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首页> 外文期刊>Journal of bacteriology >Mutationally altered ribonucleotide reductase from Escherichia coli: characterization of mutations isolated on multicopy plasmids.
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Mutationally altered ribonucleotide reductase from Escherichia coli: characterization of mutations isolated on multicopy plasmids.

机译：来自大肠杆菌的突变改变的核糖核苷酸还原酶：表征在多拷贝质粒上分离的突变。

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The Escherichia coli ribonucleotide reductase genes (nrd genes) were mutagenized at random. Point mutations were introduced in vitro into a recombinant nrd plasmid. Transformants were initially screened for altered tolerance toward the drug hydroxyurea and further characterized by enzymatic and immunological methods. The screening procedure could pick out defects in either of the two subunits of ribonucleotide reductase. Cells carrying the nrd plasmid pPS2 were earlier shown to have levels of ribonucleotide reductase molecules that were 10 to 20 times higher than those in wild-type cells. We now demonstrate that the enzymatic activity in gently lysed pPS2-containing cells on cellophane disks is six times higher than in wild-type cells. Supplementation of the pPS2-containing lysates with a purified thioredoxin system results in a further 4.5-fold stimulation of the enzymatic activity, which implies a functional shortage of the electron donor system(s) for ribonucleotide reduction in pPS2-containing cells.
机译：随机诱变大肠杆菌核糖核苷酸还原酶基因（nrd基因）。将点突变体外引入重组nrd质粒中。最初针对转化体对药物羟基脲的耐受性进行了筛选，然后通过酶促和免疫学方法对其进行了表征。筛选程序可以挑选出核糖核苷酸还原酶两个亚基中任何一个的缺陷。较早显示携带nrd质粒pPS2的细胞具有的核糖核苷酸还原酶分子水平比野生型细胞高10至20倍。我们现在证明，在玻璃纸盘上轻轻溶解的含pPS2的细胞中的酶活性比野生型细胞高六倍。用纯化的硫氧还蛋白系统补充含pPS2的裂解物会进一步刺激酶活性4.5倍，这意味着电子供体系统功能不足，无法还原含pPS2的细胞中的核糖核苷酸。

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