Molecular modeling and mutagenesis reveals a tetradentate binding site for Zn2+ in GABA(A) alphabeta receptors and provides a structural basis for the modulating effect of the gamma subunit.
Molecular modeling and mutagenesis reveals a tetradentate binding site for Zn2+ in GABA(A) alphabeta receptors and provides a structural basis for the modulating effect of the gamma subunit.
复制标题
分子建模和诱变揭示了 GABA(A) Alphata 受体中 Zn2 的四齿结合位点，并为 γ 亚基的调节作用提供了结构基础。
DOI：
10.1021/ci700324a
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发表时间：
2008
影响因子：
5.6
通讯作者：
Harrison,NeilL
中科院分区：
文献类型：
--
作者：
Trudell,JamesR;Yue,MinervaE;Bertaccini,EdwardJ;Jenkins,Andrew;Harrison,NeilL
Gamma-aminobutyric acid type A receptors (GABAA-R) containing α1β2γ2 subunits are weakly inhibited by Zn2+, whereas receptors containing only the α1β2 subunits are strongly inhibited. We built homology models of the ion pores of α1β2 and α1β2γ2 GABAA-R using coordinates of the nicotinic acetylcholine receptor as a template. Threading the GABAA-R β2 sequence onto this template placed the 17‘ histidine and the 20‘ glutamate residues at adjacent locations in the mouth of the pore, such that a nearly ideal tetradentate site for Zn2+was formed from two histidine and two glutamate residues between adjacent β subunits in the α1β2 GABAA-R. Following optimization with CHARMM, the distance between the α-carbons of the adjacent histidine residues was approximately 9.2 Å, close to the ideal distance for a Zn2+binding site. Loss of inhibition by Zn2+in α1β2γ2 GABAA-R can be explained by the geometry of these residues in the arrangement α1β2γ2α1β2, in which the nearest C-α-C-α distance between the histidine residues is 15.5 Å, too far apart for an energetically optimal Zn2+binding site. We then mutated the γ subunit at the 17‘ and/or 20‘ positions. Zn2+inhibition was not restored in α1β2γ2 (I282H) receptors. A novel finding is that the modeling shows the native 20‘ lysine in γ2 can compete with Zn2+for binding to the inserted 17‘ histidine. Sensitivity to Zn2+was restored in the double mutant receptor, α1β2γ2 (I282H; K285E), in which the competition with lysine was removed and a more favorable Zn2+binding site was formed.
