Pang Y P, Cusack B, Groshan K, Richelson E
Neurochemistry and Neuropsychopharmacology Research, Mayo Foundation for Medical Education and Research, Jacksonville, Florida 32224, USA.
J Biol Chem. 1996 Jun 21;271(25):15060-8. doi: 10.1074/jbc.271.25.15060.
We report here the first proposed ligand binding site of the transmembrane receptor for neurotensin(8-13) in human and rat, the corresponding bound conformation of the peptide ligand, and site-directed mutagenesis studies that support the binding site model. These three-dimensional structures were generated by using a heuristic approach in conjunction with experimental data. The proposed neurotensin(8-13) binding site is primarily composed of eight residues (i.e., Phe326, Ile329, Trp334, Phe337, Tyr339, Phe341, Tyr342, and Tyr344 in the human receptor; Phe331, Ile334, Trp339, Phe342, Phe344, Phe346, Tyr347, and Tyr349 in the rat receptor) located in the third extracellular loop. The seven aromatic residues form an aromatic pocket on the extracellular surface of the neurotensin receptor to accommodate its ligands apparently by cation-pi, pi-pi, and hydrogen bonding interactions. The neurotensin(8-13) ligand adopts a compact conformation at the proposed binding site. In the bound conformation of neurotensin(8-13), the backbone of Arg9-Pro10-Tyr11-Ile12 forms the proline type I turn, and the hydroxy group of Tyr11 interacts with the two guanidinium groups of Arg8 and Arg9. These guanidinium groups are curled toward the hydroxy group so that they interact electrostatically with the hydroxy group, and that the guanidinium group of Arg9 forms an intra-hydrogen bond with the hydroxy group. The proposed three-dimensional structure may not only provide a basis for rationalizing mutations of the neurotensin receptor gene but also offer insights into understanding the binding of many neurotensin analogs, biological functions of the neurotensin receptors, and structural elements for species specificity of the neurotensin receptors, and may expedite developing nonpeptidic neurotensin mimetics for the potential treatment of the neuropsychiatric diseases.
我们在此报告人源和大鼠源神经降压素（8 - 13）跨膜受体首个提出的配体结合位点、肽配体相应的结合构象以及支持该结合位点模型的定点诱变研究。这些三维结构是通过结合实验数据的启发式方法生成的。所提出的神经降压素（8 - 13）结合位点主要由位于第三个细胞外环的八个残基组成（即人源受体中的Phe326、Ile329、Trp334、Phe337、Tyr339、Phe341、Tyr342和Tyr344；大鼠源受体中的Phe331、Ile334、Trp339、Phe342、Phe344、Phe346、Tyr347和Tyr349）。这七个芳香族残基在神经降压素受体的细胞外表面形成一个芳香口袋，显然通过阳离子 - π、π - π和氢键相互作用来容纳其配体。神经降压素（8 - 13）配体在所提出的结合位点采取紧密构象。在神经降压素（8 - 13）的结合构象中，Arg9 - Pro10 - Tyr11 - Ile12的主链形成I型脯氨酸转角，Tyr11的羟基与Arg8和Arg9的两个胍基相互作用。这些胍基向羟基卷曲，以便它们与羟基发生静电相互作用，并且Arg9的胍基与羟基形成分子内氢键。所提出的三维结构不仅可为解释神经降压素受体基因的突变提供基础，还可为理解许多神经降压素类似物的结合、神经降压素受体的生物学功能以及神经降压素受体物种特异性的结构元件提供见解，并且可能加速开发用于潜在治疗神经精神疾病的非肽类神经降压素模拟物。
