title: Endogenous fatty acids in olfactory hairs influence pheromone binding protein structure and function in Lymantria dispar.
abstract: The gypsy moth utilizes a pheromone, (7R,8S)-2-methyl-7,8-epoxyoctadecane, for mate location. The pheromone is detected by sensory hairs (sensilla) on the antennae of adult males. Sensilla contain the dendrites of olfactory neurons bathed in lymph, which contains pheromone binding proteins (PBPs). We have extracted and identified free fatty acids from lymph of sensory hairs, and we demonstrate that these function as endogenous ligands for gypsy moth PBP1 and PBP2. Homology modeling of both PBPs, and docking of fatty acids reveal multiple binding sites: one internal, the others external. Pheromone binding assays suggest that these fatty acids increase PBP-pheromone binding affinity. We show that fatty acid binding causes an increase in α-helix content in the N-terminal domain, but not in the C-terminal peptide of both proteins. The C-terminal peptide was shown to form a α-helix in a hydrophobic, homogeneous environment, but not in the presence of fatty acid micelles. Through partition assays we show that the fatty acids prevent adsorption of the pheromone on hydrophobic surfaces and facilitate pheromone partition into an aqueous phase. We propose that lymph is an emulsion of fatty acids and PBP that influence each other and thereby control the partition equilibria of hydrophobic odorants.
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5S 1S6, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Nardella
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5S 1S6, Canada.
authors.forename: Mailyn
authors.initials: M
authors.lastname: Terrado
authors.affiliation: The Centre for Drug Research and Development, 2405 Wesbrook Mall, 4th Floor, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Nicolette S
authors.initials: NS
authors.lastname: Honson
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5S 1S6, Canada. Electronic address: plettner@sfu.ca.
authors.forename: Erika
authors.initials: E
authors.lastname: Plettner
mesh_terms: D000327:Adsorption; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D019476:Insect Proteins / Q000737:chemistry / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D009036:Moths / Q000737:chemistry / Q000378:metabolism*; D010675:Pheromones / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D058618:Sensilla / Q000737:chemistry / Q000378:metabolism*; D012903:Smell / Q000502:physiology; D013329:Structure-Activity Relationship
chemical_list: D002352:Carrier Proteins; D005227:Fatty Acids; D019476:Insect Proteins; D036341:Intercellular Signaling Peptides and Proteins; C111001:PBP1 protein, Lymantria dispar; C111000:PBP2 protein, Lymantria dispar; D010675:Pheromones
keywords: Emulsion; Endogenous ligand; Fatty acid; Insect; Partition; Pheromone-binding protein