Molecular determinants of gating at the potassium-channel selectivity filter.
We show that in the potassium channel KcsA, proton-dependent activation is followed by an inactivation process similar to C-type inactivation, and this process is suppressed by an E71A mutation in the pore helix. EPR spectroscopy demonstrates that the inner gate opens maximally at low pH regardless of the magnitude of the single-channel-open probability, implying that stationary gating originates mostly from rearrangements at the selectivity filter. Two E71A crystal structures obtained at 2.5 A reveal large structural excursions of the selectivity filter during ion conduction and provide a glimpse of the range of conformations available to this region of the channel during gating. These data establish a mechanistic basis for the role of the selectivity filter during channel activation and inactivation.
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22906, USA.
Julio F
JF
Cordero-Morales
Luis G
LG
Cuello
Yanxiang
Y
Zhao
Vishwanath
V
Jogini
D Marien
DM
Cortes
Benoît
B
Roux
Eduardo
E
Perozo
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055672:Static Electricity; D048170:Streptomyces lividans / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics
D001426:Bacterial Proteins; D015221:Potassium Channels; D011994:Recombinant Proteins; C107790:prokaryotic potassium channel