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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >A previously undescribed pathway for pyrimidine catabolism
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A previously undescribed pathway for pyrimidine catabolism

机译：以前未描述的嘧啶分解代谢途径

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The b1012 operon of Escherichia coli K-12, which is composed of seven unidentified ORFs, is one of the most highly expressed operons under control of nitrogen regulatory protein C. Examination of strains with lesions in this operon on Biolog Phenotype MicroArray (PM3) plates and subsequent growth tests indicated that they failed to use uridine or uracil as the sole nitrogen source and that the parental strain could use them at room temperature but not at 37 degrees C. A strain carrying an ntrB(Con) mutation, which elevates transcription of genes under nitrogen regulatory protein C control, could also grow on thymidine as the sole nitrogen source, whereas strains with lesions in the b1012 operon could not. Growth-yield experiments indicated that both nitrogens of uridine and thymidine were available. Studies with [C-14] uridine indicated that a three-carbon waste product from the pyrimidine ring was excreted. After trimethylsilylation and gas chromatography, the waste product was identified by mass spectrometry as 3-hydroxypropionic acid. In agreement with this finding, 2-methyl-3-hydroxypropionic acid was released from thymidine. Both the number of available nitrogens and the waste products distinguished the pathway encoded by the b1012 operon from pyrimidine catabolic pathways described previously. We propose that the genes of this operon be named rutA-G for pyrimidine utilization. The product of the divergently transcribed gene, b1013, is a tetracycline repressor family regulator that controls transcription of the b1012 operon negatively.
机译：大肠杆菌K-12的b1012操纵子由七个未鉴定的ORF组成，是在氮调节蛋白C的控制下表达最高的操纵子之一。在Biolog表型微阵列（PM3）板上检查该操纵子中有损伤的菌株随后的生长试验表明，他们无法使用尿苷或尿嘧啶作为唯一的氮源，并且亲本菌株可以在室温下但在37摄氏度下不能使用它们。携带ntrB（Con）突变的菌株可以升高转录水平。在氮调节蛋白C控制下的基因也可以在胸苷上作为唯一的氮源生长，而在b1012操纵子中具有损伤的菌株则不能。生长-产量实验表明尿苷和胸苷的氮均可用。用[C-14]尿苷进行的研究表明，从嘧啶环中排出了三碳废物。在三甲基甲硅烷基化和气相色谱法之后，通过质谱将废产物鉴定为3-羟基丙酸。与该发现一致，从胸苷中释放出2-甲基-3-羟基丙酸。可用氮的数量和废物均将b1012操纵子编码的途径与之前描述的嘧啶分解代谢途径区分开来。我们建议将此操纵子的基因命名为rutA-G，用于嘧啶的利用。差异转录的基因b1013的产物是四环素阻遏物家族调节剂，可负性控制b1012操纵子的转录。

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