Crystal and solution structures of an odorant-binding protein from the southern house mosquito complexed with an oviposition pheromone

Abstract

Culex mosquitoes introduce the pathogens responsible for filariasis, West Nile virus, St. Louis encephalitis, and other diseases into humans. Currently, traps baited with oviposition semiochemicals play an important role in detection efforts and could provide an environmentally friendly approach to controlling their populations. The odorant binding proteins (OBPs) in the female's antenna play a crucial, if yet imperfectly understood, role in sensing oviposition cues. Here, we report the X-ray crystallography and NMR 3D structures of OBP1 for Culex quinquefasciatus (CquiOBP1) bound to an oviposition pheromone (5R,6S)-6-acetoxy-5-hexadecanolide (MOP). In both studies, CquiOBP1 had the same overall six-helix structure seen in other insect OBPs, but a detailed analysis revealed an important previously undescribed feature. There are two models for OBPmediated signal transduction: (i) direct release of the pheromone from an internal binding pocket in a pH-dependent fashion and (ii) detection of a pheromone-induced conformational change in the OBP·pheromone complex. Although CquiOBP1 binds MOP in a pHdependent fashion, it lacks the C terminus required for the pHdependent release model. This study shows that CquiOBP binds MOP in an unprecedented fashion using both a small central cavity for the lactone head group and a long hydrophobic channel for its tail.AaegOBP1 | AgamOBP1 | CquiOBP1 | NMR | X-ray crystallography

Genome sequence of the Asian Tiger mosquito,Aedes albopictus, reveals insights into its biology, genetics, and evolution

“…albopictus genome (Table 3 and SI Appendix, Table S6.1). All the OBPs are members of the pheromone-binding protein (PBP)/GOBP family, 47 of which are PBPs with putative functions associated with communication (42)(43)(44)(45). Orthologs of 156 of the OR genes could be found in Ae.…”

Crystal and Solution Studies of the “Plus-C” Odorant-binding Protein 48 from Anopheles gambiae

“…Dimerization of insect OBPs in solution has been reported several times (20 -24) and has been also identified in the crystal state by x-ray crystallography since nearly all determined OBP crystal structures represent dimers (6,14,(25)(26)(27). The dimerization of OBPs has been proposed to create new binding sites at the interface between the two subunits leading to the formation of dimers with binding features different from those of the monomeric proteins (6,22,28).…”

Insect olfaction from model systems to disease control

“…OBPs were first identified in the silk moth, Antheraea polyphemus (39), and large families of OBPs have since been identified in many other insects (40). The structure and binding mechanisms of OBPs of several species have been analyzed (41)(42)(43)(44), and their expression patterns are diverse, with overlapping subsets of OBPs found in different sensilla (45).…”