Tyrosyl free radical formation in the small subunit of mouse ribonucleotide reductase.
Tyrosyl free radical formation in the small subunit of mouse ribonucleotide reductase.
复制标题
小鼠核糖核苷酸还原酶小亚基中酪氨酰自由基的形成。
DOI：
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发表时间：
1990
影响因子：
4.8
通讯作者：
Lars Thelandern
中科院分区：
文献类型：
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作者：
A. U.S.;Ei;Graham J. Mann;Lars Thelandern
哺乳动物核糖核苷酸还原酶的每个R2亚基含有一对高自旋铁离子和活性所必需的酪氨酰自由基。为了研究酪氨酰自由基形成的机制，亚化学计量量的Fe（II）被添加到重组小鼠R2脱辅基蛋白在严格的厌氧条件下，然后将该溶液暴露于空气中。低温EPR光谱表明，从所产生的酪氨酰自由基的信号与添加的Fe（II）的量相关良好，其中添加的Fe（II）的化学计量为产生1个酪氨酰自由基所需的3 Fe（II）：3 Fe（II）+ P + O2 + Tyr-OH + H+-Fe（III）O2-Fe（III）-P + H2O。+ 提尔+ Fe（III），其中P是蛋白R2的铁结合位点，Tyr-OH是活性酪氨酰残基。假定的中间体O2（2-）-Fe（III）2-P状态的O-O键被Fe（II）提供的额外电子裂解，导致形成OH。其又与Tyr-OH反应得到Tyr-O。在抗坏血酸的存在下，添加以减少形成的单体Fe（III），添加的Fe（II）的80%产生自由基。结果强烈表明，每个二聚体的Fe（III）中心在其形成过程中可以产生酪氨酰自由基和铁结合R2脱辅基蛋白是高度合作。
Each R2 subunit of mammalian ribonucleotide reductase contains a pair of high spin ferric ions and a tyrosyl free radical essential for activity. To study the mechanism of tyrosyl radical formation, substoichiometric amounts of Fe(II) were added to recombinant mouse R2 apoprotein under strictly anaerobic conditions and then the solution was exposed to air. Low temperature EPR spectroscopy showed that the signal from the generated tyrosyl free radical correlated well with the quantity of the Fe(II) added with a stoichiometry of 3 Fe(II) needed to produce 1 tyrosyl radical: 3 Fe(II) + P + O2 + Tyr-OH + H+----Fe(III)O2-Fe(III)-P + H2O. + Tyr-O. + Fe(III), where P is an iron-binding site of protein R2 and Tyr-OH is the active tyrosyl residue. The O-O bond of a postulated intermediate O2(2-)-Fe(III)2-P state is cleaved by the extra electron provided by Fe(II) leading to formation of OH., which in turn reacts with Tyr-OH to give Tyr-O.. In the presence of ascorbate, added to reduce the monomeric Fe(III) formed, 80% of the Fe(II) added produced a radical. The results strongly indicate that each dimeric Fe(III) center during its formation can generate a tyrosyl-free radical and that iron binding to R2 apoprotein is highly cooperative.