Crystal structure of VioE, a key player in the construction of the molecular skeleton of violacein
Crystal structure of VioE, a key player in the construction of the molecular skeleton of violacein
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DOI：
10.1074/jbc.m708109200
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发表时间：
2008-03-07
影响因子：
4.8
通讯作者：
Nagano, Shingo
中科院分区：
文献类型：
--
作者：
Hirano, Satoshi;Asamizu, Shumpei;Nagano, Shingo
紫罗兰素和吲哚咔唑是天然存在的双吲哚产物，具有多种生物活性，包括抗肿瘤活性。虽然这些化合物具有明显不同的分子骨架，但它们的生物合成途径共享相同的中间“化合物X”，它是由l -色氨酸通过吲哚-3-丙酮酸亚胺产生的。化合物X是一种寿命较短的中间体，可自发转化为吲哚咔唑生物合成的铬吡咯酸，而VioE将化合物X转化为原脱氧堇菜酸，经其他酶进一步修饰生成堇菜素。因此，VioE在violacein分子骨架的构建中起着关键作用。在这里，我们展示了VioE的晶体结构，它由两个亚基组成，每个亚基形成一个类似棒球手套的结构。每个亚基在结构的凹表面的中心有一个带正电的口袋。对表面袋和其他表面残基的诱变分析表明，表面袋是一个活性位点。我们还解决了VioE和苯基丙酮酸的配合物的晶体结构，作为VioE-底物配合物的类似物。与VioE和IPA亚胺二聚体（被认为是化合物X）的对接模拟结果与突变分析结果和VioE-苯基丙酮酸配合物结构一致。基于这些结果，我们提出VioE将高活性的底物捕获在表面袋内，以抑制CPA的形成，并促进由邻近效应和取向效应引起的原脱氧堇菜酸的形成。
Violacein and the indolocarbazoles are naturally occurring bisindole products with various biological activities, including antitumor activity. Although these compounds have markedly different molecular skeletons, their biosynthetic pathways share the same intermediate "compound X," which is produced from L-tryptophan via indole-3-pyruvic acid imine. Compound X is a short-lived intermediate that is spontaneously converted to chromopyrrolic acid for indolocarbazole biosynthesis, whereas VioE transforms compound X into protodeoxyviolaceinic acid, which is further modified by other enzymes to produce violacein. Thus, VioE plays a key role in the construction of the molecular skeleton of violacein. Here, we present the crystal structure of VioE, which consists of two subunits, each of which forms a structure resembling a baseball glove. Each subunit has a positively charged pocket at the center of the concave surface of the structure. Mutagenesis analysis of the surface pocket and other surface residues showed that the surface pocket serves as an active site. We have also solved the crystal structure of a complex of VioE and phenylpyruvic acid as an analogue of a VioE-substrate complex. A docking simulation with VioE and the IPA imine dimer, which is proposed to be compound X, agreed with the results from the mutational analysis and the VioE-phenylpyruvic acid complex structure. Based on these results, we propose that VioE traps the highly reactive substrate within the surface pocket to suppress CPA formation and promote protodeoxyviolaceinic acid formation caused by proximity and orientation effects.