Leiden/Amsterdam Center for Drug Research, Department of Medicinal Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081HV Amsterdam, the Netherlands.
Mol Pharmacol. 2011 Feb;79(2):262-9. doi: 10.1124/mol.110.066068. Epub 2010 Nov 16.
Rearrangement of transmembrane domains (TMs) 3 and 5 after agonist binding is necessary for stabilization of the active state of class A G protein-coupled receptors (GPCRs). Using site-directed mutagenesis and functional assays, we provide the first evidence that the TAS(I/V) sequence motif at positions 3.37 to 3.40, highly conserved in aminergic receptors, plays a key role in the activation of the histamine H₁ receptor. By combining these data with structural information from X-ray crystallography and computational modeling, we suggest that Thr(3.37) interacts with TM5, stabilizing the inactive state of the receptor, whereas the hydrophobic side chain at position 3.40, highly conserved in the whole class A GPCR family, facilitates the reorientation of TM5. We propose that the structural change of TM5 during the process of GPCR activation involves a local Pro(5.50)-induced unwinding of the helix, acting as a hinge, and the highly conserved hydrophobic Ile(3.40) side chain, acting as a pivot.
激动剂结合后跨膜结构域 (TMs) 3 和 5 的重排对于稳定 A 类 G 蛋白偶联受体 (GPCR) 的活性状态是必要的。通过定点突变和功能测定，我们首次提供证据表明，在胺能受体中高度保守的位置 3.37 到 3.40 的 TAS(I/V)序列基序在组胺 H₁受体的激活中发挥关键作用。将这些数据与来自 X 射线晶体学和计算建模的结构信息相结合，我们提出 Thr(3.37)与 TM5 相互作用，稳定受体的非活性状态，而位置 3.40 处高度保守的疏水性侧链在整个 A 类 GPCR 家族中，有利于 TM5 的重新定向。我们提出，GPCR 激活过程中 TM5 的结构变化涉及局部 Pro(5.50)诱导的螺旋展开，充当铰链，以及高度保守的疏水性 Ile(3.40)侧链，充当枢轴。
