Identification and cloning of a pheromone-binding protein from the oriental beetle, Exomala orientalis

We have identified and cloned a pheromone-binding protein (EoriPBP) from th e Japanese and American populations of the Oriental beetle, Exomala orienta lis (Coleoptera: Scarabaeidae). The protein showed more than 90% amino acid identity to the previously identified pheromone-binding proteins from Popi llia japonica (PjapPBP) and Anomala osakana (AosaPBP), as well as to one of the odorant-binding proteins from Phyllopertha diversa (PdivOBP1). EoriPBP has 116 amino acids, with a calculated molecular mass of 12,981 Da, pI of 4.3, and six highly conserved cysteine residues. 5'-RACE amplifications led to the characterization of a signal peptide with 19 amino acids. The signa l peptide showed high amino acid identity to the signal peptide for AosaPBP . Comparison of the amino acid sequences of the PBPs involved in the detect ion of similar ligands, i.e., monounsaturated lactones and ketone, suggests that the most variable residues among the PBPs from E. orientalis, P. japo nica, and A. osakana are probably the most discriminating residues. As with the pheromone-binding protein from Bombyx mori, the residues at positions 61, 64, 71, and 82 in EoriPBP, PajpPBP, and AosaPBP, which are either valin e, leucine, isoleucine, or methionine, are likely to be specificity determi nants.