A manganese(IV)/iron(IV) intermediate in assembly of the manganese(IV)/iron(III) cofactor of Chlamydia trachomatis ribonucleotide reductase
A manganese(IV)/iron(IV) intermediate in assembly of the manganese(IV)/iron(III) cofactor of Chlamydia trachomatis ribonucleotide reductase
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DOI：
10.1021/bi700906g
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发表时间：
2007-07-31
期刊：
影响因子：
2.9
通讯作者：
Martin Bollinger, J., Jr.
中科院分区：
文献类型：
--
作者：
Jiang, Wei;Hoffart, Lee M.;Martin Bollinger, J., Jr.
我们最近表明，来自人类病原体沙眼衣原体的Ic类核糖核苷酸还原酶在其催化机制中使用Mn-IV/Fe-III辅因子来产生蛋白质和底物自由基[Jiang，W.，Yun，D.，萨利赫湖巴尔，E. W.，Xing，G.，霍法特湖M.，Maslak，M.一、克雷布斯角，和Bollinger，J.M.，Jr.（2007）Science 316，1188 - 1191]。在这里，我们已经解剖了这种新的异双核氧化还原辅因子从锰-II/铁-II簇和O-2的形成机制。具有g = 2 EPR信号的中间体显示与Mn-55和Fe-57的超精细耦合几乎定量地在O-2和还原的R2络合物之间的二级反应中积累。否则缓慢衰减的中间体的活性Mn-IV/Fe-III-R2复合物的存在下，加速的单电子还原剂，抗坏血酸，这意味着该中间体是更多的氧化比Mn-IV/Fe-III。穆斯堡尔谱表明中间体含有一个高自旋的Fe-IV中心。其化学和光谱性质表明该中间体是Mn-IV/Fe-IV-R_2配合物，其电子基态S =（1）/（2）是由Mn-IV（S-Mn =（3）/（2））和高自旋Fe-IV（S-Fe = 2）位之间的反铁磁耦合产生的。
We recently showed that the class Ic ribonucleotide reductase from the human pathogen Chlamydia trachomatis uses a Mn-IV/Fe-III cofactor to generate protein and substrate radicals in its catalytic mechanism [Jiang, W., Yun, D., Saleh, L., Barr, E. W., Xing, G., Hoffart, L. M., Maslak, M.-A., Krebs, C., and Bollinger, J. M., Jr. (2007) Science 316, 1188-1191]. Here, we have dissected the mechanism of formation of this novel heterobinuclear redox cofactor from the Mn-II/Fe-II cluster and O-2. An intermediate with a g = 2 EPR signal that shows hyperfine coupling to both Mn-55 and Fe-57 accumulates almost quantitatively in a second-order reaction between O-2 and the reduced R2 complex. The otherwise slow decay of the intermediate to the active Mn-IV/Fe-III-R2 complex is accelerated by the presence of the one-electron reductant, ascorbate, implying that the intermediate is more oxidized than Mn-IV/Fe-III. Mossbauer spectra show that the intermediate contains a high-spin Fe-IV center. Its chemical and spectroscopic properties establish that the intermediate is a Mn-IV/Fe-IV-R2 complex with an S = (1)/(2) electronic ground state arising from antiferromagnetic coupling between the Mn-IV (S-Mn = (3)/(2)) and high-spin Fe-IV (S-Fe = 2) sites.