title: Adaptive evolution of insect selective excitatory β-type sodium channel neurotoxins from scorpion venom.
abstract: Insect selective excitatory β-type sodium channel neurotoxins from scorpion venom (β-NaScTxs) are composed of about 70-76 amino acid residues and share a common scaffold stabilized by four unique disulfide bonds. The phylogenetic analysis of these toxins was hindered by limited sequence data. In our recent study, two new insect selective excitatory β-NaScTxs, LmIT and ImIT, were isolated from Lychas mucronatus and Isometrus maculatus, respectively. With the sequences previously reported, we examined the adaptive molecular evolution of insect selective excitatory β-NaScTxs by estimating the nonsynonymous-to-synonymous rate ratio (ω=dN/dS). The results revealed 12 positively selected sites in the genes of insect selective excitatory β-NaScTxs. Moreover, these positively selected sites match well with the sites important for interacting with sodium channels, as demonstrated in previous mutagenesis study. These results reveal that adaptive evolution after gene duplication is one of the most important genetic mechanisms of scorpion neurotoxin diversification.
authors.affiliation: Medical School, Henan University of Science and Technology, Luoyang, Henan Province, PR China. Electronic address: whenas@haust.edu.cn.
authors.forename: Wenlan
authors.initials: W
authors.lastname: Wu
authors.affiliation: Medical School, Henan University of Science and Technology, Luoyang, Henan Province, PR China.
authors.forename: Zhongjie
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine, Richmond, VA, USA. Electronic address: mayibao@163.com.
authors.forename: Yibao
authors.initials: Y
authors.lastname: Ma
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019143:Evolution, Molecular; D015723:Gene Library; D009498:Neurotoxins / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D010802:Phylogeny; D012604:Scorpion Venoms / Q000737:chemistry / Q000145:classification / Q000235:genetics*; D012605:Scorpions / Q000235:genetics*; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D015222:Sodium Channels / Q000737:chemistry / Q000145:classification / Q000235:genetics*
chemical_list: D009498:Neurotoxins; D012604:Scorpion Venoms; D015222:Sodium Channels
keywords: Adaptive evolution; Insect selective excitatory β-NaScTxs; Molecular phylogeny; Scorpion neurotoxins