Fig. 5. Graphical illustration of family C GPCR structure.⁴¹ Reprinted with permission from Springer Nature: Springer Nature, Acta Pharmacologica Sinica, Structure and ligand recognition of class C GPCRs, L. Chun, W.-h. Zhang and J.-f. Liu (2012). (A) Represents the structural organisation of family C GPCRs. Family C GPCRs have a peculiar structure which comprises of VFT with two lobes separated by an orthosteric binding pocket, a CRD and a TMD except for GABA_B receptor. (B) Graphical illustration of two members family C GPCRs; GABA_B receptor (heterodimer) and mGlu receptor (homodimer). There is a direct link between VFT and TMD in the GABA_B receptors and the two subunits, GABA_B1 and GABA_B2 make an obligatory heterodimer while the VFT connects to TMD using CRD in the mGlu receptors. The mGlu receptors form homodimers which can potentially offer two other orthosteric binding pocket per dimer.⁴¹.