Structural and Functional Characterization of European Corn Borer, Ostrinia nubilalis, Pheromone Binding Protein 3

Backbone and side chain NMR assignments and secondary structure calculation of the pheromone binding protein3 of Ostrinia nubilalis, an agricultural pest

Ostrinia nubilalis, also known as European Corn Borer (ECB), is a serious pest in Europe and North America, as well as in Central Asia and Northern Africa. It damages a variety of agricultural crops such as corn, oats, buckwheat, millet, and soybeans. causing annually at least one billion dollars in loss. The Ostrinia nubilalis pheromone-binding protein3 (OnubPBP3), preferentially expressed in the male moth antenna, has been implicated in the detection of the female-secreted pheromone blend during the mating process. Understanding the structure of and function of OnubPBP3, including the mechanism of pheromone binding and its release at the dendritic olfactory neuron (ORN), is essential if integrated pest management through sensory inhibition is to be achieved. We report here the backbone and side-chain resonance assignments of OnubPBP3 at pH 6.5 using various triple resonance NMR experiments on a 13C, 15N-labeled protein sample. The secondary structure of OnubPBP3 consists of six α-helices and an unstructured C-terminus based on backbone chemical shifts.

Functional disparity of four pheromone-binding proteins from the plum fruit moth Grapholita funebrana Treitscheke in detection of sex pheromone components

Grapholita funebrana, also known as the plum fruit moth, is an oligophagous pest species that causes enormous economic losses of the fruits of Rosaceae. An eco-friendly method for the control of G. funebrana besides chemical control has not yet been developed. The sex pheromone communication system plays an important role in moth courtship and mating, in which pheromone-binding proteins (PBPs) are critical. In this research, we identified four PBPs, namely, GfunPBP1.1, GfunPBP1.2, GfunPBP2, and GfunPBP3, from the antennae of G. funebrana. The results of real-time quantitative PCR (RT-qPCR) showed that all four GfunPBPs were overwhelmingly expressed in the antennae and that GfunPBP1.2 and GfunPBP2 showed male-biased expression patterns, whereas GfunPBP1.1 and GfunPBP3 were equally expressed between sexes. The results of ligand-binding assays illustrated that although all four recombinant GfunPBPs (rGfunPBPs) had binding activity with the tested sex pheromone compounds, their preferred ligands were significantly different. rGfunPBP2 had the strongest binding affinity to Z8-12:Ac and Z8-12:OH; rGfunPBP1.1 preferred to bind Z8-14:Ac, Z10-14:Ac, and 12:OH more than to the other three GfunPBPs; and rGfunPBP1.2 exhibited stronger binding affinity to E8-12:Ac than to the other rGfunPBPs. Molecular docking results demonstrated that hydrophobic forces, especially van der Waals forces and hydrogen bonds, were the most important forces that maintained GfunPBP-pheromone ligand complexes. This study will improve our understanding of the sex pheromone recognition mechanisms of G. funebrana and promote the development of novel strategies for controlling G. funebrana.

Ostrinia furnacalis PBP2 solution NMR structure: Insight into ligand binding and release mechanisms

Ostrinia furnacalis is an invasive lepidopteran agricultural pest that relies on olfaction for mating and reproduction. Male moths have an extremely sensitive olfactory system that can detect the sex pheromones emitted by females over a great distance. Pheromone-binding proteins present in the male moth antenna play a key role in the pheromone uptake, transport, and release at the dendritic membrane of the olfactory neuron. Here, we report the first high-resolution NMR structure of a pheromone-binding protein from an Ostrinia species at pH 6.5. The core of the Ostrinia furnacalis PBP2 (OfurPBP2) consists of six helices, α1a (2-14), α1b (16-22), α2 (27-37), α3 (46-60), α4 (70-80), α5 (84-100), and α6 (107-124) surrounding a large hydrophobic pocket. The structure is stabilized by three disulfide bridges, 19-54, 50-108, and 97-117. In contrast to the unstructured C-terminus of other lepidopteran PBPs, the C-terminus of OfurPBP2 folds into an α-helix (α7) at pH 6.5. The protein has nanomolar affinity towards both pheromone isomers. Molecular docking of both pheromones, E-12 and Z-12-tetradecenyl acetate, to OfurPBP2 revealed that the residues Met5, Lys6, Met8, Thr9, Phe12, Phe36, Trp37, Phe76, Ser115, Phe118, Lys119, Ile122, His123, and Ala128 interact with both isomers, while Thr9 formed a hydrogen bond with the acetate head group. NMR structure and thermal unfolding studies with CD suggest that ligand release at pH 4.5 is likely due to the partial unfolding of the protein.