Crystal structure of the light-activated constitutively active N2C, M257Y,D282C rhodopsin mutant in complex with a peptide resembling the C-terminus of the Galpha-protein subunit (GaCT)
G protein-coupled receptors (GPCR) are seven transmembrane helix proteins that couple binding of extracellular ligands to conformational changes and activation of intracellular G proteins, GPCR kinases, and arrestins. Constitutively active mutants are ubiquitously found among GPCRs and increase the inherent basal activity of the receptor, which often correlates with a pathological outcome ...
G protein-coupled receptors (GPCR) are seven transmembrane helix proteins that couple binding of extracellular ligands to conformational changes and activation of intracellular G proteins, GPCR kinases, and arrestins. Constitutively active mutants are ubiquitously found among GPCRs and increase the inherent basal activity of the receptor, which often correlates with a pathological outcome. Here, we have used the M257Y(6.40) constitutively active mutant of the photoreceptor rhodopsin in combination with the specific binding of a C-terminal fragment from the G protein alpha subunit (GαCT) to trap a light activated state for crystallization. The structure of the M257Y/GαCT complex contains the agonist all-trans-retinal covalently bound to the native binding pocket and resembles the G protein binding metarhodopsin-II conformation obtained by the natural activation mechanism; i.e., illumination of the prebound chromophore 11-cis-retinal. The structure further suggests a molecular basis for the constitutive activity of 6.40 substitutions and the strong effect of the introduced tyrosine based on specific interactions with Y223(5.58) in helix 5, Y306(7.53) of the NPxxY motif and R135(3.50) of the E(D)RY motif, highly conserved residues of the G protein binding site.
Related Citations:
Crystal Structure of a Thermally Stable Rhodopsin Mutant. Standfuss, J., Xie, G., Edwards, P.C., Burghammer, M., Oprian, D.D., Schertler, G.F.X. (2007) J Mol Biol 372: 1179
The Structural Basis of Agonist-Induced Activation in Constitutively Active Rhodopsin. Standfuss, J., Edwards, P.C., D'Antona, A., Fransen, M., Xie, G., Oprian, D.D., Schertler, G.F.X. (2011) Nature 471: 656
Organizational Affiliation:
Paul Scherrer Institut, Villigen PSI, 5232, Switzerland.
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