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Cryo-EM structure of the rhodopsin-Gαi-βγ complex reveals binding of the rhodopsin C-terminal tail to the Gβ subunit

By Ching-Ju Tsai, Jacopo Marino, Ricardo J Adaixo, Filip Pamula, Jonas Mühle, Shoji Maeda, Tilman Flock, Nicholas M. I. Taylor, Inayatulla Mohammed, Hugues Matile, Roger J. P. Dawson, Xavier Deupi, Henning Stahlberg, Gebhard F. X. Schertler

Posted 12 Feb 2019
bioRxiv DOI: 10.1101/547919 (published DOI: 10.7554/eLife.46041)

G protein-coupled receptors (GPCRs) are the largest class of integral membrane proteins and represent key targets for pharmacological research. GPCRs modulate cell physiology by engaging and activating a diversity of intracellular transducers, prominently heterotrimeric G proteins, but also G protein-receptor kinases (GRKs) and arrestins. The recent surge in the number of structures of GPCR-G protein complexes has expanded our understanding of G protein recognition and GPCR-mediated signal transduction. However, many aspects of these mechanisms, including the existence of transient interactions with transducers, have remained elusive. Here, we present the cryo-EM structure of the light-sensitive GPCR rhodopsin in complex with heterotrimeric Gi. In contrast to all reported structures, our density map reveals the receptor C-terminal tail bound to the Gβ subunit of the G protein heterotrimer. This observation provides a structural foundation for the role of the C-terminal tail in GPCR signaling, and of Gβ as scaffold for recruiting Gα subunits and GRKs. By comparing all available complex structures, we found a small set of common anchoring points that are G protein-subtype specific. Taken together, our structure and analysis provide new structural basis for the molecular events of the GPCR signaling pathway.

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