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首页> 外文期刊>Biochemistry >Circular Dichroism and Magnetic Circular Dichroism Studies of the Biferrous Form of the R2 Subunit of Ribonucleotide Reductase from Mouse: Comparison to the R2 from Escherichia coli and Other Binuclear Ferrous Enzymes.
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Circular Dichroism and Magnetic Circular Dichroism Studies of the Biferrous Form of the R2 Subunit of Ribonucleotide Reductase from Mouse: Comparison to the R2 from Escherichia coli and Other Binuclear Ferrous Enzymes.

机译：小鼠核糖核苷酸还原酶R2亚基的亚铁形式的圆二色性和磁性圆二色性的研究：与大肠杆菌和其他双核亚铁酶的R2比较。

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Ribonucleotide reductase (RNR) catalyzes the synthesis of the four deoxyribonucleotides needed for DNA synthesis and repair in living organisms. The reduced [Fe(II)Fe(II)] form of the model mammalian enzyme, mouse RNR R2, has been studied using a combination of circular dichroism (CD), magnetic circular dichroism (MCD), and variable-temperature variable-field (VTVH) MCD spectroscopies. Titrations of ferrous ion to the apo-enzyme have been performed and analyzed to investigate the metal binding affinity of the metal-binding site. Spectral features of individual iron sites have been analyzed to obtain detailed geometric and electronic structural information. VTVH MCD data have been collected and analyzed using two complementary models to obtain detailed ground state information including the zero-field splitting (ZFS) of both ferrous centers and the exchange coupling (J) between the two sites. These ground and excited state results provide a complete description of the biferrous site of mouse R2. The biferrous site consists of one 4- and one 5-coordinate iron, with positive and negative ZFS values, respectively. Weak exchange coupling between the two ferrous centers is present, consistent with having carboxylate bridges. The two sites have highly cooperative and weak metal binding affinities. This may be a novel regulatory mechanism for RNR. These results are compared with those from reduced Escherichia coli R2 and reduced acyl-carrier protein Delta(9) desaturase to correlate to similarities and differences in their dioxygen reactivity.
机译：核糖核苷酸还原酶（RNR）催化生物体内DNA合成和修复所需的四个脱氧核糖核苷酸的合成。已使用圆二色性（CD），磁圆二色​​性（MCD）和可变温度可变场的组合研究了模型哺乳动物酶小鼠RNR R2的还原形式[Fe（II）Fe（II）] （VTVH）MCD光谱学。已进行亚铁离子对脱辅酶的滴定和分析，以研究金属结合位点的金属结合亲和力。分析了各个铁站点的光谱特征，以获得详细的几何和电子结构信息。已使用两个互补模型收集并分析了VTVH MCD数据，以获得详细的地面状态信息，包括两个铁心中心的零场分裂（ZFS）和两个站点之间的交换耦合（J）。这些基态和激发态结果提供了对小鼠R2的双金属位点的完整描述。双金属站点由一个4坐标铁和一个5坐标铁组成，ZFS值分别为正值和负值。存在两个亚铁中心之间的弱交换耦合，这与具有羧酸酯桥一致。这两个位点具有高度的合作性和较弱的金属结合亲和力。这可能是RNR的新型调节机制。将这些结果与还原的大肠杆菌R2和还原的酰基载体蛋白Delta（9）去饱和酶的结果进行比较，以关联其双氧反应性的相似性和差异。

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