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BMC Biol

Title:		Putative ligand binding sites of two functionally characterized bark beetle odorant receptors
Author(s):		Yuvaraj JK; Roberts RE; Sonntag Y; Hou XQ; Grosse-Wilde E; Machara A; Zhang DD; Hansson BS; Johanson U; Lofstedt C; Andersson MN;
Address:		"Department of Biology, Lund University, SE-223 62, Lund, Sweden. Division of Biochemistry and Structural Biology, Department of Chemistry, Lund University, SE-223 62, Lund, Sweden. Department of Evolutionary Neuroethology, Max Planck Institute for Chemical Ecology, 07745, Jena, Germany. Present address: Faculty of Forestry & Wood Sci, Excellent Team for Mitigation, Czech University Life Sci Prague, Kamycka 129, Prague 6, 16521, Suchdol, Czech Republic. Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Gilead Sciences and IOCB Research Center, Flemingovo n. 2, 166 10, Prague 6, Czech Republic. Department of Biology, Lund University, SE-223 62, Lund, Sweden. martin_n.andersson@biol.lu.se"
Journal Title:		BMC Biol
Year:		2021
Volume:		20210126
Issue:		1
Page Number:		16 -
DOI:		10.1186/s12915-020-00946-6
ISSN/ISBN:		1741-7007 (Electronic) 1741-7007 (Linking)
Abstract:		"BACKGROUND: Bark beetles are major pests of conifer forests, and their behavior is primarily mediated via olfaction. Targeting the odorant receptors (ORs) may thus provide avenues towards improved pest control. Such an approach requires information on the function of ORs and their interactions with ligands, which is also essential for understanding the functional evolution of these receptors. Hence, we aimed to identify a high-quality complement of ORs from the destructive spruce bark beetle Ips typographus (Coleoptera, Curculionidae, Scolytinae) and analyze their antennal expression and phylogenetic relationships with ORs from other beetles. Using 68 biologically relevant test compounds, we next aimed to functionally characterize ecologically important ORs, using two systems for heterologous expression. Our final aim was to gain insight into the ligand-OR interaction of the functionally characterized ORs, using a combination of computational and experimental methods. RESULTS: We annotated 73 ORs from an antennal transcriptome of I. typographus and report the functional characterization of two ORs (ItypOR46 and ItypOR49), which are responsive to single enantiomers of the common bark beetle pheromone compounds ipsenol and ipsdienol, respectively. Their responses and antennal expression correlate with the specificities, localizations, and/or abundances of olfactory sensory neurons detecting these enantiomers. We use homology modeling and molecular docking to predict their binding sites. Our models reveal a likely binding cleft lined with residues that previously have been shown to affect the responses of insect ORs. Within this cleft, the active ligands are predicted to specifically interact with residues Tyr84 and Thr205 in ItypOR46. The suggested importance of these residues in the activation by ipsenol is experimentally supported through site-directed mutagenesis and functional testing, and hydrogen bonding appears key in pheromone binding. CONCLUSIONS: The emerging insight into ligand binding in the two characterized ItypORs has a general importance for our understanding of the molecular and functional evolution of the insect OR gene family. Due to the ecological importance of the characterized receptors and widespread use of ipsenol and ipsdienol in bark beetle chemical communication, these ORs should be evaluated for their potential use in pest control and biosensors to detect bark beetle infestations"
Keywords:		"Animals Binding Sites Female Insect Proteins/*chemistry/genetics Ligands Male Receptors, Odorant/*chemistry/genetics Weevils/*chemistry/genetics Deorphanization Functional evolution HEK293 cells Odorant receptor Pest insect Pheromone receptor Xenopus oocy;"
Notes:		"MedlineYuvaraj, Jothi K Roberts, Rebecca E Sonntag, Yonathan Hou, Xiao-Qing Grosse-Wilde, Ewald Machara, Ales Zhang, Dan-Dan Hansson, Bill S Johanson, Urban Lofstedt, Christer Andersson, Martin N eng 217-2014-689/Svenska Forskningsradet Formas/ 2018-01444/Svenska Forskningsradet Formas/ 2017-03804/Vetenskapsradet/ CTS 17:25/Carl Tryggers Stiftelse for Vetenskaplig Forskning/ Research Support, Non-U.S. Gov't England 2021/01/28 BMC Biol. 2021 Jan 26; 19(1):16. doi: 10.1186/s12915-020-00946-6"