Crystal structure of the sodium-potassium pump.
The Na+,K+-ATPase generates electrochemical gradients for sodium and potassium that are vital to animal cells, exchanging three sodium ions for two potassium ions across the plasma membrane during each cycle of ATP hydrolysis. Here we present the X-ray crystal structure at 3.5 A resolution of the pig renal Na+,K+-ATPase with two rubidium ions bound (as potassium congeners) in an occluded state in the transmembrane part of the alpha-subunit. Several of the residues forming the cavity for rubidium/potassium occlusion in the Na+,K+-ATPase are homologous to those binding calcium in the Ca2+-ATPase of sarco(endo)plasmic reticulum. The beta- and gamma-subunits specific to the Na+,K+-ATPase are associated with transmembrane helices alphaM7/alphaM10 and alphaM9, respectively. The gamma-subunit corresponds to a fragment of the V-type ATPase c subunit. The carboxy terminus of the alpha-subunit is contained within a pocket between transmembrane helices and seems to be a novel regulatory element controlling sodium affinity, possibly influenced by the membrane potential.
Morth
J Preben
JP
Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, University of Aarhus, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
Pedersen
Bjørn P
BP
Toustrup-Jensen
Mads S
MS
Sørensen
Thomas L-M
TL
Petersen
Janne
J
Andersen
Jens Peter
JP
Vilsen
Bente
B
Nissen
Poul
P
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002414:Cations, Monovalent / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D005459:Fluorides; D007668:Kidney / Q000201:enzymology; D017616:Magnesium Compounds; D008564:Membrane Potentials; D008958:Models, Molecular; D011188:Potassium / Q000378:metabolism*; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000378:metabolism*; D013552:Swine
D002414:Cations, Monovalent; D017616:Magnesium Compounds; D021122:Protein Subunits; C031288:magnesium fluoride; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D005459:Fluorides; D011188:Potassium