Structural basis for odorant recognition of the insect odorant receptor OR-Orco heterocomplex

Insects detect and discriminate a diverse array of chemicals using odorant receptors (ORs), which are ligand-gated ion channels comprising a divergent odorant-sensing OR and a conserved odorant receptor co-receptor (Orco). In this work, we report structures of the Ap OR5-Orco heterocomplex from the pea aphid Acyrthosiphon pisum alone and bound to its known activating ligand, geranyl acetate. In these structures, three Ap Orco subunits serve as scaffold components that cannot bind the ligand and remain relatively unchanged. Upon ligand binding, the pore-forming helix S7b of Ap OR5 shifts outward from the central pore axis, causing an asymmetrical pore opening for ion influx. Our study provides insights into…