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Proc Natl Acad Sci U S A. 2007 Feb 6;104(6):2001-6. Epub 2007 Jan 30.

Structural basis for nucleotide exchange on G alpha i subunits and receptor coupling specificity.

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1
Department of Pharmacology and UNC Neuroscience Center, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7365, USA.

Abstract

Heterotrimeric G proteins are molecular switches that relay information intracellularly in response to various extracellular signals. How ligand-activated G protein-coupled receptors act at a distance to exert exchange activity on the Galpha nucleotide binding pocket is poorly understood. Here we describe the synergistic action of two peptides: one from the third intracellular loop of the D2 dopamine receptor (D2N), and a second, Galpha.GDP-binding peptide (KB-752) that mimics the proposed role of Gbetagamma in receptor-promoted nucleotide exchange. The structure of both peptides in complex with Galpha(i1) suggests that conformational changes in the beta3/alpha2 loop and beta6 strand act in concert for efficient nucleotide exchange. Two key residues in the alpha4 helix were found to define a receptor/Galpha(i) coupling specificity determinant.

PMID:
17264214
PMCID:
PMC1794300
DOI:
10.1073/pnas.0608599104
[Indexed for MEDLINE]
Free PMC Article
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