The dance of the clams:: twists and turns in the family C GPCR homodimer

The recently published high-resolution crystal structures of the amino-terminal domains (ATDs) of the metabotropic glutamate 1 (mglu(1)) receptor homodimer present an exciting milestone in the study of the molecular pharmacology of family C G-protein-coupled receptors (GPCRs). In this article, we outline recent developments in the understanding of signal transduction by family C GPCR homodimers, with particular emphasis on the conformational movements of the two ATDs, in addition to allosteric modulation and competitive and noncompetitive antagonism of these processes.