The structures of anthranilate synthase of Serratia marcescens crystallized in the presence of (i) its substrates, chorismate and glutamine, and a product, glutamate, and (ii) its end-product inhibitor, L-tryptophan
The structures of anthranilate synthase of Serratia marcescens crystallized in the presence of (i) its substrates, chorismate and glutamine, and a product, glutamate, and (ii) its end-product inhibitor, L-tryptophan
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DOI：
10.1073/pnas.111150298
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发表时间：
2001-05-22
影响因子：
11.1
通讯作者：
Mills, SE
中科院分区：
文献类型：
--
作者：
Spraggon, G;Kim, C;Mills, SE
来自嗜温细菌粘质沙雷氏菌（Serratia marcescens）的邻氨基苯甲酸合成酶（AS）的晶体结构已在其底物分支酸盐和谷氨酰胺以及一种产物谷氨酸盐（1.95 A）及其结合反馈抑制剂的存在下得到解析。，2.4 W。与来自超嗜热硫化叶菌Sulfolobus solfataricus的AS结构相比，S，marcescens结构显示出相似的亚基结构，但明显不同的寡聚体组织。一种晶型的S。marcescens酶在TrpE亚基中显示结合的丙酮酸盐以及推定的邻氨基苯甲酸盐（氮基团是不明确的）。它还证实了在TrpG亚基中存在共价结合的谷氨酰硫酯中间体。结合色氨酸的形式揭示了抑制剂结合在不同于底物分支酸的位点上，结合色氨酸似乎通过可证明的构象效应防止分支酸结合，并且结构揭示了仅占据两个反馈抑制位点中的一个可以抑制两个TrpE亚基的催化活性。结构中效应物的存在提供了活性位点中一些氨基酸残基的位置的视图。我们的研究结果进行了讨论，在先前描述的AS结构的S，solfataricus，从肠道细菌获得的突变数据，和酶的作用机制。
The crystal structure of anthranilate synthase (AS) from Serratia marcescens, a mesophilic bacterium, has been solved in the presence of its substrates, chorismate and glutamine, and one product, glutamate, at 1.95 A, and with its bound feedback inhibitor, tryptophan, at 2.4 W. In comparison with the AS structure from the hyperthermophile Sulfolobus solfataricus, the S, marcescens structure shows similar subunit structures but a markedly different oligomeric organization. One crystal form of the S. marcescens enzyme displays a bound pyruvate as well as a putative anthranilate (the nitrogen group is ambiguous) in the TrpE subunit, It also confirms the presence of a covalently bound glutamyl thioester intermediate in the TrpG subunit. The tryptophan-bound form reveals that the inhibitor binds at a site distinct from that of the substrate, chorismate, Bound tryptophan appears to prevent chorismate binding by a demonstrable conformational effect, and the structure reveals how occupancy of only one of the two feedback inhibition sites can immobilize the catalytic activity of both TrpE subunits. The presence of effecters in the structure provides a view of the locations of some of the amino acid residues in the active sites. Our findings are discussed in terms of the previously described AS structure of S, solfataricus, mutational data obtained from enteric bacteria, and the enzyme's mechanism of action.