Thiamin biosynthesis in Bacillus subtilis:: Structure of the thiazole synthase/sulfur carrier protein complex
Thiamin biosynthesis in Bacillus subtilis:: Structure of the thiazole synthase/sulfur carrier protein complex
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DOI：
10.1021/bi0488911
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发表时间：
2004-09-21
期刊：
影响因子：
2.9
通讯作者：
Ealick, SE
中科院分区：
文献类型：
--
作者：
Settembre, EC;Dorrestein, PC;Ealick, SE
噻唑合成酶是参与硫胺焦磷酸中噻唑部分形成的关键酶。我们在3.15埃的分辨率下确定了这种酶与硫载体蛋白this复合物的结构。噻唑合酶是一种具有222对称性的四聚体。该单体为（β - α）(8)桶状，与醛缩酶1类、黄素单核苷酸依赖性氧化还原酶和磷酸结合超家族相似。硫载体蛋白（ThiS）是一种结构紧凑的蛋白，其折叠与泛素蛋白相似。该结构使我们能够模拟活性部位的底物，脱氧- d -木醛糖5-磷酸（DXP）。该模型确定了Glu98和Asp182为可能参与催化噻唑形成的新活性位点残基。通过诱变实验研究了这两个残基的功能，证实了这两个残基对噻唑的形成是必需的，并确定了Asp 182是参与噻唑合成酶DXP亚胺C3去质子化的碱基。将ThIS结合表面与泛素表面进行比较，发现了泛素上一个功能未知的保守疏水斑块，可能参与了泛素与其一个结合伙伴之间的复合物形成。
Thiazole synthase is the key enzyme involved in the formation of the thiazole moiety of thiamin pyrophosphate. We have determined the structure of this enzyme in complex with ThiS, the sulfur carrier protein, at 3.15 Angstrom resolution. Thiazole synthase is a tetramer with 222 symmetry. The monomer is a (betaalpha)(8) barrel with similarities to the aldolase class 1 and flavin mononucleotide dependent oxidoreductase and phosphate binding superfamilies. The sulfur carrier protein (ThiS) is a compact protein with a fold similar to that of ubiquitin. The structure allowed us to model the substrate, deoxy-D-xylulose 5-phosphate (DXP), in the active site. This model identified Glu98 and Asp182 as new active site residues likely to be involved in the catalysis of thiazole formation. The function of these residues was probed by mutagenesis experiments, which confirmed that both residues are essential for thiazole formation and identified Asp 182 as the base involved in the deprotonation at C3 of the thiazole synthase DXP imine. Comparison of the ThIS binding surface to the surface of ubiquitin identified a conserved hydrophobic patch of unknown function on ubiquitin that may be involved in complex formation between ubiquitin and one of its binding partners.