Fig. 3: Conformational diversity of the VFT domains upon glutamate binding.

A Activation FEL of VFTs onto the COM of LB2s and Cα RMSD from the conformation of the mGlu5 VFTs crystal structure in complex with glutamate (PDB ID:3LMK). The free energy scales of the landscape are shown on the right and are expressed in kcal/mol. B Per-protomer analysis of the S2 metastable state uncovered an alternative configuration of the VFTs, termed S2’. C Elevated view of the helix B-C interface from S1 to S3 states. The crucial hydrophobic residues are presented in stick mode. D Front view of the helix B-C interface from S1 to S3 states. Both helix B and helix C are highlighted. The helix C cross angle, reflecting the releasement of the hydrophobic constraint of the helix B-C interface, is also labeled. The values are 155.4° and 93.1° in the resting and active cryo-EM structures, respectively. E A top view of the helix B-C interface from S1 to S3 states. The helix B is depicted as a cartoon, with key residues shown in stick mode. The crucial polar interactions are represented by yellow dashed lines. F Schematic illustration of the activation pathway of VFTs in terms of intra-protomer (open ‘o’ to close ‘c’) and inter-protomer (relaxed ‘R’ to activate ‘A’) conformational transitions. Upon agonist binding, the co-existence of transient Rco (S2) and Rcc (S2’) intermediate conformations was identified between the Roo and Acc conformations.