Structural highlights
FunctionGNAI2_HUMAN Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems. The G(i) proteins are involved in hormonal regulation of adenylate cyclase: they inhibit the cyclase in response to beta-adrenergic stimuli. May play a role in cell division.[1] Isoform sGi2: Regulates the cell surface density of dopamine receptors DRD2 by sequestrating them as an intracellular pool.[2] Publication Abstract from PubMedThe class A adenosine A1 receptor (A1R) is a G-protein-coupled receptor that preferentially couples to inhibitory Gi/o heterotrimeric G proteins, has been implicated in numerous diseases, yet remains poorly targeted. Here we report the 3.6 A structure of the human A1R in complex with adenosine and heterotrimeric Gi2 protein determined by Volta phase plate cryo-electron microscopy. Compared to inactive A1R, there is contraction at the extracellular surface in the orthosteric binding site mediated via movement of transmembrane domains 1 and 2. At the intracellular surface, the G protein engages the A1R primarily via amino acids in the C terminus of the Galphai alpha5-helix, concomitant with a 10.5 A outward movement of the A1R transmembrane domain 6. Comparison with the agonist-bound beta2 adrenergic receptor-Gs-protein complex reveals distinct orientations for each G-protein subtype upon engagement with its receptor. This active A1R structure provides molecular insights into receptor and G-protein selectivity. Structure of the adenosine-bound human adenosine A1 receptor-Gi complex.,Draper-Joyce CJ, Khoshouei M, Thal DM, Liang YL, Nguyen ATN, Furness SGB, Venugopal H, Baltos JA, Plitzko JM, Danev R, Baumeister W, May LT, Wootten D, Sexton PM, Glukhova A, Christopoulos A Nature. 2018 Jun;558(7711):559-563. doi: 10.1038/s41586-018-0236-6. Epub 2018 Jun, 20. PMID:29925945[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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