Porcine odorant-binding protein selectively binds to a human olfactory receptor.
Odorant-binding proteins (OBPs) represent a highly abundant class of proteins secreted in the nasal mucus by the olfactory neuroepithelium. These proteins display binding affinity for a variety of odorant molecules, thereby assuming the role of carrier during olfactory perception. However, no specific interaction between OBP and olfactory receptors (ORs) has yet been shown and early events in olfaction remain so far poorly understood at a molecular level. Two human ORs, OR 17-209 and OR 17-210, were fused to a Green Fluorescent Protein and stably expressed in COS-7 cell lines. Interaction with OBP was investigated using a highly purified radioiodinated porcine OBP (pOBP) preparation, devoid of any ligand in its binding cavity. No specific binding of the pOBP tracer could be detected with OR 17-209. In contrast, OR 17-210 exhibited specific saturable binding (K(d) = 9.48 nM) corresponding to the presence of a single class of high-affinity binding sites (B(max) = 65.8 fmol/mg prot). Association and dissociation kinetics further confirmed high-affinity interaction between pOBP and OR 17-210. Autoradiographic studies of labeled pOBP to newborn mouse slices revealed the presence of multiple specific binding sites located mainly in olfactory tissue but also in several other peripheral tissues. Our data thus demonstrate a high-affinity interaction between OBP and OR, indicating that under physiological conditions, ORs may be specifically associated with an OBP partner in the absence of odorant. This provides further evidence of a novel role for OBP in the mechanism of olfactory perception.
Matarazzo
Valéry
V
Laboratoire de Neuroglycobiologie, IFR du Cerveau, GLM-CNRS, 31 Chemin J. Aiguier, F-13402 Marseille cedex 20, France.
Zsürger
Nicole
N
Guillemot
Jean-Claude
JC
Clot-Faybesse
Olivier
O
Botto
Jean-Marie
JM
Dal Farra
Claude
C
Crowe
Marc
M
Demaille
Jacques
J
Vincent
Jean-Pierre
JP
Mazella
Jean
J
Ronin
Catherine
C
D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002851:Chromatography, High Pressure Liquid; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D015723:Gene Library; D049452:Green Fluorescent Proteins; D006801:Humans; D007700:Kinetics; D008164:Luminescent Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018613:Microscopy, Confocal; D009831:Olfactory Mucosa / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018035:Receptors, Odorant / Q000737:chemistry* / Q000378:metabolism; D015398:Signal Transduction; D013552:Swine; D013737:Testis / Q000166:cytology; D013997:Time Factors; D014162:Transfection
D018076:DNA, Complementary; D008164:Luminescent Proteins; D018035:Receptors, Odorant; C109883:odorant receptor 17; C045648:odorant-binding protein; D049452:Green Fluorescent Proteins