Ali Syed Abid, Alam Mehtab, Abbasi Atiya, Undheim Eivind A B, Fry Bryan Grieg, Kalbacher Hubert, Voelter Wolfgang
International Center for Chemical and Biochemical Sciences (ICCBS), HEJ Research Institute of Chemistry, University of Karachi, Karachi-75270, Pakistan.
Interfaculty Institute of Biochemistry (IIB), University of Tuebingen, Hoppe-Seyler Str. 4, Tuebingen D-72076, Germany.
Toxins (Basel). 2016 Feb 2;8(2):36. doi: 10.3390/toxins8020036.
Animal venom (e.g., scorpion) is a rich source of various protein and peptide toxins with diverse physio-/pharmaco-logical activities, which generally exert their action via target-specific modulation of different ion channel functions. Scorpion venoms are among the most widely-known source of peptidyl neurotoxins used for callipering different ion channels, such as; Na⁺, K⁺, Ca⁺, Cl(-), etc. A new peptide of the chlorotoxin family (i.e., Bs-Tx7) has been isolated, sequenced and synthesized from scorpion Buthus sindicus (family Buthidae) venom. This peptide demonstrates 66% with chlorotoxin (ClTx) and 82% with CFTR channel inhibitor (GaTx1) sequence identities reported from Leiurus quinquestriatus hebraeus venom. The toxin has a molecular mass of 3821 Da and possesses four intra-chain disulphide bonds. Amino acid sequence analysis of Bs-Tx7 revealed the presence of a scissile peptide bond (i.e., Gly-Ile) for human MMP2, whose activity is increased in the case of tumour malignancy. The effect of hMMP2 on Bs-Tx7, or vice versa, observed using the FRET peptide substrate with methoxycoumarin (Mca)/dinitrophenyl (Dnp) as fluorophore/quencher, designed and synthesized to obtain the lowest Km value for this substrate, showed approximately a 60% increase in the activity of hMMP2 upon incubation of Bs-Tx7 with the enzyme at a micromolar concentration (4 µM), indicating the importance of this toxin in diseases associated with decreased MMP2 activity.
动物毒液（如蝎子毒液）富含各种具有不同生理/药理活性的蛋白质和肽类毒素，这些毒素通常通过对不同离子通道功能的靶向特异性调节来发挥作用。蝎子毒液是用于鉴别不同离子通道（如Na⁺、K⁺、Ca⁺、Cl⁻等）的肽类神经毒素最广为人知的来源之一。一种来自蝎子（钳蝎科）毒液的氯毒素家族新肽（即Bs-Tx7）已被分离、测序并合成。该肽与来自以色列金蝎毒液的氯毒素（ClTx）有66%的序列一致性，与CFTR通道抑制剂（GaTx1）有82%的序列一致性。该毒素分子量为3821 Da，具有四个链内二硫键。Bs-Tx7的氨基酸序列分析显示存在人基质金属蛋白酶2（MMP2）的一个可裂解肽键（即甘氨酸-异亮氨酸），在肿瘤恶性程度增加的情况下其活性会增强。使用以甲氧基香豆素（Mca）/二硝基苯基（Dnp）作为荧光团/猝灭剂设计合成的FRET肽底物来观察hMMP2对Bs-Tx7的作用，反之亦然，该底物设计用于获得最低的Km值，结果显示在微摩尔浓度（4 μM）下将Bs-Tx7与该酶孵育后，hMMP2的活性大约增加了60%，这表明该毒素在与MMP2活性降低相关的疾病中的重要性。
