Acetylcholinesterase target sites for developing environmentally friendly insecticides against Tetranychus urticae (Acari: Tetranychidae).

The non-target toxicity and resistance problems of acetylcholinesterase (AChE) insecticides, such as organophosphates and carbamates, are of growing concern. To explore the potential targets for achieving inhibitor selectivity, the AChE structures at or near the catalytic pocket of Tetranychus urticae (TuAChE), honey bees, and humans were compared. The entrances to the AChE catalytic pocket differ significantly because of their different peripheral sites. The role of these potential mite-specific sites in AChE function was further elucidated by site-directed mutagenesis of these sites and then examining the catalytic activities of TuAChE mutants. The spider mite E316, H369, and V105 active sites are important for AChE function. By further analyzing their physostigmine inhibitory properties and the detailed interaction between physostigmine and TuAChE, the peripheral site H369 locating near the gorge entrance, and S154 at the oxyanion hole, affects substrate and inhibitor trafficking. The discovery of conserved mite-specific residues in Tetranychus will enable the development of safer, effective pesticides that target residues present only in mite AChEs, potentially offering effective control against this important agricultural pest.