Crystal structure of the di-iron/radical protein of ribonucleotide reductase from Corynebacterium ammoniagenes
Crystal structure of the di-iron/radical protein of ribonucleotide reductase from Corynebacterium ammoniagenes
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DOI：
10.1021/bi011429l
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发表时间：
2002-01-29
期刊：
影响因子：
2.9
通讯作者：
Nordlund, P
中科院分区：
文献类型：
--
作者：
Högbom, M;Huque, Y;Nordlund, P
核糖核苷酸还原酶 (RNR) 是一种从头生成 DNA 合成所需的四种脱氧核糖核苷酸的酶。所有哺乳动物以及一些原核生物都表达 I 类酶，它是一种 alpha(2)beta(2) 蛋白。较小的同型二聚体，表示为 R2，含有一个二铁羧酸盐位点，在与分子氧反应时，生成催化所需的稳定酪氨酰自由基。来自产氨棒杆菌的氧化类 Ib RNR R2 的三维结构已在 1.85 埃分辨率下测定，并精炼至 R 值 15.8%（R（游离）= 21.3%）。此外，还原的含铁蛋白和锰取代蛋白的结构也已得到解决。产氨梭菌 R2 被认为是锰依赖性的。目前的结构提供了证据，表明锰没有被蛋白质氧化，与最近的生化数据一致，并且在氧化和还原的含铁形式中没有看到明显的结构异常，进一步支持该蛋白质确实是铁依赖性 RNR R2。二锰结构也解释了该位点的磁性。氧化的产氨梭菌 R2 的结构还揭示了桥接自由基和铁位点的额外水分子，这以前在任何其他 R2 结构中都没有见过，并且可能具有重要的机制意义。
Ribonucleotide reductase (RNR) is the enzyme performing de novo production of the four deoxyribonucleotides needed for DNA synthesis. All mammals as well as some prokaryotes express the class I enzyme which is an alpha(2)beta(2) protein. The smaller of the homodimers, denoted R2, contains a di-iron carboxylate site which, upon reaction with molecular oxygen, generates a stable tyrosyl radical needed for catalysis. The three-dimensional structure of the oxidized class Ib RNR R2 from Corynebacterium ammoniagenes has been determined at 1.85 Angstrom resolution and refined to an R-value of 15.8% (R(free) = 21.3%). In addition, structures of both the reduced iron-containing, and manganese-substituted protein have been solved. The C. ammoniagenes R2 has been proposed to be manganese-dependent. The present structure provides evidence that manganese is not oxidized by the protein, in agreement with recent biochemical data, and that no obvious structural abnormalities are seen in the oxidized and reduced iron-containing forms, giving further support that the protein is indeed an iron-dependent RNR R2. The dimanganese structure also provides an explanation for the magnetic properties of this site. The structure of the oxidized C. ammoniagenes R2 also reveals an additional water molecule bridging the radical and the iron site, which has not previously been seen in any other R2 structure and which might have important mechanistic implications.