Identification and cloning of a female antenna-specific odorant-binding protein in the mosquito Culex quinquefasciatus

Abstract—We have identified and cloned a cDNA encoding the first odorant-binding protein isolated from mosquitoes. The protein isolated from female an-tennae of Culex quinquefasciatus (CquiOBP) was not detected in legs (control tissue) or in antennal extracts from males, and showed mobility in native poly-acrylamide gels similar to that of the pheromone-binding protein from Bombyx mori. The open reading frame of the cloned cDNA encoded a hydrophobic sig-nal peptide (24 residues) and an acid mature protein (pI 5.5) of 125 amino acid residues (calculated molecular mass 14,504 Da). The transcript was detected by RT-PCR with antennal, but not with leg tissues. CquiOPB shared the high-est amino acid identity with a product deduced from Drosophila melanogaster PBPRP-3 cDNA (58.6%), OBPs from scarab beetles (35%), and moths (28%). In addition, CquiOBP showed the hallmark of insect odorant-binding proteins, the six Cys residues. Key Words—Odorant-binding protein, mosquito, Culex quinquefasciatus, Diptera, Culicidae