title: Accelerated evolution and functional divergence of scorpion short-chain K+ channel toxins after speciation.
abstract: The α-KTx14 subfamily of scorpion toxins is a group of short-chain polypeptides affecting K(+) channels, including five known members which are restrictedly distributed in Mesobuthus martensii. Here, we describe seven new α-KTx14 peptides from M. martensii and its sibling species Mesobuthus eupeus, two of which (termed MarKTX-3 and MeuKTX-1) were chemically synthesized and refolded for structural and functional studies. Electrophysiological recordings of effects of these two peptides on an array of voltage-gated potassium channels revealed that MarKTX-3 was capable of inhibiting five mammalian K(v)1 isoforms (rK(v)1.1-rK(v)1.5) and the Drosophila Shaker channel with low potency whereas MeuKTX-1 lacks such activity. Circular dichroism spectroscopy analysis combined with homology modeling demonstrates that MarKTX-3 and MeuKTX-1 both adopt a similar cysteine-stabilized α-helical and β-sheet fold. Evolutionary analysis indicates accelerated amino acid substitutions in the mature-peptide-encoding regions of orthologous α-KTx14 peptides after speciation, thereby providing evidences for adaptive evolution and functional divergence of this subfamily.
authors: Group of Animal Innate Immunity, State Key Laboratory of Integrated Management of Pest Insects & Rodents, Institute of Zoology, Chinese Academy of Sciences, Chaoyang District, Beijing, China.
authors: Bin
authors: B
authors: Gao
authors: Shunyi
authors: S
authors: Zhu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002942:Circular Dichroism; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000145:classification*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012604:Scorpion Venoms / Q000737:chemistry / Q000145:classification* / Q000235:genetics*; D012605:Scorpions; D017386:Sequence Homology, Amino Acid
chemical_list: D026902:Potassium Channel Blockers; D012604:Scorpion Venoms