Single mutations strongly alter the K+‐selective pore of the Kin channel KAT1

FEBS Letters

Gambale, Franco³  Dreyer, Ingo¹  Becker, Dirk¹  Palme, Klaus²  Hedrich, Rainer¹  Bregante, Monica³  Lehnen, Michaela² 

[1] Julius-von-Sachs-Institut für Biowissenschaften, Lehrstuhl Botanik I-Molekulare Pflanzenphysiologie und Biophysik, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany;Max-Delbrück-Laboratorium in der Max-Planck-Gesellschaft, Carl-von-Linne-Weg 10, D-50829 Cologne, Germany;Istituto di Cibernetica e Biofisica, CNR, Via de Marini 6, I-16149 Genoa, Italy

关键词: Gating;    Inactivation;    Pore structure;    Site-directed mutagenesis;    Voltage-dependent block;   

DOI  :  10.1016/S0014-5793(98)00694-2

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Voltage-dependent potassium uptake channels represent the major pathway for K⁺ accumulation underlying guard cell swelling and stomatal opening. The core structure of these Shaker-like channels is represented by six transmembrane domains and an amphiphilic pore-forming region between the fifth and sixth domain. To explore the effect of point mutations within the stretch of amino acids lining the K⁺ conducting pore of KAT1, an Arabidopsis thaliana guard cell K_in channel, we selected residues deep inside and in the periphery of the pore. The mutations on positions 256 and 267 strongly altered the interaction of the permeation pathway with external Ca²⁺ ions. Point mutations on position 256 in KAT1 affected the affinity towards Ca²⁺, the voltage dependence as well as kinetics of the Ca²⁺ blocking reaction. Among these T256S showed a Ca²⁺ phenotype reminiscent of an inactivation-like process, a phenomenon unknown for K_in channels so far. Mutating histidine 267 to alanine, a substitution strongly affecting C-type inactivation in Shaker, this apparent inactivation could be linked to a very slow calcium block. The mutation H267A did not affect gating but hastened the Ca²⁺ block/unblock kinetics and increased the Ca²⁺ affinity of KAT1. From the analysis of the presented data we conclude that even moderate point mutations in the pore of KAT1 seem to affect the pore geometry rather than channel gating.

【 授权许可】

Unknown