The identification of insecticyanin with high insecticide-binding affinity in Spodoptera exigua

The transport mechanism of hydrophobic insecticides in insect hemolymph remains poorly understood. Here, we identified five insecticyanin genes (SeIns1-5) in Spodoptera exigua, which evolved from apolipoprotein D within the lipocalin family. Structural modeling revealed that SeIns1, SeIns3, and SeIns5 form a typical β-barrel ligand-binding pocket, while SeIns4 exhibits a disrupted structure. Molecular docking and microscale thermophoresis demonstrated that SeIns1 specifically binds λ-cyhalothrin (K_d = 9.04 μM) and chlorpyrifos (K_d = 105.24 μM) with high affinity, whereas other insecticyanins showed no binding. These findings demonstrate the high-affinity binding of SeIns1 to insecticides and suggest its potential role in insecticide transport, thereby providing a new perspective for understanding insecticide toxicology and resistance mechanisms.