Susceptibility of the guard-cell K+-uptake channel KST1 to Zn2+ requires histidine residues in the S3-S4 linker and in the channel pore |
| |
Authors: | Stefan Hoth Rainer Hedrich |
| |
Affiliation: | (1) Julius-von-Sachs-Institut für Biowissenschaften, Lehrstuhl Botanik I, Molekulare Pflanzenphysiologie und Biophysik, Julius-von-Sachs-Platz 2, D-97082 Würzburg, Germany, DE |
| |
Abstract: | Potassium channels are inhibited by several mono- and divalent cations. To identify sites involved in the interaction between K+ channels and cationic effectors, we expressed the potato (Solanum tuberosum L.) guard-cell K+-uptake channel KST1 in Xenopus oocytes. This channel was reversibly blocked by extracellular Zn2+ in the micromolar range. In the presence of this heavy metal, steady-state currents were reduced in a pH-dependent but voltage-independent manner. Since Zn2+-inhibition was less effective at elevated external proton concentrations, we generated alanine mutants with respect to both extracellular histidines in KST1. Whereas substitution of the pore histidine H271 resulted in a reduced blockade by Zn2+, the channel mutant KST1-H160A in the S3-S4 linker lost most of its Zn2+ sensitivity. Since both histidines alter the susceptibility of KST1 to Zn2+, the block may predominantly result from these two sites. We thus conclude that the S3-S4 linker is involved in the formation of the outer pore. Received: 3 May 1999 / Accepted: 8 July 1999 |
| |
Keywords: | : KST1 Mutagenesis Potassium channel Solanum Stomata Zn2+ |
本文献已被 SpringerLink 等数据库收录! |
|