TY - JOUR TI - Structural insight into the activation of a class B G-protein-coupled receptor by peptide hormones in live human cells AU - Seidel, Lisa AU - Zarzycka, Barbara AU - Zaidi, Saheem A AU - Katritch, Vsevolod AU - Coin, Irene A2 - Shan, Yibing VL - 6 PY - 2017 DA - 2017/08/03 SP - e27711 C1 - eLife 2017;6:e27711 DO - 10.7554/eLife.27711 UR - https://doi.org/10.7554/eLife.27711 AB - The activation mechanism of class B G-protein-coupled receptors (GPCRs) remains largely unknown. To characterize conformational changes induced by peptide hormones, we investigated interactions of the class B corticotropin-releasing factor receptor type 1 (CRF1R) with two peptide agonists and three peptide antagonists obtained by N-truncation of the agonists. Surface mapping with genetically encoded photo-crosslinkers and pair-wise crosslinking revealed distinct footprints of agonists and antagonists on the transmembrane domain (TMD) of CRF1R and identified numerous ligand-receptor contact sites, directly from the intact receptor in live human cells. The data enabled generating atomistic models of CRF- and CRF(12-41)-bound CRF1R, further explored by molecular dynamics simulations. We show that bound agonist and antagonist adopt different folds and stabilize distinct TMD conformations, which involves bending of helices VI and VII around flexible glycine hinges. Conservation of these glycine hinges among all class B GPCRs suggests their general role in activation of these receptors. KW - class B GPCRs KW - expanded genetic code KW - bioorthogonal crosslinking KW - molecular modeling KW - orthosteric antagonism KW - peptide ligands JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -