Fig. 8.

Activation of Gi protein mediated by δOR favourably proceeds with both ligand-first and G protein-first activation mechanisms. (A,E) Our minimised structures of human κOR-MP1104 and human δOR-DPI-287, respectively, in the absence of Gi protein. MetaMD free energy of (B) the interaction between R156^3.50 (NH2)-T273^6.34(OG1) and (C) the interaction between R156^3.50 (NE)-T273^6.34(OG1). (D) Comparison of the minimised human κOR-MP1104 (pink) with the crystallographic inactive conformation of human κOR (green) resolved by crystallography (Wu et al., 2012). MetaMD free energy of (F) the interaction between R146^3.50(NH1)-T260^6.34(OG1), (G) the interaction between R146^3.50 (NH2)-T273^6.34(OG1) and (H) the interaction between R146^3.50 (NE)-T273^6.34(OG1). (I) Comparison of the minimised human δOR-DPI-287 (pink) with the crystallographic inactive conformation of human δOR (green) resolved by crystallography (Fenalti et al., 2014). All RMSDs were calculated for the Cα atoms on the TM domains. Variation of the free energy difference with time was monitored to evaluate the convergence of metaMD simulations. The weighted averages and the standard deviations were calculated for the converged period between the initial configuration before metaMD ‘i’ and the final conformation ‘f’ after metaMD calculations (Supplementary Fig. S10).