Xiu Xinan, Hanek Ariele P, Wang Jinti, Lester Henry A, Dougherty Dennis A
Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
J Biol Chem. 2005 Dec 16;280(50):41655-66. doi: 10.1074/jbc.M508635200. Epub 2005 Oct 10.
In the Cys loop superfamily of ligand-gated ion channels, a global conformational change, initiated by agonist binding, results in channel opening and the passage of ions across the cell membrane. The detailed mechanism of channel gating is a subject that has lent itself to both structural and electrophysiological studies. Here we defined a gating interface that incorporates elements from the ligand binding domain and transmembrane domain previously reported as integral to proper channel gating. An overall analysis of charged residues within the gating interface across the entire superfamily showed a conserved charging pattern, although no specific interacting ion pairs were conserved. We utilized a combination of conventional mutagenesis and the high precision methodology of unnatural amino acid incorporation to study extensively the gating interface of the mouse muscle nicotinic acetylcholine receptor. We found that charge reversal, charge neutralization, and charge introduction at the gating interface are often well tolerated. Furthermore, based on our data and a reexamination of previously reported data on gamma-aminobutyric acid, type A, and glycine receptors, we concluded that the overall charging pattern of the gating interface, and not any specific pairwise electrostatic interactions, controls the gating process in the Cys loop superfamily.
在配体门控离子通道的半胱氨酸环超家族中，由激动剂结合引发的整体构象变化会导致通道开放以及离子穿过细胞膜。通道门控的详细机制是一个适合进行结构和电生理研究的课题。在这里，我们定义了一个门控界面，该界面整合了先前报道的对适当通道门控至关重要的配体结合结构域和跨膜结构域的元件。对整个超家族门控界面内带电残基的全面分析显示出一种保守的电荷模式，尽管没有特定的相互作用离子对是保守的。我们结合使用传统诱变和非天然氨基酸掺入的高精度方法，广泛研究了小鼠肌肉烟碱型乙酰胆碱受体的门控界面。我们发现，门控界面处的电荷反转、电荷中和和电荷引入通常具有良好的耐受性。此外，基于我们的数据以及对先前报道的关于A型γ-氨基丁酸和甘氨酸受体的数据的重新审视，我们得出结论，门控界面的整体电荷模式而非任何特定的成对静电相互作用控制着半胱氨酸环超家族中的门控过程。
