The multiple role of the pheromone-binding protein in olfactory transduction

Before airborne odorant molecules can stimulate the olfactory receptor cells of animals that live on land, they have to pass through an aqueous solution that contains high concentrations of soluble odorant-binding proteins (OBPs). In insect sensilla the role of these OBPs for signal transduction is becoming multifaceted. Sensillum lymph perfusion experiments in the moth Antheraea polyphemus implied a solubilizer and carrier function of the pheromone-binding protein (PBP) and led to the conclusion that it is the pheromone-PBP complex which activates the postulated receptors. Recent results have shown the presence of two redox states of the PBP and a shift in pheromone binding from the reduced to the oxidized form, depending on the presence of sensory hair material. Thus, PBP oxidation might occur simultaneously with receptor cell activation and might lead to deactivation of the pheromone-PBP complex terminating the pheromone stimulation.