title: SdPI, the first functionally characterized Kunitz-type trypsin inhibitor from scorpion venom.
abstract: BACKGROUND
  Kunitz-type venom peptides have been isolated from a wide variety of venomous animals. They usually have protease inhibitory activity or potassium channel blocking activity, which by virtue of the effects on predator animals are essential for the survival of venomous animals. However, no Kunitz-type peptides from scorpion venom have been functionally characterized.
  
  
  RESULTS
  A new Kunitz-type venom peptide gene precursor, SdPI, was cloned and characterized from a venom gland cDNA library of the scorpion Lychas mucronatus. It codes for a signal peptide of 21 residues and a mature peptide of 59 residues. The mature SdPI peptide possesses a unique cysteine framework reticulated by three disulfide bridges, different from all reported Kunitz-type proteins. The recombinant SdPI peptide was functionally expressed. It showed trypsin inhibitory activity with high potency (K(i) = 1.6×10(-7) M) and thermostability.
  
  
  CONCLUSIONS
  The results illustrated that SdPI is a potent and stable serine protease inhibitor. Further mutagenesis and molecular dynamics simulation revealed that SdPI possesses a serine protease inhibitory active site similar to other Kunitz-type venom peptides. To our knowledge, SdPI is the first functionally characterized Kunitz-type trypsin inhibitor derived from scorpion venom, and it represents a new class of Kunitz-type venom peptides.
authors.affiliation: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, People's Republic of China.
authors.forename: Ruiming
authors.initials: R
authors.lastname: Zhao
authors.forename: Hui
authors.initials: H
authors.lastname: Dai
authors.forename: Su
authors.initials: S
authors.lastname: Qiu
authors.forename: Tian
authors.initials: T
authors.lastname: Li
authors.forename: Yawen
authors.initials: Y
authors.lastname: He
authors.forename: Yibao
authors.initials: Y
authors.lastname: Ma
authors.forename: Zongyun
authors.initials: Z
authors.lastname: Chen
authors.forename: Yingliang
authors.initials: Y
authors.lastname: Wu
authors.forename: Wenxin
authors.initials: W
authors.lastname: Li
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Cao
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D015723:Gene Library; D055550:Protein Stability; D012604:Scorpion Venoms / Q000737:chemistry*; D015842:Serine Proteinase Inhibitors; D014361:Trypsin Inhibitors / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D012604:Scorpion Venoms; D015842:Serine Proteinase Inhibitors; D014361:Trypsin Inhibitors
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