The functions of odorant binding proteins as a whole is not well understood. They are generally believed to increase the solubility of hydrophobic odorants by binding them and transporting them across the aqueous sensillum lymph to receptors in the dendrites, and several studies support a role for OBPs in olfactory perception
in vivo. Some odorant binding proteins are hypothesized to hasten odor response termination by extracting odorant molecules from the sensillar lymph or from receptors themselves. Presently, just one OBP, Obp76a, has been thoroughly investigated in the olfactory system of
Drosophila and has a known physiological role. Obp76a, better known as LUSH, is located trichoid sensilla and is necessary for normal response of the odor receptor Or67d to its pheromone ligand
cis-vaccenyl acetate (cVA), although responses of Or67d to cVA have been detected in the absence of Obp76a LUSH has also been found to bind cVA
in vitro and is known to bind other insect pheromones, short-chain alcohols, and
phthalates. In 2016, Larter et al. found that the deletion of the sole abundant OBP, Obp28a, in ab8 sensilla of
Drosophila does not reduce the magnitude of their olfactory responses, suggesting that Obp28a is not required for odorant transport and that ab8 sensilla do not require an abundant OBP. Their results further suggest Obp28a may be buffering changes in the odor environment, possibly as molecular gain control, which has not been previously reported for OBPs. OBPs are thought to have multiple roles besides olfaction, including reproduction, egg laying and antiinflammatory responses. == Expression ==