Booe Jason M, Walker Christopher S, Barwell James, Kuteyi Gabriel, Simms John, Jamaluddin Muhammad A, Warner Margaret L, Bill Roslyn M, Harris Paul W, Brimble Margaret A, Poyner David R, Hay Debbie L, Pioszak Augen A
Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
School of Biological Sciences and Maurice Wilkins Centre, University of Auckland, Auckland 1142, New Zealand.
Mol Cell. 2015 Jun 18;58(6):1040-52. doi: 10.1016/j.molcel.2015.04.018. Epub 2015 May 14.
Association of receptor activity-modifying proteins (RAMP1-3) with the G protein-coupled receptor (GPCR) calcitonin receptor-like receptor (CLR) enables selective recognition of the peptides calcitonin gene-related peptide (CGRP) and adrenomedullin (AM) that have diverse functions in the cardiovascular and lymphatic systems. How peptides selectively bind GPCR:RAMP complexes is unknown. We report crystal structures of CGRP analog-bound CLR:RAMP1 and AM-bound CLR:RAMP2 extracellular domain heterodimers at 2.5 and 1.8 Å resolutions, respectively. The peptides similarly occupy a shared binding site on CLR with conformations characterized by a β-turn structure near their C termini rather than the α-helical structure common to peptides that bind related GPCRs. The RAMPs augment the binding site with distinct contacts to the variable C-terminal peptide residues and elicit subtly different CLR conformations. The structures and accompanying pharmacology data reveal how a class of accessory membrane proteins modulate ligand binding of a GPCR and may inform drug development targeting CLR:RAMP complexes.
受体活性修饰蛋白（RAMP1 - 3）与G蛋白偶联受体（GPCR）降钙素受体样受体（CLR）相结合，能够选择性识别在心血管和淋巴系统中具有多种功能的肽类——降钙素基因相关肽（CGRP）和肾上腺髓质素（AM）。肽类如何选择性地结合GPCR:RAMP复合物尚不清楚。我们分别报告了分辨率为2.5 Å和1.8 Å的CGRP类似物结合的CLR:RAMP1细胞外结构域异二聚体以及AM结合的CLR:RAMP2细胞外结构域异二聚体的晶体结构。这些肽类类似地占据CLR上的一个共享结合位点，其构象的特征是在其C末端附近有一个β-转角结构，而不是与结合相关GPCR的肽类常见的α-螺旋结构。RAMP通过与可变的C末端肽残基形成不同的接触来扩大结合位点，并引发略有不同的CLR构象。这些结构和相关的药理学数据揭示了一类辅助膜蛋白如何调节GPCR的配体结合，并可能为靶向CLR:RAMP复合物的药物开发提供信息。
