The mid-region of parathyroid hormone (1-34) serves as a functional docking domain in receptor activation.
The mid-region of parathyroid hormone (1-34) serves as a functional docking domain in receptor activation.
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DOI：
10.1021/bi051833a
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发表时间：
2006-01
期刊：
影响因子：
2.9
通讯作者：
A. Wittelsberger;M. Corich;B. Thomas;Byung-Kwon Lee;A. Barazza;P. Czodrowski;D. Mierke;M. Chorev;M. Rosenblatt
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文献类型：
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作者：
A. Wittelsberger;M. Corich;B. Thomas;Byung-Kwon Lee;A. Barazza;P. Czodrowski;D. Mierke;M. Chorev;M. Rosenblatt
阐明甲状旁腺激素（PTH）和它的同源G蛋白偶联受体（PTHR 1）之间的双分子界面应该产生的分子识别的基础和配体介导的细胞内信号传导的机制的系统，这是至关重要的调节血液中的钙水平的见解。我们使用光亲和扫描（PAS）来确定PTH-（1-34）非结构化中间区域结构域残基的关键配体-受体相互作用。发现在11、15、18或21位含有单个光反应性对苯甲酰苯丙氨酸（Bpa）残基的四种PTH类似物分别在受体区域内发生光交联[165-176]、[183-189]、[190-298]和[165-176]。除了这些中间区域的接触作为限制，我们以前提出的模型的PTH-PTHR 1复合物和广泛的分子模拟实验，使大量的改进模型。具体而言，（1）激素的整体受体结合构象不是延伸的，而是弯曲的;（2）受体N-末端胞外结构域（N-ECD）的螺旋[169-176]被重定向到七螺旋束;（3）激素在跨膜（TM）螺旋1和2的顶部之间，而不是在TM-7和TM-1之间穿过。这显著改变了激素的受体结合的三级结构和N-ECD的C-末端的拓扑取向的模型在受体双分子复合物。我们提出，PTH-（1-34）的中间区域具有固定的作用，通过与受体的广泛接触，激素的N-末端螺旋进入TM-1和TM-2之间的七螺旋束。这种锚定将氨基末端定向到激活受体的位置。
Elucidating the bimolecular interface between parathyroid hormone (PTH) and its cognate G protein-coupled receptor (PTHR1) should yield insights into the basis of molecular recognition and the mechanism of ligand-mediated intracellular signaling for a system that is critically important in regulating calcium levels in blood. We used photoaffinity scanning (PAS) to identify key ligand-receptor interactions for residues from the unstructured mid-region domain of PTH-(1-34). Four PTH analogues, containing a single photoreactive p-benzoylphenylalanine (Bpa) residue in position 11, 15, 18, or 21, were found to photo-cross-link within receptor regions [165-176], [183-189], [190-298], and [165-176], respectively. Addition of these mid-region contacts as constraints to our previously proposed model of the PTH-PTHR1 complex and extensive molecular simulation experiments enables substantial refinement of the model. Specifically, (1) the overall receptor-bound conformation of the hormone is not extended, but bent; (2) helix [169-176] of the N-terminal extracellular domain (N-ECD) of the receptor is redirected toward the heptahelical bundle; and (3) the hormone traverses between the top of transmembrane (TM) helices 1 and 2, rather than between TM-7 and TM-1. This significantly alters the model of both the receptor-bound tertiary structure of the hormone and the topological orientation of the C-terminus of the N-ECD in the hormone-receptor bimolecular complex. We propose that the mid-region of PTH-(1-34) has a role in fixing, by extensive contacts with the receptor, the entry of the N-terminal helix of the hormone into the heptahelical bundle between TM-1 and TM-2. This anchorage would orient the amino terminus into position to activate the receptor.