Journal
NATURE
Volume 466, Issue 7303, Pages 203-U73Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/nature09153
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Funding
- NIH [R01-GM57846]
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Interconversion between conductive and non-conductive forms of the K+ channel selectivity filter underlies a variety of gating events, from flicker transitions (at the microsecond timescale) to C-type inactivation (millisecond to second timescale). Here we report the crystal structure of the Streptomyces lividans K+ channel KcsA in its open-inactivated conformation and investigate the mechanism of C-type inactivation gating at the selectivity filter from channels 'trapped' in a series of partially open conformations. Five conformer classes were identified with openings ranging from 12 angstrom in closed KcsA (C alpha-C alpha distances at Thr 112) to 32 angstrom when fully open. They revealed a remarkable correlation between the degree of gate opening and the conformation and ion occupancy of the selectivity filter. We show that a gradual filter backbone reorientation leads first to a loss of the S2 ion binding site and a subsequent loss of the S3 binding site, presumably abrogating ion conduction. These structures indicate a molecular basis for C-type inactivation in K+ channels.
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