Wick M J, Mihic S J, Ueno S, Mascia M P, Trudell J R, Brozowski S J, Ye Q, Harrison N L, Harris R A
Department of Pharmacology, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Proc Natl Acad Sci U S A. 1998 May 26;95(11):6504-9. doi: 10.1073/pnas.95.11.6504.
Alcohols in the homologous series of n-alcohols increase in central nervous system depressant potency with increasing chain length until a "cutoff" is reached, after which further increases in molecular size no longer increase alcohol potency. A similar phenomenon has been observed in the regulation of ligand-gated ion channels by alcohols. Different ligand-gated ion channels exhibit radically different cutoff points, suggesting the existence of discrete alcohol binding pockets of variable size on these membrane proteins. The identification of amino acid residues that determine the alcohol cutoff may, therefore, provide information about the location of alcohol binding sites. Alcohol regulation of the glycine receptor is critically dependent on specific amino acid residues in transmembrane domains 2 and 3 of the alpha subunit. We now demonstrate that these residues in the glycine alpha1 and the gamma-aminobutyric acid rho1 receptors also control alcohol cutoff. By mutation of Ser-267 to Gln, it was possible to decrease the cutoff in the glycine alpha1 receptor, whereas mutation of Ile-307 and/or Trp-328 in the gamma-aminobutyric acid rho1 receptor to smaller residues increased the cutoff. These results support the existence of alcohol binding pockets in these membrane proteins and suggest that the amino acid residues present at these positions can control the size of the alcohol binding cavity.
正构醇同系物中的醇类,其链长增加时,对中枢神经系统的抑制效力也会增强,直至达到一个“截止点”,此后分子大小进一步增加并不会再提高醇类的效力。在醇类对配体门控离子通道的调节中也观察到了类似现象。不同的配体门控离子通道表现出截然不同的截止点,这表明这些膜蛋白上存在大小可变的离散醇类结合口袋。因此,确定决定醇类截止点的氨基酸残基,可能会提供有关醇类结合位点位置的信息。甘氨酸受体的醇类调节关键取决于α亚基跨膜结构域2和3中的特定氨基酸残基。我们现在证明,甘氨酸α1受体和γ-氨基丁酸ρ1受体中的这些残基也控制着醇类截止点。通过将甘氨酸α1受体中的Ser-267突变为Gln,可以降低截止点,而将γ-氨基丁酸ρ1受体中的Ile-307和/或Trp-328突变为较小的残基则会增加截止点。这些结果支持了这些膜蛋白中存在醇类结合口袋,并表明这些位置上的氨基酸残基可以控制醇类结合腔的大小。