Raghunathan S, Chandross R J, Kretsinger R H, Allison T J, Penington C J, Rule G S
Department of Biology, University of Virginia, Charlottesville 22908.
J Mol Biol. 1994 May 20;238(5):815-32. doi: 10.1006/jmbi.1994.1336.
The structures of three crystal forms of the class mu human glutathione transferase GSTM2-2 have been determined. X-ray phase information was obtained independently from molecular replacement and from anomalous scattering by a single isomorphous derivative. One crystal form contains a single monomer in the asymmetric unit and has been refined to 1.85 A with an overall R factor of 22.6%. The second form contains a single dimer in the asymmetric unit and has been refined to 3.5 A with an R factor of 20.7%. The third form contains two dimers in the asymmetric unit and has been refined to 3.0 A with an R factor of 25.0%. Although all three crystal forms were grown from solutions that contained glutathione-dinitrobenzene, electron density can only be seen for the glutathione portion of the ligand. The first 202 residues in the seven crystallographically independent monomers of GSTM2-2 are essentially identical in structure. However, heterogeneity in the conformation of the side-chain of Tyr115 is observed in the different monomers. The tertiary structure of residues 1-202 is similar to that of the corresponding region in the class mu isoform of glutathione transferase from rat, GST3-3 (Ji et al. (1992), Biochemistry, 31, 10169-10184). However, significant differences in the conformation of the two enzymes have been observed in the region of the active site that binds hydrophobic substrates. These differences include a 2 A shift in the carboxy terminus of a helix, and significant heterogeneity in the conformation of the last 15 residues of the carboxy terminus. The conformation and degree of disorder of the last 15 residues correlates with the extent of protein-protein contacts within the unit cell.
已确定了μ类人谷胱甘肽转移酶GSTM2-2三种晶体形式的结构。通过分子置换和单个同晶型衍生物的反常散射独立获得了X射线相位信息。一种晶体形式在不对称单元中包含一个单体，已精修至1.85 Å，整体R因子为22.6%。第二种形式在不对称单元中包含一个二聚体，已精修至3.5 Å，R因子为20.7%。第三种形式在不对称单元中包含两个二聚体，已精修至3.0 Å，R因子为25.0%。尽管所有三种晶体形式均从含有谷胱甘肽 - 二硝基苯的溶液中生长，但仅能看到配体谷胱甘肽部分的电子密度。GSTM2-2的七个晶体学独立单体中的前202个残基在结构上基本相同。然而，在不同单体中观察到Tyr115侧链构象的异质性。1-202残基的三级结构与大鼠谷胱甘肽转移酶μ类同工型GST3-3（Ji等人，（1992年），《生物化学》，31卷，10169 - 10184页）中相应区域的结构相似。然而，在结合疏水底物的活性位点区域观察到这两种酶在构象上存在显著差异。这些差异包括一个螺旋羧基末端有2 Å的位移，以及羧基末端最后15个残基构象的显著异质性。最后15个残基的构象和无序程度与晶胞内蛋白质 - 蛋白质接触的程度相关。
