Odorant coreceptor which complexes with conventional odorant receptors (ORs) to form odorant-sensing units, providing sensitive and prolonged odorant signaling and calcium permeability. Orco is a universal and integral part of the functional odorant receptor, involved in the dendritic localization of other olfactory receptors. Expression of Orco alone leads to formation of rapid and transient ion channels not directly responding to odorants, but directly activated by intracellular cAMP or cGMP. Snmp, Or67d and lush act in concert to capture fatty-acid-derived male pheromone 11-cis vaccenyl acetate (cVA) molecules on the surface of Or67d expressing olfactory dendrites and facilitate their transfer to the odorant-receptor Orco complex. Heterodimer with conventional odorant receptors (ORs). Complexes exist early in the endomembrane system in olfactory sensory neurons (OSNs), coupling these complexes to the conserved ciliary trafficking pathway. Expression is restricted to olfactory sensory neurons (OSNs). Coexpressed with Snmp in a lateral-distal population of OSNs. Expressed in the embryonic antennal-maxillary complex, in all 21 OSNs of the larval dorsal organ, in the pupal antennal OSNs, in all 120 adult maxillary palp neurons and in approximately 70-80% of adult antennal OSNs, where expression is highest at the dorsal-medial edge. Localized to OSN cell bodies and to the distal portion of ciliated OSN dendrites. Expressed throughout all developmental stages. First expressed at embryonic stage 15. Pupal expression first occurs 80 hours after puparium formation. The atypical heteromeric and topological design of the odorant receptors appears to be an insect-specific solution for odor recognition, making the OR/Orco complex an attractive target for the development of highly selective insect repellents to disrupt olfactory-mediated host-seeking behaviors of insect disease vectors. Odor-evoked OR currents are independent of known G-protein-coupled second messenger pathways. The homomeric Orco channel is thought to be a cyclic-nucleotide-gated ion channel that depolarizes the olfactory receptor neuron. Belongs to the insect chemoreceptor superfamily. Heteromeric odorant receptor channel (TC 1.A.69) family. Orco subfamily.