PerspectiveStructural Biology

Fine-tuning receptor–G protein activation and signaling

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Science  31 Jul 2020:
Vol. 369, Issue 6503, pp. 507-508
DOI: 10.1126/science.abc9291

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Summary

G protein–coupled receptors (GPCRs) are eukaryotic plasma membrane receptors that are organized into four classes in humans: A, B, C, and Frizzled. They internalize extracellular stimuli by activating a common pool of intracellular signaling partners such as the heterotrimeric G proteins (composed of Gα, β, and γ subunits) that subsequently induce an appropriate cellular response. Recent advances in cryo–electron microscopy (cryo-EM) enables challenging structures of GPCR signaling complexes to be solved, providing unprecedented insights about the molecular basis of their signal transduction (1). Qiao et al. (2) reported two cryo-EM structures of the class B human glucagon receptor (GCGR) Gs and Gi complexes, which helped clarify GCGR G protein selectivity. On page 523 of this issue, Hilger et al. (3) report a cryo-EM structure of a GCGR-Gs complex and reveal the effect of conformational changes on GCGR signaling properties. These studies support a common mechanism for class B receptor activation.

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