Present in the aqueous fluid surrounding olfactory sensory dendrites and are thought to aid in the capture and transport of hydrophobic odorants into and through this fluid. Exclusively or primarily restricted to the olfactory system. Expressed in all olfactory sensilla including antenna, maxillary palp, proboscis, other adult chemosensory and larval chemosensory organ. Also expressed in the wing and tarsal gustatory sensilla and dorsal organ. Expressed in larval hemolymph. Belongs to the PBP/GOBP family.