CRYSTAL-STRUCTURE OF HUMAN CLASS MU-GLUTATHIONE TRANSFERASE GSTM2-2 - EFFECTS OF LATTICE PACKING ON CONFORMATIONAL HETEROGENEITY
CRYSTAL-STRUCTURE OF HUMAN CLASS MU-GLUTATHIONE TRANSFERASE GSTM2-2 - EFFECTS OF LATTICE PACKING ON CONFORMATIONAL HETEROGENEITY
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DOI：
10.1006/jmbi.1994.1336
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发表时间：
1994-05-20
影响因子：
5.6
通讯作者：
RULE, GS
中科院分区：
文献类型：
--
作者：
RAGHUNATHAN, S;CHANDROSS, RJ;RULE, GS
测定了类人谷胱甘肽转移酶GSTM2-2的三种晶型的结构。X射线位相信息的获得独立于分子置换和单个同晶导数的反常散射。一种晶型在不对称单元中只有一个单体，并被提纯到1.85ä，总的R因子为22.6%。第二种形式在不对称单元中含有单一的二聚体，并已被细化到3.5%，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，并已被精炼到3.0ä，R因子为25.0%。虽然这三种晶型都是从含有谷胱甘肽-二硝基苯的溶液中生长出来的，但只能看到配体的谷胱甘肽部分的电子密度。GSTM2-2的7个结晶学独立单体中的前202个残基在结构上基本相同。然而，在不同的单体中，观察到Tyr115侧链构象的不均一性。残基1-202的三级结构类似于大鼠谷胱甘肽转移酶MU类亚型GST3-3(Jiet al.(1992)，BioChemical，31,10169-10184)中相应区域的三级结构。然而，在与疏水底物结合的活性部位区域，观察到两种酶的构象有显著差异。这些差异包括螺旋的羧基末端发生了2？的移动，以及羧基末端的最后15个残基的构象具有显著的异质性。最后15个残基的构象和无序程度与单位细胞内蛋白质-蛋白质接触的程度有关。
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 Å with an overallRfactor of 22·6%. The second form contains a single dimer in the asymmetric unit and has been refined to 3·5% Å with anRfactor of 20·7%. The third form contains two dimers in the asymmetric unit and has been refined to 3·0 Å with anRfactor 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 crystalographically 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 (Jiet 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 Å 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.