Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran, Tehran, Iran.
Department of Cell and Molecular Biology, School of Biology, College of Science, University of Tehran, Tehran, Iran.
Arch Biochem Biophys. 2019 Feb 15;662:1-6. doi: 10.1016/j.abb.2018.11.017. Epub 2018 Nov 16.
A new member of kunitz-type protein family, PPTI (PseudocerastesPersicusTrypsin Inhibitor), was isolated from the venom of Persian false horned viper Pseudocerastes persicus and characterized. Mass spectrometry and amino acid sequencing revealed that PPTI is a 68 amino acid protein with molecular weight of about 7.6 kDa. The first amino acid residue of PPTI is N-terminally blocked via a post translational modification to pyroglutamyl. Sequence comparison against UniProtKB shows a high sequence similarity of PPTI with kunitz-type proteins, especially serine protease inhibitors and dendrotoxins (DTXs). The number of cysteines and disulfide bonding pattern of PPTI are the same as kunitz-type proteins. Based on sequence derive information, anti-protease activity of PPTI against trypsin was experimentally examined. The constructed homology models of PPTI confirmed the ability of PPTI to fold similarly to kunitz domain. The presence of characteristic basic-hydrophobic functional dyad of DTXs in PPTI supports its inhibitory potential against potassium channels. In summary, this study hypothesized the dual functionality of PPTI according to its inhibitory effect on trypsin and its potential ability in blocking potassium channel.
从波斯假蝰蛇（Pseudocerastes persicus）的毒液中分离得到了一种新的 Kunitz 型蛋白家族成员 PPTI（Pseudocerastes persicus 胰蛋白酶抑制剂），并对其进行了表征。质谱和氨基酸测序结果表明，PPTI 是一种 68 个氨基酸的蛋白，分子量约为 7.6 kDa。PPTI 的第一个氨基酸残基通过翻译后修饰被 N 端封闭为焦谷氨酸。与 UniProtKB 的序列比较显示，PPTI 与 Kunitz 型蛋白，特别是丝氨酸蛋白酶抑制剂和树眼镜蛇毒素（DTXs）具有高度的序列相似性。PPTI 的半胱氨酸数量和二硫键模式与 Kunitz 型蛋白相同。基于序列推导信息，实验检测了 PPTI 对胰蛋白酶的抗蛋白酶活性。构建的 PPTI 同源模型证实了 PPTI 折叠能力类似于 Kunitz 结构域。PPTI 中存在 DTXs 的特征碱性疏水性功能二联体，支持其对钾通道的抑制潜力。总之，本研究根据 PPTI 对胰蛋白酶的抑制作用及其阻断钾通道的潜在能力，假设其具有双重功能。
