Objective The aim is to screen potential small molecule inhibitors of methuselah-like (Ldmthl1) protein through virtual screening technology and explore the inhibitory ability of potential compounds on Ldmthl1 protein through molecular dynamics simulation, MM-PBSA, and bioassays. It lays a theoretical foundation for developing new insecticides targeting Lymantria dispar Ldmthl1.

Method The homology model of Ldmthl1 receptor was constructed in Lymantria dispar for virtual screening the small molecule inhibitors of the Ldmthl1 receptor. The binding strength of 6 potential small molecule inhibitors to Ldmthl1 receptor was analyzed by using molecular dynamics and MM-PBSA; The toxicity of 6 potential small molecule inhibitors was analyzed by bioassay, and the synergistic effect of the six potential compounds was explored by combining them with deltamethrin.

Result Ldmthl1 contained 7 transmembrane structures, which was consistent with the structural characteristics of G protein-coupled receptors, and met the evaluation criteria of protein models; 20 candidate compounds were obtained by molecular docking, and 6 small molecule compounds were identified as potential inhibitors based on the binding models and binding energies; Molecular dynamics simulations showed that 6 potential small molecule inhibitors were stably bound to Ldmthl1 receptors through hydrogen bonding and hydrophobic forces; The MM-PBSA calculation of binding free energy revealed that 6 potential small molecule inhibitors were tightly bound to the Ldmthl1 receptor; The lethal concentration of LC₃₀ deltamethrin and 6 inhibitors were combined to feed the 3rd instars of Lymantria dispar larvae at the ratio of 1 : 1, 1 : 2 and 2 : 1. The combination of 6 inhibitors with deltamethrin showed synergistic effect, and the synergistic effect was most significant when the mixing ratio was 1 : 2. However, no synergistic effect was found when the concentration of deltamethrin was too high.

Conclusion Six potential small molecule inhibitors with insecticidal activity that can stably bind to the Ldmthl1 receptor were obtained through virtual screening. They showed synergistic effects when combined with cypermethrin. This study can lay a theoretical foundation for the development of new insecticides targeting Ldmthl1.