Structural Biology

Eukaryotic Potassium Channel Structure

Science's STKE  09 Aug 2005:
Vol. 2005, Issue 296, pp. tw293
DOI: 10.1126/stke.2962005tw293

Voltage-gated K+ channels open in response to cell depolarization, reacting to the change in potential by movement of four charged Arg residues, which opens the pore and allows only K+ ions to exit the cell. X-ray crystallographic structures of bacterial channels have revealed the basis of the K+ selectivity. Forming crystals of the larger, multisubunit eukaryotic K+ channels has been more challenging, but Long et al. (see the cover and the news story by Service) now present in two papers a 2.9-angstrom-resolution crystal structure and a mechanistic analysis for eukaryotic Kv1.2 channels from the Shaker family. The crystals, which were formed by adding lipids during crystallization, include the oxido-reductase β subunit and are probably in a native, open state. The β subunits are positioned directly below the intracellular opening to the pore but far enough away to allow the K+ ions access to the pore through four large side portals. The voltage-sensor domains act as almost independent regions positioned within the membrane beside the cylindrical pore, with at least one of the charge-sensing arginines in direct contact with lipid. Movement of the voltage sensor causes pore opening through the S4-S5 linker helix, which constricts and dilates the S6 "inner" helices around the pore. This structure explains many apparently contradictory results reported to date on K+ channel structure and function.

S. B. Long, E. B. Campbell, R. MacKinnon, Crystal structure of a mammalian voltage-dependent Shaker family K+ channel. Science 309, 897-903 (2005). [Abstract] [Full Text]

S. B. Long, E. B. Campbell, R. MacKinnon, Voltage sensor of Kv1.2: Structural basis of electromechanical coupling. Science 309, 903-908 (2005). [Abstract] [Full Text]

R. F. Service, A new portrait puts potassium pore in a fresh light. Science 309, 867 (2005). [Abstract] [Full Text]