Functional expression and characterization of a Drosophila odorant receptor in a heterologous cell system

Odorant receptors (ORs) constitute the molecular basis for the detection of volatile odorous molecules and the perception of smell. Our understanding of chemical senses has been greatly expanded by the discovery of the OR gen e families in vertebrates and in the nematode Caenorhabditis elegans. Recen tly, candidate Drosophila OR genes have been identified. The putative ORs d o not possess any primary sequence identity with known vertebrate or C. ele gans receptors, but belong to the family of G protein-coupled receptors acc ording to their predicted seven transmembrane topology. To prove olfactory function of these proteins, we expressed a member of the putative Drosophil a OR gene family, Or43a, in Xenopus laevis oocytes. Using two-electrode vol tage-damp recording we identified four odors (cyclohexanone, cyclohexanol, benzaldehyde, and benzyl alcohol) that activated the receptor at low microm olar concentration and structurally related substances that did not. This r eport shows the function and specificity of a member of the recently identi fied family of Drosophila ORs expressed in a heterologous system.