title: Functional characterization of a new non-Kunitz serine protease inhibitor from the scorpion Lychas mucronatus.
abstract: Serine protease inhibitors have been widely discovered from different animal venoms, but most of them belong to Kunitz-type toxin subfamily. Here, by screening scorpion venom gland cDNA libraries, we identified four new non-Kunitz serine protease inhibitors with a conserved Ascaris-type structural fold: Ascaris-type toxins Lychas mucronatus Ascaris-type protease inhibitor (LmAPI), Pandinus cavimanus Ascaris-type protease inhibitor (PcAPI), Pandinus cavimanus Ascaris-type protease inhibitor 2 (PcAPI-2), and Hottentotta judaicus Ascaris-type protease inhibitor (HjAPI). The detailed characterization of one Ascaris-type toxin LmAPI was further carried out, which contains 60 residues and possesses a classical Ascaris-type cysteine framework reticulated by five disulfide bridges. Enzyme and inhibitor reaction kinetics experiments showed that recombinant LmAPI inhibits the activity of chymotrypsin potently with a Ki value of 15.5 nM, but has little effect on trypsin and elastase. Bioinformatics analyses suggested that LmAPI contains unique functional residues "TQD" and might be a useful template to produce specific protease inhibitors. Our results indicated that animal venoms are a natural source of new type of protease inhibitors, which will accelerate the development of diagnostic and therapeutic agents for human diseases that target diverse proteases.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medicinal Macromolecular Laboratory, School of Basic Medical Sciences, Hubei University of Medicine, Hubei, China.
authors.forename: Hongyan
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Biochemistry and Molecular Biology, Medicinal Macromolecular Laboratory, School of Basic Medical Sciences, Hubei University of Medicine, Hubei, China.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Biochemistry and Molecular Biology, Medicinal Macromolecular Laboratory, School of Basic Medical Sciences, Hubei University of Medicine, Hubei, China.
authors.forename: Shirong
authors.initials: S
authors.lastname: Yan
authors.affiliation: Department of Biochemistry and Molecular Biology, Medicinal Macromolecular Laboratory, School of Basic Medical Sciences, Hubei University of Medicine, Hubei, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Department of Biochemistry and Molecular Biology, Medicinal Macromolecular Laboratory, School of Basic Medical Sciences, Hubei University of Medicine, Hubei, China.
authors.forename: Mingkui
authors.initials: M
authors.lastname: San
authors.affiliation: Department of Biochemistry and Molecular Biology, Medicinal Macromolecular Laboratory, School of Basic Medical Sciences, Hubei University of Medicine, Hubei, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China.
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China.
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China.
authors.forename: Wenxin
authors.initials: W
authors.lastname: Li
authors.affiliation: State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Hubei, China.
authors.forename: Yingliang
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Biochemistry and Molecular Biology, Medicinal Macromolecular Laboratory, School of Basic Medical Sciences, Hubei University of Medicine, Hubei, China. Electronic address: zychen@whu.edu.cn.
authors.forename: Zongyun
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015723:Gene Library; D006801:Humans; D011487:Protein Conformation; D017510:Protein Folding; D012604:Scorpion Venoms / Q000737:chemistry*; D012605:Scorpions / Q000737:chemistry*; D016415:Sequence Alignment; D015842:Serine Proteinase Inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D012604:Scorpion Venoms; D015842:Serine Proteinase Inhibitors
keywords: Ascaris-type toxin; Molecular diversity; cDNA libraries