Conformational dynamics of the KcsA potassium channel governs gating properties.
K+ channels conduct and regulate K+ flux across the cell membrane. Several crystal structures and biophysical studies of tetrameric ion channels have revealed many of the structural details of ion selectivity and gating. A narrow pore lined with four arrays of carbonyl groups is responsible for ion selectivity, whereas a conformational change of the four inner transmembrane helices (TM2) is involved in gating. We used NMR to examine full-length KcsA, a prototypical K+ channel, in its open, closed and intermediate states. These studies reveal that at least two conformational states exist both in the selectivity filter and near the C-terminal ends of the TM2 helices. In the ion-conducting open state, we observed rapid structural exchange between two conformations of the filter, presumably of low and high K+ affinity, respectively. Such measurements of millisecond-timescale dynamics reveal the basis for simultaneous ion selection and gating.
Baker
Kent A
KA
Structural Biology Laboratory, The Salk Institute, La Jolla, California 92037, USA.
Tzitzilonis
Christos
C
Kwiatkowski
Witek
W
Choe
Senyon
S
Riek
Roland
R
D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating; D008969:Molecular Sequence Data; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D048170:Streptomyces lividans / Q000378:metabolism; D013329:Structure-Activity Relationship
D001426:Bacterial Proteins; D015221:Potassium Channels; C107790:prokaryotic potassium channel; D011188:Potassium