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Publication Abstract from PubMed

Many neurotransmitter receptors activate G proteins through exchange of GDP for GTP. The intermediate nucleotide-free state has eluded characterization, due largely to its inherent instability. Here we characterize a G protein variant associated with a rare neurological disorder in humans. Galpha(o)(K46E) has a charge reversal that clashes with the phosphate groups of GDP and GTP. As anticipated, the purified protein binds poorly to guanine nucleotides yet retains wild-type affinity for G protein betagamma subunits. In cells with physiological concentrations of nucleotide, Galpha(o)(K46E) forms a stable complex with receptors and Gbetagamma, impeding effector activation. Further, we demonstrate that the mutant can be easily purified in complex with dopamine-bound D2 receptors, and use cryo-electron microscopy to determine the structure, including both domains of Galpha(o), without nucleotide or stabilizing nanobodies. These findings reveal the molecular basis for the first committed step of G protein activation, establish a mechanistic basis for a neurological disorder, provide a simplified strategy to determine receptor-G protein structures, and a method to detect high affinity agonist binding in cells.

A neurodevelopmental disorder mutation locks G proteins in the transitory pre-activated state.,Knight KM, Krumm BE, Kapolka NJ, Ludlam WG, Cui M, Mani S, Prytkova I, Obarow EG, Lefevre TJ, Wei W, Ma N, Huang XP, Fay JF, Vaidehi N, Smrcka AV, Slesinger PA, Logothetis DE, Martemyanov KA, Roth BL, Dohlman HG Nat Commun. 2024 Aug 5;15(1):6643. doi: 10.1038/s41467-024-50964-z. PMID:39103320^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.