Structural Elements in the G?s and G?q C Termini That Mediate Selective G Protein-coupled Receptor (GPCR) Signaling.

ABSTRACT: Although the importance of the C terminus of the ? subunit of the heterotrimeric G protein in G protein-coupled receptor (GPCR)-G protein pairing is well established, the structural basis of selective interactions remains unknown. Here, we combine live cell FRET-based measurements and molecular dynamics simulations of the interaction between the GPCR and a peptide derived from the C terminus of the G? subunit (G? peptide) to dissect the molecular mechanisms of G protein selectivity. We observe a direct link between G? peptide binding and stabilization of the GPCR conformational ensemble. We find that cognate and non-cognate G? peptides show deep and shallow binding, respectively, and in distinct orientations within the GPCR. Binding of the cognate G? peptide stabilizes the agonist-bound GPCR conformational ensemble resulting in favorable binding energy and lower flexibility of the agonist-GPCR pair. We identify three hot spot residues (G?s/G?q-Gln-384/Leu-349, Gln-390/Glu-355, and Glu-392/Asn-357) that contribute to selective interactions between the ?2-adrenergic receptor (?2-AR)-G?s and V1A receptor (V1AR)-G?q The G?s and G?q peptides adopt different orientations in ?2-AR and V1AR, respectively. The ?2-AR/G?s peptide interface is dominated by electrostatic interactions, whereas the V1AR/G?q peptide interactions are predominantly hydrophobic. Interestingly, our study reveals a role for both favorable and unfavorable interactions in G protein selection. Residue Glu-355 in G?q prevents this peptide from interacting strongly with ?2-AR. Mutagenesis to the G?s counterpart (E355Q) imparts a cognate-like interaction. Overall, our study highlights the synergy in molecular dynamics and FRET-based approaches to dissect the structural basis of selective G protein interactions.

SUBMITTER: Semack A 

PROVIDER: S-EPMC5016181 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature