Selective and pH-dependent binding of a moth pheromone to a pheromone-binding protein

Fluorescence and circular dichroism (CD) data suggest that the major pheromone-binding protein (PBP) from the wild silkmoth, Antheraea polyphemus, ApolPBP1, undergoes a pH-dependent conformational change similar to that previously observed for the PBP from the silkworm moth, Bombyx mori, BmorPBP. All three constituents of the sex pheromone, E6,Z11-16Ac, E6,Z11-16Ald, and E4,Z9-14Ac, bound to ApolPBP1 with apparent high affinity at high pH, but reduced binding at low pH when tested individually in a cold binding assay. In competitive assays, however, ApolPBP1 showed considerable preference for the major constituent of the sex pheromone, E6,Z11-16Ac. These data suggest that specificity of PBPs contributes at least in part to the remarkable selectivity of moth's olfactory system.