Molecular characterization of a possible progenitor sodium channel toxin from the Old World scorpion Mesobuthus martensii.
Toxins affecting sodium channels widely exist in the venoms of scorpions throughout the world. These molecules comprise an evolutionarily related peptide family with three shared features including conserved three-dimensional structure and gene organization, and similar function. Based on different pharmacological profiles and binding properties, scorpion sodium channel toxins are divided into alpha- and beta-groups. However, their evolutionary relationship is not yet established. Here, we report a gene isolated from the venom gland of scorpion Mesobuthus martensii which encodes a novel sodium channel toxin-like peptide of 64 amino acids, named Mesotoxin. The Mesotoxin gene is organized into three exons and two introns with the second intron location conserved across the family. This peptide is unusual in that it has only three disulfides and a long cysteine-free tail with loop size and structural characteristics close to beta-toxins. Evolutionary analysis favors its basal position in the origin of scorpion sodium channel toxins as a progenitor. The discovery of Mesotoxin will assist investigations into the key issue regarding the origin and evolution of scorpion toxins.
Zhu
S
S
Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, No. 25 Beisihuan-Xi Road, Beijing 100080, PR China. Zhusy@ioz.ac.cn
Gao
B
B
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D011487:Protein Conformation; D012313:RNA / Q000737:chemistry / Q000235:genetics; D012604:Scorpion Venoms / Q000737:chemistry* / Q000235:genetics* / Q000633:toxicity; D012605:Scorpions / Q000737:chemistry* / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000187:drug effects*
D018076:DNA, Complementary; D012604:Scorpion Venoms; D015222:Sodium Channels; D012313:RNA