The ribonucleotide reductase system of Lactococcus lactis - Characterization of an nrdEF enzyme and a new electron transport protein
The ribonucleotide reductase system of Lactococcus lactis - Characterization of an nrdEF enzyme and a new electron transport protein
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DOI：
10.1074/jbc.271.15.8779
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发表时间：
1996-04-12
影响因子：
4.8
通讯作者：
Reichard, P
中科院分区：
文献类型：
--
作者：
Jordan, A;Pontis, E;Reichard, P
大肠杆菌含有三种不同的核糖核苷酸还原酶的遗传信息。其中两种（I类酶）分别由nrdAB和nrdEF基因编码，含有酪氨酰自由基，其产生需要氧。NrdAB酶具有生理活性。nrdEF基因的功能尚不清楚。乳酸乳球菌的DNA中含有与nrdDG基因同源的序列，令人惊讶的是，乳酸乳球菌的一个nrdD（-）突变体。乳酸菌在标准厌氧生长条件下生长良好。该突变体的核糖核苷酸还原酶系统由一个NrdEF型酶和一个小的电子传递蛋白组成。编码操纵子含有nrdEF基因和两个开放阅读框，其中一个（nrdH）编码小的电子传递蛋白。E.我们认为需氧Ⅰ类核糖核苷酸还原酶包含两个亚类，一个由nrdAB编码，在大肠杆菌和真核生物中有活性（Ia类），另一个由nrdEF编码，存在于各种微生物中（Ib类）。NrdEF酶利用NrdH蛋白代替NrdAB酶所用的硫氧还蛋白或谷氧还蛋白作为电子转运蛋白。
Escherichia coli contains the genetic information for three separate ribonucleotide reductases. Two of them (class I enzymes), coded by the nrdAB and nrdEF genes, respectively, contain a tyrosyl radical, whose generation requires oxygen, The NrdAB enzyme is physiologically active. The function of the nrdEF gene is not known. The third enzyme (class III), coded by nrdDG, operates during anaerobiosis, The DNA of Lactococcus lactis contains sequences homologous to the nrdDG genes, Surprisingly, an nrdD(-) mutant of L. lactis grew well under standard anaerobic growth conditions. The ribonucleotide reductase system of this mutant was shown to consist of an enzyme of the NrdEF-type and a small electron transport protein, The coding operon contains the nrdEF genes and two open reading frames, one of which (nrdH) codes for the small protein. The same gene organization is present in E. coli, We propose that the aerobic class I ribonucleotide reductases contain two subclasses, one coded by nrdAB, active in E, coli and eukaryotes (class Ia), the other coded by nrdEF, present in various microorganisms (class Ib), The NrdEF enzymes use NrdH proteins as electron transporter in place of thioredoxin or glutaredoxin used by NrdAB enzymes, The two classes also differ in their allosteric regulation by dATP.