Repression and induction of the nag regulon of Escherichia coll K‐12: the roles of nagC and nagA in maintenance of the uninduced state
Repression and induction of the nag regulon of Escherichia coll K‐12: the roles of nagC and nagA in maintenance of the uninduced state
复制标题
大肠杆菌 K-12 nag 调节子的抑制和诱导：nagC 和 nagA 在维持非诱导状态中的作用
DOI：
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发表时间：
1991
影响因子：
3.6
通讯作者：
J. Plumbridge
中科院分区：
文献类型：
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作者：
J. Plumbridge
位于大肠杆菌染色体上15.5 min处的nag调节子由两个不同的操纵子nagE和nagBACD组成，编码参与N-乙酰葡糖胺摄取和代谢的基因。通过插入抗生素抗性盒，在每个基因中产生了突变。携带nagE、B和A中插入的菌株的表型与先前鉴定的基因产物一致：nagE、EIINag（磷酸转移酶系统的N-乙酰葡糖胺特异性转运蛋白）和nagB和那牙（降解N-乙酰葡糖胺所必需的两种酶）。napC中的插入导致nag基因的去阻遏，这与nagC基因编码调节子的阻遏物的早期观察一致。那牙的插入也引起去阻遏，这意味着那牙在nag调节子的表达调节以及氨基糖的降解中起作用。N-乙酰葡糖胺-6-磷酸（N-乙酰葡糖胺转运的细胞内产物和那牙基因产物的底物）被证明是调节子的诱导剂，这表明那牙突变如何导致去阻遏：N-乙酰葡糖胺-6-磷酸脱乙酰酶的缺乏允许N-乙酰葡糖胺-6-磷酸积累并诱导调节子。
The nag regulon located at 15.5 min on the Escherichia coli chromosome consists of two divergent operons, nagE and nagBACD, encoding genes involved in the uptake and metabolism of N‐acetylglucosamine. Null mutations have been created in each of the genes by insertion of antibiotic resistance cartridges. The phenotypes of the strains carrying the insertions in nagE, B and A were consistent with the previous identification of gene products: nagE, EIINag, the N‐acetylglucosamine specific transporter of the phosphotransferase system and nagB and nagA, the two enzymes necessary for the degradation of N‐acetylglucosamine. Insertions in the napC result in derepression of the nag genes, which is consistent with earlier observations that the nagC gene encodes the repressor of the regulon. Insertions in nagA also provoke a derepression, implying that nagA has a role in the regulation of the expression of the nag regulon as well as in the degradation of the amino‐sugars. N‐acetylglucosamine‐6‐phosphate, the intra‐cellular product of N‐acetylglucosamine transport and the substrate of the nagA gene product, is shown to be an inducer of the regulon and this suggests how nagA mutations result in derepression: the absence of N‐acetylglucosamine‐6‐phosphate deacetylase allows N‐acetylglucosamine‐6‐phosphate to accumulate and induce the regulon.