Exploring the open pore of the potassium channel from Streptomyces lividans.
The tetrameric potassium channel from Streptomyces lividans (KcsA) embedded in planar bilayers exhibits the following electrophysiological characteristics: (i) K+ ions can cross the pore in a highly hydrated state (nH2O > or = 6), (ii) the selectivity for K+ exceeds that for Na+ ions by 11 times, and both Ca2+ and Mg2+ are permeant, (iii) the internal side is blocked by Ba2+ ions in a voltage-dependent manner, (iv) intrinsic rectification is due to gating, depending on the direction of the electric field, (v) the internal side is pH-sensitive, and (vi) the open pore has a diameter of approximately 5.8 A. In conclusion, our results show that ion conduction and selectivity of KcsA cannot easily be reconciled with the properties deduced from the rigid crystal structure [Doyle et al., Science 280 (1998) 69-77], which must be concluded to have the pore trapped in its closed state.
Meuser
D
D
Angewandte Genetik der Mikroorganismen, Universität Osnabrück, Germany.
Splitt
H
H
Wagner
R
R
Schrempf
H
H
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D001464:Barium / Q000378:metabolism; D004594:Electrophysiology; D004926:Escherichia coli / Q000378:metabolism; D008564:Membrane Potentials; D016296:Mutagenesis; D010539:Permeability; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D011487:Protein Conformation; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D013302:Streptomyces / Q000737:chemistry*
D001426:Bacterial Proteins; D015221:Potassium Channels; D000644:Quaternary Ammonium Compounds; C107790:prokaryotic potassium channel; D001464:Barium; D011188:Potassium