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首页> 外文期刊>Biochemistry >Structure of Salmonella typhimurium nrdF ribonucleotide reductase in its oxidized and reduced forms
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Structure of Salmonella typhimurium nrdF ribonucleotide reductase in its oxidized and reduced forms

机译：鼠伤寒沙门氏菌nrdF核糖核苷酸还原酶的结构

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The first class Tt,ribonucleotide reductase R2 structure, from Salmonella typhimurium, has been determined at 2.0 Angstrom resolution. The overall structure is similar to the Escherichia coli class Ia enzyme despite only 23% sequence identity. The most spectacular difference is the absence of the pleated sheet and adjacent parts present in the E. coli R2 structure; the heart-shaped structure loses its tip. From sequence comparisons, it appears that this feature is shared with all other class To enzymes and, in this respect, is more like the mammalian class Ia enzymes. Both the oxidized and reduced iron forms have been investigated. In the ferric iron center, both iron ions are octahedrally coordinated and bridged by one carboxylate and one oxide ion. The ferrous form has lost the bridging oxide ion but is bridged by two carboxylates. Accompanying the change in redox state, helix E changes its conformation from one covering the metal center in the oxidized form to a more open reduced form. A narrow channel is opened which may permit easier access of oxygen to the ferrous iron site and to efficiently generate the tyrosyl radical. [References: 63]
机译：来自鼠伤寒沙门氏菌的第一类Tt，核糖核苷酸还原酶R2结构已在2.0埃分辨率下确定。尽管只有23％的序列同一性，但总体结构与大肠杆菌Ia类酶相似。最引人注目的区别是大肠杆菌R2结构中不存在褶皱片和相邻部件。心形结构失去了尖端。从序列比较中，似乎该特征与所有其他To类酶共享，并且在这一方面，它更像哺乳动物的Ia类酶。已经研究了氧化和还原的铁形式。在三价铁中心，两个铁离子都是八面体配位并由一个羧酸根和一个氧化物离子桥接。亚铁形式已经失去了桥接的氧离子，但被两个羧酸盐桥接。伴随着氧化还原状态的变化，螺旋E的构象从一个以氧化形式覆盖金属中心的构象改变为更开放的还原形式。打开狭窄的通道，这可以使氧气更容易进入亚铁部位并有效地产生酪氨酰基。 [参考：63]

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