Orientationally-selected two-dimensional ESEEM spectroscopy of the Rieske-type iron-sulfur cluster in 2,4,5-trichlorophenoxyacetate monooxygenase from Burkholderia cepacia AC1100
Orientationally-selected two-dimensional ESEEM spectroscopy of the Rieske-type iron-sulfur cluster in 2,4,5-trichlorophenoxyacetate monooxygenase from Burkholderia cepacia AC1100
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DOI：
10.1021/ja960781x
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发表时间：
1996-09-04
影响因子：
15
通讯作者：
Bowman, MK
中科院分区：
文献类型：
--
作者：
Dikanov, SA;Xun, LY;Bowman, MK
洋葱伯克霍尔德氏菌AC1100能够利用氯化化合物2，4，5-三氯苯氧基乙酸(2，4，5-T)作为唯一的碳和能源来源。早些时候进行的连续波EPR和一维ESEEM光谱研究表明，洋葱杆菌的2，4，5-T单加氧酶中存在一个Rieske型[2Fe-2S]簇和两个配位的组氨酸残基。本文描述了二维ESEEM谱(称为HYSCORE)在进一步表征还原Rieske型团簇周围的氮原子方面的应用。在g张量主方向附近的场位置测量的HYSCORE谱包含了来自每个组氨酸氮的两个双量子跃迁的交叉峰的主要贡献。这使得可以估计沿g张量主轴的超精细张量的对角分量：4.05、3.88和4.01 MHz(N1)和4.71、5.07和5.02 MHz(N2)。组氨酸氮的其他光谱特征通常强度要弱得多，偶尔会在光谱中观察到。还对脐孔藻铁氧还蛋白中含有四个半胱氨酸配体的还原的[2Fe-2S]植物铁氧还蛋白簇进行了HYSCORE测量，并观察到了由肽氮产生的光谱特征。类似的特征也出现在Rieske星系团的HYSCORE谱中。2，4，5-T单加氧酶与相关苯加氧酶和邻苯二甲酸双加氧酶的结果之间存在系统差异，这可能反映了组氨酸连接和Rieske型[2Fe-2S]簇中邻近氨基酸的氮基的结构和功能上的差异。
Burkholderia cepacia AC1100 is able to use the chlorinated compound 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) as the sole source of carbon and energy. CW EPR and one-dimensional ESEEM spectroscopy studies performed earlier indicate the presence of a Rieske-type [2Fe-2S] cluster with two coordinated histidine residues in 2,4,5-T monooxygenase from B. cepacia. This paper describes the application of two-dimensional ESEEM (called HYSCORE) spectroscopy for further characterization of the nitrogens surrounding the reduced Rieske-type cluster. The HYSCORE spectra measured at field positions in the neighborhood of the principal directions of the g tensor contain major contributions from cross-peaks correlating the two double-quantum transitions from each histidine nitrogen. These allow the estimation of the diagonal components of the hyperfine tensors along the principal axes of the g tensor: 4.05, 3.88, and 4.01 MHz (N1) and 4.71, 5.07, and 5.02 MHz (N2). Other spectral features from the histidine nitrogens usually have a much weaker intensity and are occasionally observed in the spectra. HYSCORE measurements have been also performed with the reduced [2Fe-2S] plant ferredoxin-type cluster with four cysteine ligands in a ferredoxin from Porphira umbilicalis, and spectral features produced by the peptide nitrogen are observed. Similar features also appear in the HYSCORE spectra of the Rieske cluster. Systematic differences are observed between 2,4,5-T monooxygenase and published results from related benzene and phthalate dioxygenases that may reflect structural and functional differences in histidine ligation and the nitrogens of nearby amino acids in Rieske-type [2Fe-2S] clusters.