On a chip demonstration of a functional role for odorant binding protein in the preservation of olfactory receptor activity at high odorant concentration

Abstract

The molecular mechanisms underlying odorant detection have been investigated using the chip based SPR technique by focusing on the dynamic interactions between transmembrane Olfactory Receptor OR1740, odorant ligands and soluble Odorant-Binding Protein (OBP-1F). The OR1740 present in the lipid bilayer of nanosomes derived from transformed yeasts specifically bound OBP-1F. The receptor preferential odorant ligand helional released bound OBP-1F from the OR-OBP complex, while unrelated odorants failed to do so. OBP-1F modified the functional OR1740 dose-response to helional, from a bell-shaped to a saturation curve, thus preserving OR activity at high ligand concentration. This unravels an active role for OBPs in olfaction, in addition to passive transport or a scavenger role. This sensorchip technology was applied to assessing native OBP-1F in a biological sample: rat olfactory mucus also displayed significant binding to OR1740 nanosomes, and the addition of helional yielded the dissociation of mucus OBP from the receptor.

Relationship between Homo-oligomerization of a Mammalian Olfactory Receptor and Its Activation State Demonstrated by Bioluminescence Resonance Energy Transfer

“…Some ORs, including human OR1740, were reported not to heterodimerize with a non-olfactory GPCR, the ␤ 2 -adrenergic receptor (15). Our previous studies (6,16,17), in line with others (18,19), showed a bell-shaped OR dose-response curve upon odorant stimulation. Several assumptions have been raised to elucidate the decreased OR response at high ligand concentrations (20 -22).…”

“…In insects, OBPs are thought to interact with ORs and play a scavenger role to maintain ORs in an active conformation (5). We have recently demonstrated a tripartite functional interaction between OBPs, odorants, and ORs in mammals (6).…”

Ligand-Binding Proteins: Structure, Stability and Practical Application

“…As already mentioned, the spectrum of OBPs in animal species can be expanded through phosphorylation and glycosylation. Further, it has been shown with the chip based surface plasmon resonance technique that the OBP is able to modulate the activity of olfactory receptors (Vidic et al, 2008). Some evidence for subtle conformational changes in rat and porcine OBPs after ligand binding has been obtained in molecular dynamics studies wherein opening of the -strand pair was observed (Hajjar et al, 2006).…”

Highly sensitive and selective odorant sensor using living cells expressing insect olfactory receptors

“…Additionally, we think that systems for the solubilization of ligands into the device will help our system. Although ligands are dissolved by DMSO in this study, gas permeable materials and usages of odorant-binding proteins will be useful for incorporation of volatile chemicals into the fluidic device (32).…”