Molecular approximations between residues 21 and 23 of secretin and its receptor: Development of a model for peptide docking with the amino terminus of the secretin receptor
Molecular approximations between residues 21 and 23 of secretin and its receptor: Development of a model for peptide docking with the amino terminus of the secretin receptor
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DOI：
10.1124/mol.107.035402
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发表时间：
2007-08-01
影响因子：
3.6
通讯作者：
Miller, Laurence J.
中科院分区：
文献类型：
--
作者：
Dong, Maoqing;Lam, Polo C. -H.;Miller, Laurence J.
II类G蛋白偶联受体的结构独特的氨基末端结构域对于配体结合和受体激活至关重要。要了解它的确切作用，需要对其配体相互作用的分子基础和配体-受体复合体的构象有详细的了解。在这项工作中，我们使用了两个高亲和力，全激动剂，分泌素样光敏化探针，在第21和23位具有共价连接位点，并使用顺序蛋白分解和受体标记区域的测序来识别两个新的空间近似约束。位置21的探针标记受体残基Arg(15)，位置23的探针标记受体残基Arg(21)。利用促肾上腺皮质激素释放因子受体类似结构域的核磁共振结构，建立了促肾上腺皮质激素释放因子受体氨基末端结构域的同源模型。这与促分泌素受体跨膜束的同源模型相连，两个结构域基于肽骨架的连续性而彼此相对定位，并通过施加最近发现的氨基末端WDN序列与跨膜段6以上螺旋束区域之间的距离限制。促胰液素与这一模型的对接使用了在先前的光亲和标记研究中确定的七组空间近似约束。该模型被发现完全适应所有现有的约束，以及本工作中确定的两个新的近似。
The structurally unique amino-terminal domain of class II G protein-coupled receptors is critically important for ligand binding and receptor activation. Understanding the precise role it plays requires detailed insights into the molecular basis of its ligand interactions and the conformation of the ligand-receptor complex. In this work, we used two high-affinity, full-agonist, secretin-like photolabile probes having sites for covalent attachment in positions 21 and 23 and used sequential proteolysis and sequencing of the labeled region of the receptor to identify two new spatial approximation constraints. The position 21 probe labeled receptor residue Arg(15), whereas the position 23 probe labeled receptor residue Arg(21). A homology model of the amino-terminal domain of the secretin receptor was developed using the NMR structure of the analogous domain of the corticotropin-releasing factor receptor. This was attached to a homology model of the secretin receptor transmembrane bundle, with the two domains oriented relative to each other based on continuity of the peptide backbone and by imposing a distance restraint recently identified between the amino-terminal WDN sequence and the region of the helical bundle above transmembrane segment six. Secretin was docked to this model using seven sets of spatial approximation constraints identified in previous photoaffinity labeling studies. This model was found to fully accommodate all existing constraints, as well as the two new approximations identified in this work.