Odorant-binding proteins from a primitive termite

Hitherto, odorant-binding proteins (OBPs) have been identified from insects belonging to more highly evolved insect orders (Lepidoptera, Coleoptera, Diptera, Hymenoptera, and Hemiptera), whereas only chemosensory proteins have been identified from more primitive species, such as orthopteran and phasmid species. Here, we report for the first time the isolation and cloning of odorant-binding proteins from a primitive termite species, the dampwood termite, Zootermopsis nevadensis nevadensis (Isoptera: Termopsidae). A major antennae-specific protein was detected by native PAGE along with four other minor proteins, which were also absent in the extract from control tissues (hindlegs). Multiple cDNA cloning led to the full characterization of the major antennae-specific protein (ZnevOBP1) and to the identification of two other antennae-specific cDNAs, encoding putative odorant-binding proteins (ZnevOBP2 and ZnevOBP3). N-terminal amino acid sequencing of the minor antennal bands and cDNA cloning showed that olfaction in Z. n. nevadensis may involve multiple odorant-binding proteins. Database searches suggest that the OBPs from this primitive termite are homologues of the pheromone-binding proteins from scarab beetles and antennal-binding proteins from moths.     

Identification and Molecular Cloning of Putative Odorant-Binding Proteins and Chemosensory Protein from the Bethylid Wasp, <Emphasis Type="Italic">Scleroderma guani</Emphasis> Xiao et Wu

Two putative odorant-binding proteins (OBPs) and one putative chemosensory protein (CSP) from females of the ant-like bethylid wasp, Scleroderma guani Xiao et Wu (Hymenoptera: Bethylidae), were identified and cloned. The putative OBPs and CSP were identified by nondenaturing polyacrylamide gel electrophoresis (native-PAGE). 3′ rapid amplification of cDNA ends (3′RACE) was performed to obtain the sequences of the mature proteins by using degenerate primers designed from N-terminal sequences. Gene-specific primers for 5′ rapid amplification of cDNA ends (5′RACE) were designed according to 3′RACE results and used in polymerase chain reaction (PCR) to obtain full-length sequences. The proteins (Sgua-OBP1, Sgua-OBP2, and Sgua-CSP1) encode 133, 142, and 129 amino acid-deduced sequences, respectively. Prediction of signal peptide sequences matches the N-terminal amino acid sequence of the isolated proteins. Database searches suggest that the Sgua-OBP1 and Sgua-OBP2 are homologs of OBPs from other insects, and Sgua-CSP1 shares a high level of identity with previously described CSPs. Daguang Lu and Xiangrui Li contributed equally to this work     

<Emphasis Type="Italic">Ricinus communis</Emphasis> Contains an Acyl-CoA Synthetase that Preferentially Activates Ricinoleate to Its CoA Thioester

As part of our effort to identify enzymes that are critical for producing large amounts of ricinoleate in castor oil, we have isolated three cDNAs encoding acyl-CoA synthetase (ACS) in the castor plant. Analysis of the cDNA sequences reveals that two of them, designated RcACS 2 and RcACS 4, contain complete coding regions corresponding to 694 and 690 amino acids, respectively. The third cDNA, RcACS 1, encodes a truncated gene sequence. The RcACS 2 and RcACS 4 share 77% identity at the amino acid sequence level. Complementation tests showed that both RcACS 2 and RcACS 4 successfully restored growth of a yeast mutant strain (YB525) deficient in ACS. Lysates from yeast cells expressing RcACS 2 and 4 were enzymatically active when using ¹⁴C-labeled oleic acid as a substrate. A cell fractionation study indicates that RcACS 2 and 4 are mainly associated with membranes. Substrate specificity assays indicate that the RcACS 2 preferentially activates ricinoleate, while the RcACS 4 has a preference for nonhydroxy fatty acids.     

Identification and Expression Profile Analysis of Odorant Binding Proteins in the Oriental Fruit Fly Bactrocera dorsalis

Olfaction is crucial in many insects for critical behaviors, including those regulating survival and reproduction. Insect odorant-binding proteins (OBPs) function in the first step of the olfactory system and play an essential role in the perception of odorants, such as pheromones and host chemicals. The oriental fruit fly, Bactrocera dorsalis, is a destructive fruit-eating pest, due to its wide host range of up to 250 different types of fruits and vegetables, and this fly causes severe economic damage to the fruit and vegetable industry. However, OBP genes have not been largely identified in B. dorsalis. Based on our previously constructed B. dorsalis cDNA library, ten OBP genes were identified in B. dorsalis for the first time. A phylogenetic tree was generated to show the relationships among the 10 OBPs of B. dorsalis to OBP sequences of two other Dipteran species, including Drosophila melanogaster and the mosquito Anopheles gambiae. The expression profiles of the ten OBPs in different tissues (heads, thoraxes, abdomens, legs, wings, male antennae and female antenna) of the mated adults were analyzed by real-time PCR. The results showed that nine of them are highly expressed in the antenna of both sexes, except BdorOBP7. Four OBPs (BdorOBP1, BdorOBP4, BdorOBP8, and BdorOBP10) are also enriched in the abdomen, and BdorOBP7 is specifically expressed in leg, indicating that it may function in other biological processes. This work will provide insight into the roles of OBPs in chemoreception and help develop new pest-control strategies.     

Odorant Binding Characteristics of Three Recombinant Odorant Binding Proteins in Microplitis mediator (Hymenoptera: Braconidae)

Odorant binding proteins (OBPs) are believed to be important for transporting semiochemicals through the aqueous sensillar lymph to the olfactory receptor cells within the insect antennal sensilla. In this study, three new putative OBP genes, MmedOBP8-10, were identified from a Microplitis mediator (Hymenoptera: Braconidae) antennal cDNA library. Quantitative real-time PCR (qRT-PCR) analysis revealed that all three of the OBP genes were expressed mainly in the antennae of adult wasps. The three OBPs were recombinantly expressed in Escherichia coli and purified by Ni ion affinity chromatography. Fluorescence competitive binding assays were performed using N-phenyl-naphthylamine as a fluorescent probe and 45 small organic compounds as competitors. These assays demonstrated that the three M. mediator OBPs can bind a broad range of odorant molecules with different binding affinities. They can bind the following ligands: nonane, farnesol, nerolidol, nonanal, β-ionone, acetic ether, and farnesene. In a Y-tube assay with these ligands as odor stimuli and paraffin oil as a control, all ligands, except nerolidol and acetic ether, were able to elicit behavioral responses in adult M. mediator. The wasps were significantly attracted to β-ionone, nonanal, and farnesene and repelled by nonane and farnesol. The results of this work provide insight into the chemosensory functions of the OBPs in M. mediator.     

The Odorant-Binding Proteins of the Spider Mite Tetranychus urticae

Spider mites are one of the major agricultural pests, feeding on a large variety of plants. As a contribution to understanding chemical communication in these arthropods, we have characterized a recently discovered class of odorant-binding proteins (OBPs) in Tetranychus urticae. As in other species of Chelicerata, the four OBPs of T. urticae contain six conserved cysteines paired in a pattern (C1–C6, C2–C3, C4–C5) differing from that of insect counterparts (C1–C3, C2–C5, C4–C6). Proteomic analysis uncovered a second family of OBPs, including twelve members that are likely to be unique to T. urticae. A three-dimensional model of TurtOBP1, built on the recent X-ray structure of Varroa destructor OBP1, shows protein folding different from that of insect OBPs, although with some common features. Ligand-binding experiments indicated some affinity to coniferyl aldehyde, but specific ligands may still need to be found among very large molecules, as suggested by the size of the binding pocket.     

Molecular Characterization,Expression Pattern,and Ligand-Binding Property of Three Odorant Binding Protein Genes from Dendrolimus tabulaeformis

Odorant binding proteins (OBPs) play important roles in insect olfactory processes. The Chinese pine caterpillar moth, Dendrolimus tabulaeformis (Lepidoptera, Lasiocampidae) is a serious economic pest in China, and the pheromones of this species have been identified to monitor their presence. However, the molecular mechanisms by which D. tabulaeformis perceive pheromones and host volatiles remain unknown. In this study, we identified and characterized three new OBPs, including one pheromone binding protein (PBP1) and two general odor binding proteins (GOBPs), from antennal cDNA of D. tabulaeformis. The deduced amino acid sequences of DtabPBP1, DtabGOBP1, and DtabGOBP2 revealed mature proteins of 140, 147, and 140 amino acids, respectively. Each has six cysteine residues in conserved positions relative to other known OBPs. Amino-acid alignments indicated that the two GOBPs are more conserved (DtabGOBP1 is 52.9–67.4 % identical to orthologs from other Lepidoptera, and DtabGOBP2 is 55.2–81.8 % identical) than the PBP (32.5–46.0 %). Real-time PCR indicated tissue- and sex-specific expression patterns of the three genes. DtabPBP1 was mainly expressed in the antennae of males, whereas female antennae had only 1.09 % the expression in male antennae. Both DtabGOBP1 and DtabGOBP2 were more highly expressed in antennae than in other tissues, while DtabGOBP1 was more abundant in male antennae and DtabGOBP2 in female antennae. In addition, the binding specificities of the three proteins were investigated, and all three OBPs exhibited high binding affinities for the pheromone component (5Z,7E)-5,7-dodecadien-1-yl propionate (Z5,E7-12:OPr). This suggests a role in binding pheromone for GOBPs, as well as PBP1, in D. tabulaeformis.     

Phosphorylation of Native Porcine Olfactory Binding Proteins

The identification of various isoforms of olfactory binding proteins is of major importance to elucidate their involvement in detection of pheromones and other odors. Here, we report the characterization of the phosphorylation of OBP (odorant binding protein) and Von Ebner’s gland protein (VEG) from the pig, Sus scrofa. After labeling with specific antibodies raised against the three types of phosphorylation (Ser, Thr, Tyr), the phosphate-modified residues were mapped by using the beta-elimination followed by Michael addition of dithiothreitol (BEMAD) method. Eleven phosphorylation sites were localized in the pOBP sequence and nine sites in the VEG sequence. OBPs are secreted by Bowman’s gland cells in the extracellular mucus lining the nasal cavity. After tracking the secretion pathway in the rough endoplasmic reticulum of these cells, we hypothesize that these proteins may be phosphorylated by ectokinases that remain to be characterized. The existence of such a regulatory mechanism theoretically increases the number of OBP variants, and it suggests a more specific role for OBPs in odorant coding than the one of odorant solubilizer and transporter. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Chrystelle Le Danvic and Fanny Brimau contributed equally to the work.     

Odorant binding protein homologues of the malaria mosquito Anopheles gambiae; possible orthologues of the OS-E and OS-F OBPs OF Drosophila melanogaster

Twenty-nine Anopheles gambiae candidate Odorant Binding Proteins (OBPs) were characterized for similarity to OBPs of Drosophila melanogaster and other insects. Twenty-five of these sequences were identified by BLAST searching the A. gambiae genome database. Several A. gambiae sequences were significantly similar to the D. melanogaster OBPs OS-E/OS-F, LUSH and PBPRP2/PBPRP5. Exon boundary comparisons suggests that two A. gambiae genes are orthologues of OS-E and OS-F, justifying the names AgamOS-E (EAA01090, AF437886) and AgamOS-F (EAA14641, AF437884). If these are orthologues, then the gene duplication establishing the OS-E and OS-F lineages predated the divergence of mosquitoes and flies. The identification of orthologous OBPs and other chemosensory genes between D. melanogaster and A. gambiae should accelerate the transfer of physiological and behavioral information between these two species.     

Improvement of nutritional value and functional properties of soybean glycinin by protein engineering

Glycinin is one of the predominant storage proteins of soybean.To improve its functional properties (heat-induced gelationand emulsification) and/or nutritional value, the A_1aB_1b proglycininsubunit was modified on the basis of genetically variable domainssuggested from the comparison of amino acid sequences of glycinin-typeglobulins from various legumes and nonlegumes and the relationshipsbetween the structure and the functional properties of glycinin.Thus, nucleotide sequences corresponding to each of the variabledomains were deleted from the cDN A encoding the A_1aB_1b proglycinin,and a synthetic DNA encoding four continuous methionines wasinserted into the cDNA region corresponding to each of the variabledomains. Expression plasmids carrying the modified cDNAs wereconstructed and expressed in Escherichia coli strain JM105.Some of the modified proteins were accumulated as soluble proteinsin the cells at a high level and self-assembled. They exhibitedfunctional properties superior to those of the native glycininfrom soybean, which establishes the possibility of creatingtheoretically designed novel glycinins with high food qualities.     

Natural Ligands of Porcine Olfactory Binding Proteins

Knowledge of endogenous ligands of olfactory binding proteins is a prerequisite for studying their role in odor and pheromone transduction. Here, we report the extraction, derivatization, and characterization by gas chromatography-mass spectrometry of the natural ligands of pig, Sus scrofa (L.), Von Ebner’s Gland protein (VEG) and odorant binding protein (OBP). We identified two isoforms (VEG1 and VEG2), which differed only by the linkage of an O-N-acetylglucosamine (O-GlcNac) group on VEG1. The natural ligands of VEG1 were characterized as two isomers of testosterone, whereas ligands of VEG2 and OBP were fatty acids or their derivatives. Our findings suggest that the binding specificity of VEG1 for steroids is governed by the presence of an O-GlcNac moiety on the protein. This specificity was confirmed by the binding of radiolabeled testosterone only by VEG1 in an in-gel binding assay. This is the first evidence for a post-translational modification in the process of odorant discrimination by olfactory binding proteins.     

Analysis of the Insect OS-D-Like Gene Family

Insect OS-D-like proteins, also known as chemosensory (CSP) or sensory appendage proteins (SAP), are broadly expressed in various insect tissues, where they are thought to bind short to medium chain length fatty acids and their derivatives. Although their specific function remains uncertain, OS-D-like members have been isolated from sensory organs (including the sensillum lymph in some cases), and a role in olfaction similar to that of the insect odorant binding proteins (OBP) has been suggested for some. We have identified 15 new OS-D-like sequences: four from cDNA clones described herein and 11 from sequence databases. The os-d-like genes from the Anopheles gambiae, Apis mellifera, Drosophila melanogaster, and Drosophila pseudoobscura genomes typically have single, small introns with a conserved splice site. Together with all family members entered on GenBank, a total of 70 OS-D-like proteins, representing the insect orders Diptera, Dictyoptera, Hymenoptera, Lepidoptera, Orthoptera, and Phasmatodea, were analyzed. A neighbor joining distance phenogram identified several protein similarity classes that were characterized by highly conserved sequence motifs, including (A) N-terminal YTTKYDN(V/I)(N/D)(L/V)DEIL, (B) central DGKELKXX(I/L)PDAL, and (C) C-terminal KYDP. In contrast, three similarity classes were characterized by their diversion from these conserved motifs. The functional importance of conserved amino acid residues is discussed in relation to the crystal and NMR structures of MbraCSPA6.     

Biosynthetic Short Neuropeptides: A Rational Theory Based on Experimental Results for the Missing Pain-Relief Opioid Endomorphin Precursor Gene

Endomorphins are neuropeptides that bind strongly to μ-opioid receptors and are considered to play important roles in pain modulation and other biological functions. Two endomorphins have been identified, to date, endomorphine-1 and -2; both are tetrapeptides and differ by only a single amino acid in the third position. Both peptides were isolated from bovine brains; however, their precursor genes have not been identified. In this study, a nucleotide sequence corresponding to the endomorphin-1 peptide in an expressed sequence tag database has been found and a preproendomorphin-like precursor peptide from human brain complementary DNA (cDNA) has been cloned. The cDNA consists of nucleotide sequences of two already annotated predicted genes, and the putative peptide differs by one amino acid from the isolated endomorphin peptides. It is proposed herein that there is the possibility of unknown short proteins or peptide precursors being missed by automated gene prediction programs based on similarities of known protein sequences. A novel concept of how to produce endomorphins from a similar peptide is described. The oxidatively modified base might provide a clue for understanding discrepancies between nucleotide sequences on the genome and those on cDNAs.