title: Electrostatic Stabilization Plays a Central Role in Autoinhibitory Regulation of the Na+,K+-ATPase.
abstract: The Na+,K+-ATPase is present in the plasma membrane of all animal cells. It plays a crucial role in maintaining the Na+and K+electrochemical potential gradients across the membrane, which are essential in numerous physiological processes, e.g., nerve, muscle, and kidney function. Its cellular activity must, therefore, be under tight metabolic control. Consideration of eosin fluorescence and stopped-flow kinetic data indicates that the enzyme's E2 conformation is stabilized by electrostatic interactions, most likely between the N-terminus of the protein's catalytic α-subunit and the adjacent membrane. The electrostatic interactions can be screened by increasing ionic strength, leading to a more evenly balanced equilibrium between the E1 and E2 conformations. This represents an ideal situation for effective regulation of the Na+,K+-ATPase's enzymatic activity, because protein modifications, which perturb this equilibrium in either direction, can then easily lead to activation or inhibition. The effect of ionic strength on the E1:E2 distribution and the enzyme's kinetics can be mathematically described by the Gouy-Chapman theory of the electrical double layer. Weakening of the electrostatic interactions and a shift toward E1 causes a significant increase in the rate of phosphorylation of the enzyme by ATP. Electrostatic stabilization of the Na+,K+-ATPase's E2 conformation, thus, could play an important role in regulating the enzyme's physiological catalytic turnover.
authors.affiliation: Nanjing University, Jiangsu Sheng, China.
authors.forename: Qiucen
authors.initials: Q
authors.lastname: Jiang
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, New South Wales, Australia; Kolling Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Garcia
authors.affiliation: MEMPHYS, Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark.
authors.forename: Minwoo
authors.initials: M
authors.lastname: Han
authors.affiliation: Department of Biomedicine, University of Aarhus, Aarhus, Denmark.
authors.forename: Flemming
authors.initials: F
authors.lastname: Cornelius
authors.affiliation: Faculty of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Apell
authors.affiliation: MEMPHYS, Center for Biomembrane Physics, University of Southern Denmark, Odense, Denmark.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Khandelia
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, New South Wales, Australia. Electronic address: ronald.clarke@sydney.edu.au.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Clarke
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D056004:Molecular Dynamics Simulation; D009994:Osmolar Concentration; D010766:Phosphorylation; D011487:Protein Conformation; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D055672:Static Electricity; D013552:Swine
chemical_list: D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase