Gáspári Zoltán, Szenthe Borbála, Patthy András, Westler William M, Gráf László, Perczel András
Institute of Chemistry, Eötvös Loránd University, Budapest, Hungary.
FEBS J. 2006 Apr;273(8):1831-42. doi: 10.1111/j.1742-4658.2006.05204.x.
Complexation of the small serine protease inhibitor Schistocerca gregaria chymotrypsin inhibitor (SGCI), a member of the pacifastin inhibitor family, with bovine chymotrypsin was followed by NMR spectroscopy. (1)H-(15)N correlation (HSQC) spectra of the inhibitor with increasing amounts of the enzyme reveal tight and specific binding in agreement with biochemical data. Unexpectedly, and unparalleled among canonical serine protease inhibitors, not only residues in the protease-binding loop of the inhibitor, but also some segments of it located spatially far from the substrate-binding cleft of the enzyme were affected by complexation. However, besides changes, some of the dynamical features of the free inhibitor are retained in the complex. Comparison of the free and complexed inhibitor structures revealed that most, but not all, of the observed chemical shift changes can be attributed to minor structural transitions. We suggest that the classical 'scaffold + binding loop' model of canonical inhibitors might not be fully valid for the inhibitor family studied. In our view, this feature allows for the emergence of both taxon-specific and nontaxon-specific inhibitors in this group of small proteins.
作为太平洋丝氨酸蛋白酶抑制剂家族的一员，小型丝氨酸蛋白酶抑制剂——沙漠蝗胰凝乳蛋白酶抑制剂（SGCI）与牛胰凝乳蛋白酶的络合过程通过核磁共振光谱进行跟踪。随着酶量的增加，抑制剂的氢-氮相关（HSQC）光谱显示出紧密且特异性的结合，这与生化数据一致。出乎意料的是，在典型丝氨酸蛋白酶抑制剂中独一无二的是，不仅抑制剂的蛋白酶结合环中的残基，而且其在空间上远离酶底物结合裂隙的一些片段也受到络合的影响。然而，除了变化之外，游离抑制剂的一些动力学特征在络合物中得以保留。游离和络合抑制剂结构的比较表明，观察到的化学位移变化中的大多数（但不是全部）可归因于微小的结构转变。我们认为，典型抑制剂的经典“支架+结合环”模型可能对所研究的抑制剂家族并不完全适用。我们认为，这一特征使得在这组小蛋白质中既出现了分类群特异性抑制剂，也出现了非分类群特异性抑制剂。
