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首页> 外文期刊>Journal of bacteriology >Apparent involvement of purines in the control of expression of Salmonella typhimurium pyr genes: analysis of a leaky guaB mutant resistant to pyrimidine analogs.
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Apparent involvement of purines in the control of expression of Salmonella typhimurium pyr genes: analysis of a leaky guaB mutant resistant to pyrimidine analogs.

机译：嘌呤明显参与了鼠伤寒沙门氏菌pyr基因的表达控制：对嘧啶类似物有抗性的漏guaB突变体的分析。

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摘要

A leaky guaB mutant of Salmonella typhimurium LT-2 was obtained during a selection for mutants resistant to a combination of the two pyrimidine analogs, 5-fluorouracil and 5-fluorouridine. In the absence of exogenous guanine compounds, the growth rate of this mutant is limited by the endogenous supply of guanine nucleotides due to a defective inosine 5'-monophosphate dehydrogenase. Under these conditions the guanosine 5'-triphosphate pool is about 20% of normal, the cytidine 5'-triphosphate pool is reduced to below 60%, and the uridine 5'-triphosphate pool is slightly elevated. Simultaneously, levels of the pyrimidine biosynthetic enzymes are abnormal: aspartate transcarbamylase, orotate phosphoribosyltransferase, and orotidylic acid decarboxylase levels are increased 4-, 11-, and 3-fold, respectively. Levels of dihydroorotase and dihydroorotate dehydrogenase are decreased to 10 and 20%, respectively. The pyrimidine metabolism of the guaB mutant is restored completely by addition of guanine (or xanthine) to the growth medium. The data indicate purine nucleotide involvement in the regulation of expression of the pyr genes of S. typhimurium.
机译：在选择对两种嘧啶类似物5-氟尿嘧啶和5-氟尿苷的组合具有抗性的突变体的过程中，获得了鼠伤寒沙门氏菌LT-2的漏泄guaB突变体。在不存在外源鸟嘌呤化合物的情况下，由于肌苷5'-单磷酸脱氢酶缺陷，该突变体的生长速率受到鸟嘌呤核苷酸内源供应的限制。在这些条件下，鸟苷5'-三磷酸池约为正常值的20％，胞苷5'-三磷酸池降至60％以下，尿苷5'-三磷酸池略有升高。同时，嘧啶生物合成酶的水平异常：天冬氨酸转氨甲酰酶，乳清酸磷酸核糖基转移酶和牛膝二酸脱羧酶水平分别增加了4倍，11倍和3倍。二氢乳清酸酶和二氢乳清酸脱氢酶的水平分别降低至10％和20％。 guaB突变体的嘧啶代谢可通过在生长培养基中添加鸟嘌呤（或黄嘌呤）来完全恢复。数据表明嘌呤核苷酸参与鼠伤寒沙门氏菌pyr基因表达的调控。

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