Heterogeneity of odorant-binding proteins in the antennae of Bombyx mori

Different odorant-binding proteins (OBPs) were isolated from total antennal homogenates of male and female Bombyx mori. Proteins were separated according to their isoelectric point by using preparative fast-flow isoelectrofocusing. Odorant-binding proteins were identified in immunoblots by antisera raised against the pheromone-binding protein (anti-PBP) and the general odorant-binding protein (anti-GOBP2) of Antheraea polyphemus. Four proteins cross-reacting with anti-PBP were detected in males and two in females, while three proteins cross-reacting with anti-GOBP2 were found in males and five in females. Both anti-PBP and anti-GOBP2 cross-reacting proteins had an apparent molecular weight of 15-16 kDa. In parallel, the same two antisera were used in immunocytochemical studies in order to determine the distribution of these proteins within the various subtypes of olfactory sensilla. The presence of multiple odorant-binding proteins within one moth species as well as their complex distribution pattern support the suggestion that soluble OBPs might have a function in odorant discrimination.