3-D structural and functional characterization of the purified KATP channel complex Kir6.2-SUR1.
ATP-sensitive potassium (K(ATP)) channels conduct potassium ions across cell membranes and thereby couple cellular energy metabolism to membrane electrical activity. Here, we report the heterologous expression and purification of a functionally active K(ATP) channel complex composed of pore-forming Kir6.2 and regulatory SUR1 subunits, and determination of its structure at 18 A resolution by single-particle electron microscopy. The purified channel shows ATP-ase activity similar to that of ATP-binding cassette proteins related to SUR1, and supports Rb(+) fluxes when reconstituted into liposomes. It has a compact structure, with four SUR1 subunits embracing a central Kir6.2 tetramer in both transmembrane and cytosolic domains. A cleft between adjacent SUR1s provides a route by which ATP may access its binding site on Kir6.2. The nucleotide-binding domains of adjacent SUR1 appear to interact, and form a large docking platform for cytosolic proteins. The structure, in combination with molecular modelling, suggests how SUR1 interacts with Kir6.2.
Mikhailov
Michael V
MV
Laboratory of Physiology, University of Oxford, Oxford, UK.
Campbell
Jeff D
JD
de Wet
Heidi
H
Shimomura
Kenju
K
Zadek
Brittany
B
Collins
Richard F
RF
Sansom
Mark S P
MS
Ford
Robert C
RC
Ashcroft
Frances M
FM
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000818:Animals; D020285:Cryoelectron Microscopy; D051379:Mice; D008969:Molecular Sequence Data; D015221:Potassium Channels / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D024661:Potassium Channels, Inwardly Rectifying / Q000737:chemistry* / Q000302:isolation & purification / Q000502:physiology* / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D051381:Rats; D011955:Receptors, Drug / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel
D018528:ATP-Binding Cassette Transporters; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D011993:Recombinant Fusion Proteins; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel; C577508:Abcc8 protein, mouse; C577509:Abcc8 protein, rat