Target-Driven Positive Selection at Hot Spots of Scorpion Toxins Uncovers Their Potential in Design of Insecticides

In this study, we undertook a systematical molecular dissection of nearly all the PSSs newly characterized in the Mesobuthus α-toxin family and a two-residue insertion (19AlaPhe20) located within a positively selected loop via mutational analysis of α-like MeuNaTxα-5, one member affecting both insect and mammalian Nav channels. This allows to identify hot-spot residues on its functional face involved in interaction with the receptor site of Nav channels, which comprises two PSSs (Ile40 and Leu41) and the small insertion, both located on two spatially separated functional loops. Mutations at these hot-spots resulted in a remarkably decreased anti-mammalian activity in MeuNaTxα-5 with partially impaired or enhanced insecticide activity, suggesting the potential of PSSs in designing promising candidate insecticides from scorpion α-like toxins. Based on an experiment-guided toxin-channel complex model and high evolutionary variability in the receptor site of predators and prey of scorpions, we provide new evidence for target-driven adaptive evolution of scorpion toxins to deal with their targets’ diversity.
Source: Molecular Biology and Evolution - Category: Molecular Biology Authors: Tags: Discoveries Source Type: research