Bailey S, Smith K, Fairlamb A H, Hunter W N
Department of Chemistry, University of Manchester, England.
Eur J Biochem. 1993 Apr 1;213(1):67-75. doi: 10.1111/j.1432-1033.1993.tb17734.x.
The enzyme trypanothione reductase has been identified as a prime target for the rational design of inhibitors which may have clinical use in the treatment of tropical diseases caused by the genera Trypanosoma and Leishmania. To aid the design or identification of new inhibitors of this enzyme we have elucidated the structural detail of a trypanothione reductase complexed with one of the naturally occurring substrates, N1-glutathionylspermidine disulphide, by single-crystal X-ray diffraction methods at 0.28-nm resolution. The model for the Crithidia fasciculata enzyme-substrate complex has an R-factor of 14.8% and root-mean-square deviations of 0.0015 nm and 3.3 degrees on bond lengths and angles respectively. Hydrogen bonding and van der Waals interactions between the enzyme and substrate are dominated by the amino acid side chains. The substrate binds in a rigid active site such that one glutathione moiety is in a V-shape, the other in an extended conformation. One spermidine moiety binds closely to a hydrophobic patch in the active site formed by a tryptophan and a methionine. Distances between the methionine S delta and the terminal N of this spermidine suggest that a hydrogen bond may supplement the hydrophobic interactions in this part of the active site.
已确定锥虫硫醇还原酶是合理设计抑制剂的主要靶点，这些抑制剂可能在治疗由锥虫属和利什曼原虫属引起的热带疾病中具有临床应用价值。为了辅助设计或鉴定该酶的新型抑制剂，我们通过分辨率为0.28纳米的单晶X射线衍射方法，阐明了与一种天然存在的底物N1-谷胱甘肽亚精胺二硫化物复合的锥虫硫醇还原酶的结构细节。克氏锥虫酶-底物复合物的模型R因子为14.8%，键长和键角的均方根偏差分别为0.0015纳米和3.3度。酶与底物之间的氢键和范德华相互作用主要由氨基酸侧链主导。底物结合在一个刚性活性位点上，使得一个谷胱甘肽部分呈V形，另一个呈伸展构象。一个亚精胺部分紧密结合到由一个色氨酸和一个甲硫氨酸形成的活性位点中的疏水区域。甲硫氨酸Sδ与该亚精胺末端N之间的距离表明，氢键可能会补充该活性位点这一部分的疏水相互作用。
