
authors.lastname: Rui
authors.affiliation: 1] Laboratorio de Fisiología Celular, Facultad de Ciencias, Universidad de Chile, Montemar 254006, Chile [2] Facultad de Ciencias, Universidad de Chile, Santiago 7800003, Chile.
authors.forename: Daniel
authors.initials: D
authors.lastname: Basilio
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Chicago, Gordon Center for Integrative Sciences, Chicago, Illinois 60637, USA.
authors.forename: Avisek
authors.initials: A
authors.lastname: Das
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Chicago, Gordon Center for Integrative Sciences, Chicago, Illinois 60637, USA.
authors.forename: Benoît
authors.initials: B
authors.lastname: Roux
authors.affiliation: 1] Laboratorio de Fisiología Celular, Facultad de Ciencias, Universidad de Chile, Montemar 254006, Chile [2] Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso 2366103, Chile.
authors.forename: Ramon
authors.initials: R
authors.lastname: Latorre
authors.affiliation: 1] Laboratorio de Fisiología Celular, Facultad de Ciencias, Universidad de Chile, Montemar 254006, Chile [2] Department of Biochemistry and Molecular Biology, University of Chicago, Gordon Center for Integrative Sciences, Chicago, Illinois 60637, USA.
authors.forename: Francisco
authors.initials: F
authors.lastname: Bezanilla
authors.affiliation: 1] Laboratorio de Fisiología Celular, Facultad de Ciencias, Universidad de Chile, Montemar 254006, Chile [2] Molecular Neurophysiology Section, Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Miguel
authors.initials: M
authors.lastname: Holmgren
mesh_terms: D000818:Animals; D049832:Decapodiformes; D056004:Molecular Dynamics Simulation; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium