The <i>Anopheles gambiae</i> Odorant Binding Protein 1 (AgamOBP1) Mediates Indole Recognition in the Antennae of Female Mosquitoes

Haematophagous insects are frequently carriers of parasitic diseases, including malaria. The mosquito <i>Anopheles gambiae</i> is the major vector of malaria in sub-Saharan Africa and is thus responsible for thousands of deaths daily. Although the role of olfaction in <i>A. gambiae</i> host detection has been demonstrated, little is known about the combinations of ligands and odorant binding proteins (OBPs) that can produce specific odor-related responses <i>in vivo</i>. We identified a ligand, indole, for an <i>A. gambiae</i> odorant binding protein, AgamOBP1, modeled the interaction in silico and confirmed the interaction using biochemical assays. RNAi-mediated gene silencing coupled with electrophysiological analyses confirmed that AgamOBP1 binds indole in <i>A. gambiae</i> and that the antennal receptor cells do not respond to indole in the absence of AgamOBP1. This case represents the first documented instance of a specific <i>A. gambiae</i> OBP–ligand pairing combination, demonstrates the significance of OBPs in odor recognition, and can be expanded to the identification of other ligands for OBPs of <i>Anopheles</i> and other medically important insects.