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

Abstract：

:Positive selection sites (PSSs), a class of amino acid sites with an excess of nonsynonymous to synonymous substitutions, are indicators of adaptive molecular evolution and have been detected in many protein families involved in a diversity of biological processes by statistical approaches. However, few studies are conducted to evaluate their functional significance and the driving force behind the evolution (i.e., agent of selection). Scorpion α-toxins are a class of multigene family of peptide neurotoxins affecting voltage-gated Na(+ )(Nav) channels, whose members exhibit differential potency and preference for insect and mammalian Nav channels. 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 ((19)AlaPhe(20)) 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 (Ile(40) and Leu(41)) 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.

journal_name

Mol Biol Evol

journal_title

Molecular biology and evolution

authors

Zhu L,Peigneur S,Gao B,Zhang S,Tytgat J,Zhu S

doi

10.1093/molbev/msw065

subject

Has Abstract

pub_date

2016-08-01 00:00:00

pages

1907-20

issue

eissn

0737-4038

issn

1537-1719

pii

msw065

journal_volume

pub_type

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