Pheromone-binding proteins of scarab beetles.

We have characterized pheromone binding proteins (PBPs) present in the antennae of several species of scarab beetles. In most cases there was only one class of PBP, which was expressed in both sexes. Both Anomala osakana++ and Popillia japonica possess a single PBP, highly homologous to each other. In species the same PBP seems to recognize both enantiomers of japonilure, which have opposite biological functions, i.e., the sex pheromone and the behavioral antagonist (stop signal). The purified PBP of A. osakana binds both enantiomers apparently with the same low affinity. Unexpectedly, these ligands were bound by moth PBPs, which utilize pheromones with unrelated structures. These findings suggest that the ligand specificity in this class of proteins may not be as high as it has been postulated.