Exploring the open pore of the potassium channel from Streptomyces lividans

FEBS Letters

Meuser, D.²  Wagner, R.¹  Splitt, H.²  Schrempf, H.² 

[1] Biophysik, FB Biologie/Chemie, Universität Osnabrück, 49069 Osnabrück, Germany;Angewandte Genetik der Mikroorganismen, Universität Osnabrück, 49069 Osnabrück, Germany

关键词: Block;    Ion permeation;    KcsA;    Pore;    Potassium channel;    Streptomyces lividans;    DDM;    dodecylmaltoside;    QA;    quaternary ammonium ion;    TBA;    tetrabutylammonium;    TEA;    tetraethylammonium;    THepA;    tetraheptylammonium;    THexA;    tetrahexylammonium;    TM;    transmembrane;    TMA;    tetramethylammonium;    TPrA;    tetrapropylammonium;    TPenA;    tetrapentylammonium;   

DOI  :  10.1016/S0014-5793(99)01579-3

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 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 ∼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.

【 授权许可】

Unknown