Allosteric functioning of dimeric class C G-protein-coupled receptors

Whereas most membrane receptors are oligomeric entities, G-protein-coupled receptors have long been thought to function as monomers. Within the last 15 years, accumulating data have indicated that G-protein-coupled receptors can form dimers or even higher ordered oligomers, but the general functional significance of this phenomena is not yet clear. Among the large G-protein-coupled receptor family, class C receptors represent a well-recognized example of constitutive dimers, both subunits being linked, in most cases, by a disulfide bridge. In this review article, we show that class C G-protein-coupled receptors are multidomain proteins and highlight the importance of their dimerization for activation. We illustrate several consequences of this in terms of specific functional properties and drug development.