G Protein-coupled Receptors

Abstract

The majority of transmembrane signal transduction in response to hormones and neurotransmitters is mediated by G protein-coupled receptors (GPCRs). 1 Moreover, GPCRs are the principal signal transducers for the senses of sight and smell. GPCRs are characterized by seven membrane-spanning domains with an extracellular N terminus and a cytoplasmic C terminus (Fig. 1) (GPCR structure reviewed in Refs.1-3). Based on certain key sequences, GPCRs can be divided into three major subfamilies, receptors related to rhodopsin (type A), receptors related to the calcitonin receptor (type B), and receptors related to the metabotropic receptors (type C).