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From Proteopedia
Structure of the Rhodopsin-Transducin-Nanobody Complex
Structural highlights
Function[GNAT1_BOVIN] Guanine nucleotide-binding proteins (G proteins) are involved as modulators or transducers in various transmembrane signaling systems. Transducin is an amplifier and one of the transducers of a visual impulse that performs the coupling between rhodopsin and cGMP-phosphodiesterase. [GBB1_BOVIN] Guanine nucleotide-binding proteins (G proteins) are involved as a modulator or transducer in various transmembrane signaling systems. The beta and gamma chains are required for the GTPase activity, for replacement of GDP by GTP, and for G protein-effector interaction. [OPSD_BOVIN] Photoreceptor required for image-forming vision at low light intensity. Required for photoreceptor cell viability after birth. Light-induced isomerization of 11-cis to all-trans retinal triggers a conformational change leading to G-protein activation and release of all-trans retinal (By similarity).[1] [2] Publication Abstract from PubMedRhodopsin (Rho), a prototypical G-protein-coupled receptor (GPCR) in vertebrate vision, activates the G-protein transducin (GT) by catalyzing GDP-GTP exchange on its alpha subunit (GalphaT). To elucidate the determinants of GT coupling and activation, we obtained cryo-EM structures of a fully functional, light-activated Rho-GT complex in the presence and absence of a G-protein-stabilizing nanobody. The structures illustrate how GT overcomes its low basal activity by engaging activated Rho in a conformation distinct from other GPCR-G-protein complexes. Moreover, the nanobody-free structures reveal native conformations of G-protein components and capture three distinct conformers showing the GalphaT helical domain (alphaHD) contacting the Gbetagamma subunits. These findings uncover the molecular underpinnings of G-protein activation by visual rhodopsin and shed new light on the role played by Gbetagamma during receptor-catalyzed nucleotide exchange. Structures of the Rhodopsin-Transducin Complex: Insights into G-Protein Activation.,Gao Y, Hu H, Ramachandran S, Erickson JW, Cerione RA, Skiniotis G Mol Cell. 2019 Jun 24. pii: S1097-2765(19)30440-X. doi:, 10.1016/j.molcel.2019.06.007. PMID:31300275[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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