A highly conserved glycine within linker I and the extreme C terminus of G protein α subunits interact cooperatively in switching G protein-coupled receptor-to-effector specificity

Evi Kostenis, Lene Martini, James Ellis, Maria Waldhoer, Arne Heydorn, Mette M. Rosenkilde, Pia K. Norregaard, Rasmus Jorgensen, Jennifer Whistler, Graeme Milligan

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Numerous studies have attested to the importance of the extreme C terminus of G protein α subunits in determining their selectivity of receptor recognition. We have previously reported that a highly conserved glycine residue within linker I is important for constraining the fidelity of receptor recognition by Gαq proteins. Herein, we explored whether both modules (linker I and extreme C terminus) interact cooperatively in switching G protein-coupled receptor (GPCR)-to-effector specificity and created as models mutant Gαq proteins in which glycine was replaced with various amino acids and the C-terminal five Gαq residues with the corresponding Gαi or Gαs sequence. Coupling properties of the mutated Gαq proteins were determined after coexpression with a panel of 13 Gi-and Gs-selective receptors and compared with those of Gα proteins modified in only one module. Gα proteins modified in both modules are significantly more efficacious in channeling non-Gq-selective receptors to G q-mediated signaling events compared with those containing each module alone. Additive effects of both modules were observed even if individual modules lacked an effect on GPCR-to-effector specificity. Dually modified Gα proteins were also superior in conferring high-affinity agonist sites onto a coexpressed GPCR in the absence, but not in the presence, of guanine nucleotides. Together, our data suggest that receptor-G protein coupling selectivity involves cooperative interactions between the extreme C terminus and linker I of Gα proteins and that distinct determinants of selectivity exist for individual receptors.

Original languageEnglish (US)
Pages (from-to)78-87
Number of pages10
JournalJournal of Pharmacology and Experimental Therapeutics
Issue number1
StatePublished - Apr 1 2005
Externally publishedYes


ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

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