odorantbinding

Odorant-binding refers to the interaction between volatile chemical cues and specialized binding proteins that solubilize and shuttle odorants to olfactory receptors. The term most often denotes odorant-binding proteins (OBPs), a class of small, soluble proteins found in the sensory tissues of many animals. In insects, OBPs are secreted into the lymph of olfactory sensilla where they bind a wide range of odors, including pheromones and plant volatiles, and deliver them to odorant receptors on olfactory receptor neurons. In vertebrates, odorant-binding activity is provided by members of the lipocalin superfamily, which carry odorants in nasal mucus and related secretions, facilitating detection by olfactory receptors.

Structural features vary among groups. Classic insect OBPs are typically about 15–20 kDa and consist of six alpha-helices held together by multiple disulfide bonds formed by conserved cysteine motifs. Variants known as Plus-C and Minus-C OBPs show altered cysteine patterns and sometimes expanded binding pockets. Vertebrate OBPs generally belong to the lipocalin fold, with a characteristic beta-barrel that creates a hydrophobic ligand-binding cavity.

Functionally, OBPs bind hydrophobic, volatile ligands in aqueous environments, increasing apparent solubility, protecting ligands from degradation, and shaping the odorant profile that reaches receptors. Ligand release is thought to be triggered by concentration or pH changes near the receptor, enabling rapid signaling. OBP gene families are large and rapidly evolving, contributing to species-specific odor detection and behavior.

Applications include pest management and biosensor design, where understanding OBP-ligand interactions enables targeted disruption or detection of odor cues.