Article
- The EMBO Journal (2005) 24, 4166 - 4175
- doi:10.1038/sj.emboj.7600877
Published online: 24 November 2005
Subject Categories:
3-D structural and functional characterization of the purified KATP channel complex Kir6.2–SUR1
Michael V Mikhailov1,a, Jeff D Campbell1,2,a, Heidi de Wet1, Kenju Shimomura1, Brittany Zadek1, Richard F Collins3, Mark SP Sansom2, Robert C Ford3 and Frances M Ashcroft1
- Laboratory of Physiology, University of Oxford, Oxford, UK
- Department of Biochemistry, University of Oxford, Oxford, UK
- Faculty of Life Sciences, University of Manchester, Manchester, UK
Correspondence to:
Frances M Ashcroft, Laboratory of Physiology, University of Oxford, Parks Road, OX1 3PT, UK. Tel.: +44 1865 285810; Fax: +44 1865 285813. E-mail: frances.ashcroft@physiol.ox.ac.uk
aThese authors contributed equally to the work
Received 22 August 2005; Accepted 15 October 2005
Abstract
ATP-sensitive potassium (KATP) 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 KATP channel complex composed of pore-forming Kir6.2 and regulatory SUR1 subunits, and determination of its structure at 18 Å 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.
Keywords:
- CryoEM,
- diabetes,
- KATP channel,
- Kir6.2,
- sulphonylurea receptor
