Crystal structure of Na+, K(+)-ATPase in the Na(+)-bound state.
The Na(+), K(+)-adenosine triphosphatase (ATPase) maintains the electrochemical gradients of Na(+) and K(+) across the plasma membrane--a prerequisite for electrical excitability and secondary transport. Hitherto, structural information has been limited to K(+)-bound or ouabain-blocked forms. We present the crystal structure of a Na(+)-bound Na(+), K(+)-ATPase as determined at 4.3 Å resolution. Compared with the K(+)-bound form, large conformational changes are observed in the α subunit whereas the β and γ subunit structures are maintained. The locations of the three Na(+) sites are indicated with the unique site III at the recently suggested IIIb, as further supported by electrophysiological studies on leak currents. Extracellular release of the third Na(+) from IIIb through IIIa, followed by exchange of Na(+) for K(+) at sites I and II, is suggested.
Centre for Membrane Pumps in Cells and Disease-PUMPkin, Danish National Research Foundation, DK-8000 Aarhus, Denmark.
Maria
M
Nyblom
Hanne
H
Poulsen
Pontus
P
Gourdon
Linda
L
Reinhard
Magnus
M
Andersson
Erik
E
Lindahl
Natalya
N
Fedosova
Poul
P
Nissen
D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012964:Sodium / Q000737:chemistry*; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000235:genetics; D013552:Swine
D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase