Mechanistic Understanding of the Palmitoylation of G Protein in the Allosteric Regulation of Adhesion Receptor GPR97.

Adhesion G-protein-coupled receptors (aGPCRs)-a major family of GPCRs-play critical roles in the regulation of tissue development and cancer progression. The orphan receptor GPR97, activated by glucocorticoid stress hormones, is a prototypical aGPCR. Although it has been established that the palmitoylation of the C-terminal G protein is essential for G's efficient engagement with the active GPR97, the detailed allosteric mechanism remains to be clarified. Hence, we performed extensive large-scale molecular dynamics (MD) simulations of the GPR97-G complex in the presence or absence of G palmitoylation. The conformational landscapes analyzed by Markov state models revealed that the overall conformation of GPR97 is preferred to be fully active when interacting with palmitoylated G protein. Structural and energetic analyses indicated that the palmitoylation of G can allosterically stabilize the critical residues in the ligand-binding pocket of GPR97 and increase the affinity of the ligand for GPR97. Furthermore, the community network analysis suggests that the palmitoylation of G not only allosterically strengthens the internal interactions between G and G, but also enhances the coupling between G and GPR97. Our study provides mechanistic insights into the regulation of aGPCRs via post-translational modifications of the G protein, and offers guidance for future drug design of aGPCRs.