精制substrate-bound结构和phosphate-bound thymidylate合成酶干酪乳杆菌。
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佩里Finer-Moore J, Fauman EB,培育PG,公里,桑蒂DV, Stroud RM
精制substrate-bound结构和phosphate-bound thymidylate合成酶干酪乳杆菌。
J杂志。1993年8月20日,232 (4):1101 - 16。
- PubMed ID
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8371269 (在PubMed]
- 文摘
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两种晶体的晶体结构形式复杂的干酪乳杆菌(TS)与衬底转储分辨率2.55已经解决和完善。两个晶体形式c-axis长度相差约5%。TS-dUMP复合物是对称的二聚体与转储等同于在活跃的网站。转储是共价结合在三元复合体的构象的TS转储和代数余子式和代数余子式类似物。相同的TS和衬底之间的氢键是由二元和三元配合物。我们还确定了2.36 phosphate-bound l .干酪乳杆菌TS的晶体结构。这种结构已被提炼与几何高度约束的r因子为19.3%。细化显示位置所有残留的蛋白质,包括无序残留90年到119年,这是一个插入发现只有在l .干酪乳杆菌和金黄色葡萄球菌转座子Tn4003 TS序列。2.9多个同形替换(MIR) l .干酪乳杆菌TS在复杂结构的基质转储被精制结晶r因子为15.5%。减少特工被扣留在米尔从结晶的解决方案结构决心让重金属半胱氨酸残基的标签。因此,这种结构的活性部位半胱氨酸残基氧化和转储是发现half-occupancy活性部位。 No significant conformational difference was found between the phosphate-bound and dUMP-bound structures. The TS-dUMP structures were better ordered than the phosphate-bound TS or the oxidized TS-dUMP, particularly Arg23, which is clearly hydrogen-bonded to the phosphate group of dUMP. A large and a small P6(1)22 crystal form are observed for both phosphate-bound and dUMP-bound L. casei TS. The small cell forms of the phosphate-bound and dUMP-bound enzyme are isomorphous, whereas the cell constants of the larger cell form change slightly when dUMP is bound (c = 240 A versus c = 243 A). For both liganded and unliganded enzyme, conversion from the small to the large crystal form sometimes occurs spontaneously, and the crystal packing changes at a single interface. Conversion may be the result of a small change in pH in the mother liquor surrounding the crystal. A single intermolecular contact between symmetry-related Asp287 residues is disrupted on going from the small to the large crystal form.