Cryo-EM structures of Drosophila OR67d-Orco complexes reveal insect pheromone sensing mechanism

Pheromones mediate intraspecific communication to regulate the physiology and behavior of animals, particularly insects. The detection of pheromones is initiated by the binding of pheromone molecules, e.g., 11-cis-vaccenyl acetate (cVA) in Drosophila, to specific receptor proteins in chemosensory neurons, but the underlying molecular mechanisms remain unclear. Here, we report structures of Drosophila pheromone receptor OR67d-Orco complexes in apo closed, pheromone-bound open, and synthetic agonist VUAA1-bound open conformations. OR67d and Orco assemble into a hetero-tetrameric channel with a 1:3 stoichiometry. In OR67d, the inverted L-shaped cVA or its analog binds into a deep and bent hydrophobic pocket, inducing both local and global conformational changes that lead to an asymmetrical opening of the channel gate. By comparison, VUAA1 binds to Orco instead of OR67d to cause a similar asymmetrical opening. Together, our studies reveal the structural basis for pheromone activation of hetero-tetrameric pheromone receptors.