TY - JOUR T1 - 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 JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 78 LP - 87 DO - 10.1124/jpet.104.080424 VL - 313 IS - 1 AU - Evi Kostenis AU - Lene Martini AU - James Ellis AU - Maria Waldhoer AU - Arne Heydorn AU - Mette M. Rosenkilde AU - Pia K. Norregaard AU - Rasmus Jorgensen AU - Jennifer L. Whistler AU - Graeme Milligan Y1 - 2005/04/01 UR - http://jpet.aspetjournals.org/content/313/1/78.abstract N2 - 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 Gq-mediated signaling events compare 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. The American Society for Pharmacology and Experimental Therapeutics ER -