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首页> 外文期刊>Biochemistry >Crystal structure of the di-iron/radical protein of ribonucleotide reductase from corynebacterium ammoniagenes
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Crystal structure of the di-iron/radical protein of ribonucleotide reductase from corynebacterium ammoniagenes

机译：产氨棒杆菌的核糖核苷酸还原酶二铁/自由基蛋白的晶体结构

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摘要

Ribonucleotide reductase (RNR) is the enzyme performing do novo production of the four deoxyribonucleotides needed for DNA synthesis. All mammals as well 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 A 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 have 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 propertis 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.
机译：核糖核苷酸还原酶（RNR）是从头生产DNA合成所需的四个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，该酶是＃alpha＃_2＃beta＃_2蛋白。较小的同二聚体，表示为R2，含有二铁羧酸酯位点，该二铁羧酸酯位点在与分子氧反应后会生成催化所需的稳定的酪氨酰基。来自产氨棒杆菌的氧化的Ib RNR R2 R3的三维结构已在1.85 A的分辨率下确定，并精炼至R值为15.8％（R_（游离）= 21.3％）。另外，还解决了还原的含铁蛋白质和锰取代蛋白质的结构。提出了C.ammoniagenes R2是锰依赖性的。目前的结构提供了证据，表明锰并未被蛋白质氧化，这与最近的生化数据相符，并且在氧化和还原的含铁形式中未发现明显的结构异常，进一步证明了蛋白质确实是铁。从属RNR R2。二锰结构也为该部位的磁性体提供了解释。氧化的产氨梭菌R2的结构还揭示了一个桥接自由基和铁位点的水分子，这在任何其他R2结构中都未见过，并且可能具有重要的机理意义。

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