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Crystal structure of the medfly Odorant Binding Protein CcapOBP22/CcapOBP69aCrystal structure of the medfly Odorant Binding Protein CcapOBP22/CcapOBP69a
Structural highlights
Publication Abstract from PubMedIn insects, odorant-binding proteins (OBPs) connect the peripheral sensory system to receptors of olfactory organs. Medfly Ceratitis capitata CcapObp22 shows 37% identity and close phylogenetic affinities with Drosophila melanogaster OBP69a/PB-PRP1 (pheromone-binding protein related protein 1). The CcapObp22 gene is transcribed in the antennae and maxillary palps, suggesting an active role in olfaction. Here, we recombinantly produced CcapObp22, obtaining a 13.5 kDa protein capable of binding multiple strongly hydrophobic terpene compounds, including medfly male pheromone components. The highest binding affinity (EC50 0.48 muM) was to (E,E)-alpha-farnesene, one of the most abundant compounds in the male pheromone blend. This odorant was used in co-crystallization experiments, yielding the structure of CcapOBP22. The monomeric structure shows the typical OBP folding, constituted by six alpha-helical elements interconnected by three disulfide bridges. A C-terminal seventh alpha-helix constitutes the wall of a deep, L-shaped hydrophobic cavity. Analysis of the electron density in this cavity suggested trapping of farnesene in the crystal structure, although with partial occupancy. Superposition of the CcapOBP22 structure with related 7-helical OBPs highlights striking similarity in the organization of the C-terminal segment of these proteins. Collectively, our molecular and physiological data on medfly CcapOBP22 suggest its involvement in inter-sex olfactory communication. This article is protected by copyright. All rights reserved. Structural and biochemical evaluation of Ceratitis capitata OBP22 affinity for odorants involved in inter-sex communication.,Falchetto M, Ciossani G, Scolari F, Di Cosimo A, Nenci S, Field LM, Mattevi A, Zhou JJ, Gasperi G, Forneris F Insect Mol Biol. 2018 Dec 12. doi: 10.1111/imb.12559. PMID:30548711[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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