Characterization of a Subfamily of Beetle Odorant-binding Proteins Found in Hemolymph

Abstract

In insects, hydrophobic odorants are transported through the sensillar lymph to receptors on sensory neurons by odorant-binding proteins (OBPs). The beetle Tenebrio molitor, which is a pest of stored grain products, produces a set of 12-14-kDa OBP-like proteins in its hemolymph. The structure of one of these proteins and that of a moth pheromone-binding protein have been solved. Both proteins have at least six ␣-helices with an internal, hydrophobic, ligand-binding pocket, but the beetle OBP lacks one of the disulfide bonds immediately adjacent to this pocket. To explore this difference and to sample isoform diversity, T. molitor hemolymph OBPs were fractionated by size-exclusion chromatography and reversedphase high performance liquid chromatography. Selected fractions were reduced and alkylated, and tryptic peptides were sequenced by tandem mass spectrometry. Partial sequences of 7 different isoforms were obtained and used to clone 9 new cDNAs encoding OBPs with identities from 32 to 99%. The more divergent isoforms have numerous substitutions of hydrophobic residues that presumably alter the shape and specificity of the ligand-binding pocket. These isoforms all lack the same third disulfide bridge and are more similar to one another than to any of the 38 OBPs in Drosophila melanogaster.

Identification of candidate chemosensory genes in the antennal transcriptome of Tenebrio molitor (Coleoptera: Tenebrionidae)

“…First, as we only sequenced the antennal transcriptome of T. molitor adults we may have missed OBP genes expressed specifically in other olfactory or nonolfactory organs (e.g. the maxillary palp, proboscis, legs, sex pheromone gland and hemolymph) or in other developmental stages, such as the larval stage (Graham et al, 2003;Gong et al, 2014;Zhou et al, 2014). Second, we cannot rule out variability in the number of OBP genes among insect species.…”

“…Thus, better understanding of the chemosensory gene families in T. molitor could help identify new targets for the development of novel control strategies. Previously, Graham et al (2003) identified seven OBP isoforms in the hemolymph of T. molitor larvae and cloned nine cDNAs encoding these OBP isoforms. In this study, we performed Illumina sequencing to identify chemosensory genes in the antenna of T. molitor.…”

Identification of a Novel Hemolymph Peptide That Modulates Silkworm Feeding Motivation

“…In addition, HemaP is abundant in the hemolymph (ϳ20 M). Although the complete amino acid sequence of HemaP shows no significant similarity with other proteins, similar ␣-helical characteristics and partial sequence similarities have been observed in other hemolymph proteins, such as lipophorins (insect lipoproteins) (27) and odorantbinding proteins (28). Therefore, HemaP might associate with some compounds possibly related to nutrients or metabolites.…”

Functional characterization and immunolocalization of odorant binding protein 1 in the lucerne plant bug, Adelphocoris lineolatus (GOEZE)

“…Insect OBP family can be divided into three major classes, pheromone binding proteins (PBPs) (Vogt and Riddiford, 1981), general odorant binding proteins (GOBP1 and GOBP2) (Vogt et al, 1991), and antennal binding proteins X (ABPX) (Krieger et al, 1996). So far, OBPs have been identified in many insect orders such as in Lepidoptera (Vogt and Riddiford, 1981), Orthoptera (Ban et al, 2003), Isoptera (Krieger and Ross, 2002), Diptera (Xu et al, 2003), Hymenoptera , Hemiptera (Dickens et al, 1995) and Coleoptera (Graham et al, 2003).…”