Structural insights into the mechanism for recognizing substrate of the cytochrome P450 enzyme TxtE.
Structural insights into the mechanism for recognizing substrate of the cytochrome P450 enzyme TxtE.
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细胞色素 P450 酶 TxtE 底物识别机制的结构见解
DOI：
10.1371/journal.pone.0081526
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发表时间：
2013
期刊：
影响因子：
3.7
通讯作者：
He J
中科院分区：
文献类型：
--
作者：
Yu F;Li M;Xu C;Wang Z;Zhou H;Yang M;Chen Y;Tang L;He J
Thaxtomins是链霉菌产生的一种植物毒素，可引起植物细胞肥大和幼苗发育迟缓。Thaxtomin A是疥疮链霉菌的主要形式，并已证明具有除草作用。TxtE是一种来自疥疮链霉菌87.22的细胞色素P450酶，它利用一氧化氮、二氧和NADPH催化l -色氨酸的吲哚基部分直接硝化为l -4-硝基色氨酸。在2.1 Å分辨率下测定了TxtE的晶体结构，并在本工作中进行了描述。观察到一个明确定义的底物进入通道，可归类为通道2a，这在细菌细胞色素P450酶中很常见。观察到从活性位点到外部溶剂的连续氢键链。与其他细胞色素P450酶相比，TxtE具有独特的质子转移途径，可以穿过螺旋I畸变。通过分子对接分析发现Arg59、Tyr89、Asn293、Thr296和Glu394与l -色氨酸的极性接触，这对底物识别和结合具有潜在的重要意义。将Arg59、Asn293、Thr296或Glu394突变为亮氨酸后，TxtE的底物结合能力明显丧失或降低。基于对接和突变的结果，提出了一种可能的底物识别和结合机制。
Thaxtomins, a family of phytotoxins produced by Streptomyces spp., can cause dramatic plant cell hypertrophy and seedling stunting. Thaxtomin A is the dominant form from Streptomyces scabies and has demonstrated herbicidal action. TxtE, a cytochrome P450 enzyme from Streptomyces scabies 87.22, catalyzes direct nitration of the indolyl moiety of L-tryptophan to L-4-nitrotryptophan using nitric oxide, dioxygen and NADPH. The crystal structure of TxtE was determined at 2.1 Å resolution and described in this work. A clearly defined substrate access channel is observed and can be classified as channel 2a, which is common in bacteria cytochrome P450 enzymes. A continuous hydrogen bond chain from the active site to the external solvent is observed. Compared with other cytochrome P450 enzymes, TxtE shows a unique proton transfer pathway which crosses the helix I distortion. Polar contacts of Arg59, Tyr89, Asn293, Thr296, and Glu394 with L-tryptophan are seen using molecular docking analysis, which are potentially important for substrate recognition and binding. After mutating Arg59, Asn293, Thr296 or Glu394 to leucine, the substrate binding ability of TxtE was lost or decreased significantly. Based on the docking and mutation results, a possible mechanism for substrate recognition and binding is proposed.
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影响因子：
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作者：
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DOI：
10.1073/pnas.0805983105
发表时间：
2008-10-14
影响因子：
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作者：
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通讯作者：
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发表时间：
2004-07-01
期刊：
EUROPEAN JOURNAL OF BIOCHEMISTRY
影响因子：
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作者：
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