Mechanism and dynamics of insect odorant-binding proteins

Abstract

Abstract Insect odorant-binding proteins (OBPs) are small, soluble, insect-specific proteins that bind lipids and volatile compounds reversibly. In this chapter we review the context in which OBPs occur, their structural variations and their ligand association and dissociation mechanisms. OBPs occur in any context that requires modulation of the location and availability of lipids (e.g. fatty acids, hydrocarbons), pheromones, general odorants and other hydrophobic or amphiphilic compounds. These proteins have evolved into a large family with highly diverse primary sequences, but a conserved structural core. This core consists of six alpha helices, interlinked by at least two and often three disulfide bridges. Long and medium-length OBPs have a C-terminal segment that can either be alpha helical or unstructured, depending on the conditions such as ligand availability or pH. Based on structural and kinetic studies, the C-terminal segment of those proteins participates in ligand association and dissociation mechanisms.