title: Genomic and structural characterization of Kunitz-type peptide LmKTT-1a highlights diversity and evolution of scorpion potassium channel toxins.
abstract: BACKGROUND
  Recently, a new subfamily of long-chain toxins with a Kunitz-type fold was found in scorpion venom glands. Functionally, these toxins inhibit protease activity and block potassium channels. However, the genomic organization and three-dimensional (3-D) structure of this kind of scorpion toxin has not been reported.
  
  
  RESULTS
  Here, we characterized the genomic organization and 3-D nuclear magnetic resonance structure of the scorpion Kunitz-type toxin, LmKTT-1a, which has a unique cysteine pattern. The LmKTT-1a gene contained three exons, which were interrupted by two introns located in the mature peptide region. Despite little similarity to other Kunitz-type toxins and a unique pattern of disulfide bridges, LmKTT-1a possessed a conserved Kunitz-type structural fold with one α-helix and two β-sheets. Comparison of the genomic organization, 3-D structure, and functional data of known toxins from the α-KTx, β-KTx, γ-KTx, and κ-KTx subfamily suggested that scorpion Kunitz-type potassium channel toxins might have evolved from a new ancestor that is completely different from the common ancestor of scorpion toxins with a CSα/β fold. Thus, these analyses provide evidence of a new scorpion potassium channel toxin subfamily, which we have named δ-KTx.
  
  
  CONCLUSIONS
  Our results highlight the genomic, structural, and evolutionary diversity of scorpion potassium channel toxins. These findings may accelerate the design and development of diagnostic and therapeutic peptide agents for human potassium channelopathies.
authors.affiliation: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, PR China.
authors.forename: Zongyun
authors.initials: Z
authors.lastname: Chen
authors.forename: Fan
authors.initials: F
authors.lastname: Luo
authors.forename: Jing
authors.initials: J
authors.lastname: Feng
authors.forename: Weishan
authors.initials: W
authors.lastname: Yang
authors.forename: Danyun
authors.initials: D
authors.lastname: Zeng
authors.forename: Ruiming
authors.initials: R
authors.lastname: Zhao
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Cao
authors.forename: Maili
authors.initials: M
authors.lastname: Liu
authors.forename: Wenxin
authors.initials: W
authors.lastname: Li
authors.forename: Ling
authors.initials: L
authors.lastname: Jiang
authors.forename: Yingliang
authors.initials: Y
authors.lastname: Wu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D060829:Arthropod Proteins / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D001483:Base Sequence; D003553:Cystine / Q000737:chemistry; D057809:HEK293 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D051664:Kv1.3 Potassium Channel / Q000037:antagonists & inhibitors / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D026902:Potassium Channel Blockers / Q000737:chemistry* / Q000494:pharmacology; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012604:Scorpion Venoms / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology; D012605:Scorpions / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014357:Trypsin / Q000737:chemistry; D014361:Trypsin Inhibitors / Q000737:chemistry / Q000235:genetics
chemical_list: D060829:Arthropod Proteins; D051664:Kv1.3 Potassium Channel; D026902:Potassium Channel Blockers; D012604:Scorpion Venoms; D014361:Trypsin Inhibitors; D003553:Cystine; D014357:Trypsin