Yanyong Kang, X. Edward Zhou, Xiang Gao, Yuanzheng He, Wei Liu, Andrii Ishchenko, Anton Barty, Thomas A. White, Oleksandr Yefanov, Gye Won Han, Qingping Xu, Parker W. de Waal, Jiyuan Ke, M. H. Eileen Tan, Chenghai Zhang, Arne Moeller, […] Karsten Melcher & H. Eric Xu
G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent pathways. Here we report the crystal structure of a constitutively active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin, determined by serial femtosecond X-ray laser crystallography. Together with extensive biochemical and mutagenesis data, the structure reveals an overall architecture of the rhodopsin–arrestin assembly in which rhodopsin uses distinct structural elements, including transmembrane helix 7 and helix 8, to recruit arrestin. Correspondingly, arrestin adopts the pre-activated conformation, with a ∼
20° rotation between the amino and carboxy domains, which opens up a cleft in arrestin to accommodate a short helix formed by the second intracellular loop of rhodopsin. This structure provides a basis for understanding GPCR-mediated arrestin-biased signalling and demonstrates the power of X-ray lasers for advancing the frontiers of structural biology.