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Exploring the open pore of the potassium channel from Streptomyces lividans
Author(s) -
Meuser D.,
Splitt H.,
Wagner R.,
Schrempf H.
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)01579-3
Subject(s) - kcsa potassium channel , chemistry , ion , potassium channel , gating , potassium , ion channel , crystallography , membrane potential , selectivity , ion transporter , biophysics , stereochemistry , biochemistry , organic chemistry , receptor , biology , catalysis
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 ( n H2O ≳6), (ii) the selectivity for K + exceeds that for Na + ions by 11 times, and both Ca 2+ and Mg 2+ are permeant, (iii) the internal side is blocked by Ba 2+ 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 ∼5.8 Å. 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.