Evolution of class A G-protein-coupled receptors: implications for molecular modeling.

Class A or rhodopsin-like G-protein-coupled receptors (GPCRs) constitute the largest transmembrane receptor family of the human genome. Because of their biological and pharmaceutical importance, the evolutionary history of these receptors has been widely studied. Most studies agree on the classification of the 700 members of this family into a dozen of sub-families. However, the relationship between these sub-families remains controversial and the molecular processes that drove the evolution and diversification of such a large family have still to be determined. We review here the evolutionary analyses carried out on class A GPCRs either by phylogenetic methods or by multidimensional scaling (MDS). We detail the key molecular events driving the evolution of this receptor family. We analyze these events in view of the recently resolved crystal structures of GPCRs and we discuss the usefulness of evolutionary information to help molecular modeling.