Structural and biochemical evaluation of Ceratitis capitata odorant-binding protein 22 affinity for odorants involved in intersex communication

A - Papers appearing in refereed journals

Falchetto, M., Ciossani, G., Scolari, F., Di Cosimo, A., Nenci, S., Field, L. M., Mattevi, A., Zhou, J-J., Gasperi, G. and Forneris, F. 2019. Structural and biochemical evaluation of Ceratitis capitata odorant-binding protein 22 affinity for odorants involved in intersex communication . Insect Molecular Biology. 28 (3), pp. 431-443.

AuthorsFalchetto, M., Ciossani, G., Scolari, F., Di Cosimo, A., Nenci, S., Field, L. M., Mattevi, A., Zhou, J-J., Gasperi, G. and Forneris, F.
Abstract

In 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/pheromonebinding 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 [half maximal effective concentration (EC50) = 0.48 µM] was to (E,E)-α-farnesene, one of the most abundant compounds in the male pheromone blend. This odorant was used in cocrystallization experiments, yielding the structure of CcapOBP22. The monomeric structure shows the typical OBP folding, constituted by six α-helical elements interconnected by three disulphide bridges. A C-terminal seventh α-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 seven-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 intersex olfactory communication.

KeywordsMedfly; Odorant-binding proteins; CcapOBP22; Pheromone components; Intersex communication; Olfaction
Year of Publication2019
JournalInsect Molecular Biology
Journal citation28 (3), pp. 431-443
Digital Object Identifier (DOI)doi:10.1111/imb.12559
PubMed ID30548711
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeBBSRC Strategic Programme in Smart Crop Protection
Output statusPublished
Publication dates
Online17 Jan 2019
Publication process dates
Accepted12 Dec 2018
Copyright licensePublisher copyright
PublisherWiley
ISSN0962-1075

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