Odorant‐Binding Proteins: Expression and Function

Abstract

Odorant-binding proteins (OBPs) are a major constituent of the aqueous perireceptor compartment in vertebrates and in insects. Although different in primary structure, they are supposed to serve similar functions in both animal groups: (i) OBPs may act as solubilizers and carriers of the lipophilic odorants in the aqueous mucus or sensillum lymph; (ii) OBPs may act in addition as peripheral filters in odor discrimination by selectively binding certain classes of odorants; (iii) OBPs may present the stimulus molecule in a particular way to the receptor proteins to facilitate signal transduction; (iv) OBPs may clean the perireceptor space from unwanted and toxic compounds; (v) OBPs may rapidly deactivate odorants after stimulation of the receptors. Experimental evidence in favor of this multiple role of OBPs is reviewed.

Functional characterization and immunolocalization of odorant binding protein 1 in the lucerne plant bug, Adelphocoris lineolatus (GOEZE)

“…There are several proposed functions of OBPs in odor and pheromone perception, including (i) transporting odorants or pheromones across the sensillum lymphs to the ORs, which can activate signal transduction process (Krieger and Breer, 1999); (ii) solubilizing hydrophobic odorants (Steinbrecht, 1998); (iii) concentrating odorants in the sensillum lymph (Steinbrecht, 1998); (iv) removing or deactivating odorants after stimulating the receptors (Vogt and Riddiford, 1981;Ziegelberger, 1995). However, the experimental data which support those supposed functions are exclusive.…”

Odorant responses of olfactory sensory neurons expressing the odorant receptor MOR23: A patch clamp analysis in gene-targeted mice

“…It contains complex components such as odorant binding proteins (OBPs; refs. [40][41][42], which may change the odorant concentrations that reach the cilia of the OSNs. When the odorant concentration is low, OBPs may help the odorant molecules to accumulate and deliver them to the cilia.…”

Natural Variation in Odorant Recognition Among Odorant-Binding Proteins in Drosophila melanogaster

“…OBPs are secreted by support cells in olfactory sensilla into the aqueous perilymph that surrounds olfactory dendrites and are thought to facilitate solubilization and transport of hydrophobic odorants, thereby either promoting or limiting access of odorants to odorant receptors (Steinbrecht 1998). For example, the pheromone-binding protein of the silk moth, Bombyx mori, binds and releases bombykol in a pH-dependent manner at the membrane interface (Wojtasek and Leal 1999;Sakurai et al 2004).…”