Sci. STKE, 9 August 2005
STRUCTURAL BIOLOGY Eukaryotic Potassium Channel Structure
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.
Citation: Eukaryotic Potassium Channel Structure. Sci. STKE 2005, tw293 (2005).
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