Design, Synthesis and Pharmacological Evaluation of 5-Hydroxytryptamine<sub>1a</sub>Receptor Ligands to Explore the Three-Dimensional Structure of the Receptor
作者:Marı́a L. López-Rodrı́guez、Bruno Vicente、Xavier Deupi、Sergio Barrondo、Mireia Olivella、M. José Morcillo、Bellinda Behamú、Juan A. Ballesteros、Joan Sallés、Leonardo Pardo
DOI:10.1124/mol.62.1.15
日期:2002.7.1
In this work, we evaluate the structural differences of transmembrane helix 3 in rhodopsin and the 5-hydroxytryptamine 1A (5-HT1A) receptor caused by their different amino acid sequence. Molecular dynamics simulations of helix 3 in the 5-HT1A receptor tends to bend toward helix 5, in sharp contrast to helix 3 in rhodopsin, which is properly located within the position observed in the crystal structure. The relocation of the central helix 3 in the helical bundle facilitates the experimentally derived interactions between the neurotransmitters and the Asp residue in helix 3 and the Ser/Thr residues in helix 5. The different amino acid sequence that forms helix 3 in rhodopsin (basically the conserved Gly3.36Glu3.37 motif in the opsin family) and the 5-HT1A receptor (the conserved Cys3.36Thr3.37 motif in the neurotransmitter family) produces these structural divergences. These structural differences were experimentally checked by designing and testing ligands that contain comparable functional groups but at different interatomic distance. We have estimated the position of helix 3 relative to the other helices by systematically changing the distance between the functional groups of the ligands ( 1 and 2 ) that interact with the residues in the receptor. Thus, ligand 1 optimally interacts with a model of the 5-HT1A receptor that matches rhodopsin template, whereas ligand 2 optimally interacts with a model that possesses the proposed conformation of helix 3. The lack of affinity of 1 ( K i > 10,000 nM) and the high affinity of 2 ( K i = 24 nM) for the 5-HT1A receptor binding sites, provide experimental support to the proposed structural divergences of helix 3 between the 5-HT1A receptor and rhodopsin.
在这项研究中,我们评估了因氨基酸序列不同而导致的犀牛蛋白和5-羟色胺1A(5-HT1A)受体跨膜螺旋3的结构差异。分子动力学模拟显示,5-HT1A 受体中的螺旋 3 趋向于向螺旋 5 弯曲,这与斜视素中的螺旋 3 形成鲜明对比,后者正确地位于晶体结构中观察到的位置。螺旋 3 在螺旋束中的中心位置有利于神经递质与螺旋 3 中的 Asp 残基和螺旋 5 中的 Ser/Thr 残基之间的相互作用。形成螺旋 3 的氨基酸序列在犀牛蛋白(基本上是视蛋白家族中的 Gly3.36Glu3.37 保守基团)和 5-HT1A 受体(神经递质家族中的 Cys3.36Thr3.37 保守基团)中不同,从而产生了这些结构差异。通过设计和测试含有相似功能基团但原子间距离不同的配体,我们在实验中检验了这些结构差异。我们通过系统地改变与受体残基相互作用的配体(1 和 2)的功能基团之间的距离,估算出了螺旋 3 相对于其他螺旋的位置。因此,配体 1 与符合犀牛蛋白模板的 5-HT1A 受体模型的相互作用最佳,而配体 2 与具有拟议的螺旋 3 构象的模型的相互作用最佳。配体 1 与 5-HT1A 受体结合位点的亲和力不足(K i > 10,000 nM),而配体 2 与 5-HT1A 受体结合位点的亲和力较高(K i = 24 nM),这为 5-HT1A 受体和视网膜视蛋白之间的螺旋 3 结构差异提供了实验支持。