Evolution of odorant receptors

Odorant receptors (ORs) located in the nasal epithelium, at the ciliated su rface of olfactory sensory neurons, represent the initial step of a transdu ction cascade that leads to odor detection. ORs form the largest and most d iverse family of G-protein-coupled receptors (GPCRs). They are encoded by a multigene family that has been partially characterized in cyclostomes, tel eosts, amphibia, birds and mammals, as well as in Drosophila melanogaster a nd the nematode Caenorhabditis elegans. As new sequence data emerge, it is increasingly clear that OR primary structure can vary dramatically across p hyla. Some chemoreceptors are encoded by genes with little sequence similar ity to the prototypical ORs originally isolated in mammals. A large number of sequences are now available allowing a detailed study of the evolutionar y implications of OR diversity across species. This review discusses the ev olutionary implications of the divergent primary structures of chemorecepto rs with identical functions. BioEssays 22:803-810, 2000. (C) 2000 John Wile y & Sons, Inc.