pyrH-encoded UMP-kinase directly participates in pyrimidine-specific modulation of promoter activity in Escherichia coli
pyrH-encoded UMP-kinase directly participates in pyrimidine-specific modulation of promoter activity in Escherichia coli
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DOI：
10.1006/jmbi.1998.1910
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发表时间：
1998-07-24
影响因子：
5.6
通讯作者：
Glansdorff, N
中科院分区：
文献类型：
--
作者：
Kholti, A;Charlier, D;Glansdorff, N
大肠杆菌K-12和鼠伤寒沙门氏菌LT2的carAB操纵子编码这些生物唯一的氨基甲酰磷酸合成酶（CPSase），由两个启动子依次转录，上游的carP1和下游的carP2，分别被嘧啶和精氨酸抑制。我们提供的证据表明，pyrH基因产物（六聚体ump激酶）直接参与嘧啶特异性控制carP1活性，事实上，我们已经在大肠杆菌中分离出一种特殊类型的pyrH突变（pyrH41），它保留了准正常的ump激酶活性，但pet在大肠杆菌和鼠伤寒沙门氏菌的carAB操纵子P1启动子的嘧啶特异性抑制中受损。此外，在这个pyrH突变体中，carP1启动子上游腺嘌呤-106的体内Dam甲基化酶修饰的嘧啶依赖抑制被改变。隐性pyrH41等位基因具有单个C-G到a - t的翻转，可将丙氨酸94转化为谷氨酸（A94E）。虽然pyrH41的过表达导致ump激酶水平远高于野生型菌株，但在这些条件下，carAB操纵子的嘧啶特异性抑制并未恢复。同样,UMP-CMP-kinase基因的超表达的盘基网柄菌discoideum pyrH41突变不恢复pyrimidine-mediated卡尔P1启动子控制活动,尽管高架UMP-kinase活动以这样的转化株。这些结果表明，除了在从头合成嘧啶生物合成中的催化功能外，大肠杆菌ump -激酶还在调节carAB操纵子中发挥了额外的作用，但以前未被认识到。ump -激酶可能作为内部嘧啶核苷酸库的真正传感器，并与整合宿主因子（IHF）和氨基肽酶A （PepA别名CarP和XerB）协同作用，形成嘧啶特异性抑制carP1启动子活性所需的复杂核蛋白结构。(C) 1998学术出版社。
The carAB operon of the enterics Escherichia coli K-12 and Salmonella typhimuruim LT2, encoding the sole carbamoylphosphate synthetase (CPSase) of these organisms, is transcribed from two promoters in tandem, carP1 upstream and carP2 downstream, repressed respectively by pyrimidines and arginine. We present evidence that the pyrH gene product (the hexameric UMP-kinase) directly participates in the pyrimidine-specific control of carP1 activity, indeed, we have isolated in E. coli a particular type of pyrH mutation (pyrH41) that retains a quasi-normal UMP-kinase activity, but pet is impaired in the pyrimidine-specific repression of the P1 promoter of the carAB operon of E. coli and of S. typhimurium. Moreover, the pyrimidine-dependent inhibition of in vivo Dam methylase modification of adenine -106 upstream of the carP1 promoter is altered in this pyrH mutant. The recessive pyrH41 allele bears a single C-G to A-T transversion that converts alanine 94 into glutamic acid (A94E). Although overexpression of pyrH41 results in UMP-kinase levels far above that of a wild-type strain, pyrimidine-specific repression of the carAB operon is not restored under these conditions. Similarly, overexpression of the UMP-CMP-kinase gene of Dictyostelium discoideum in the pyrH41 mutant does not restore pyrimidine-mediated control of cal P1 promoter activity, in spite of the elevated UMP-kinase activity measured in such transformants. These results indicate that besides its catalytic function in the de novo pyrimidine biosynthesis, E. coli UMP-kinase fulfils an additional, but previously unrecognized role in the regulation of the carAB operon. UMP-kinase might function as the real sensor of the internal pyrimidine nucleotide pool and act in concert with the integration host factor (IHF) and aminopeptidase A (PepA alias CarP and XerB) in the elaboration of the complex nucleoprotein structure required for pyrimidine-specific repression of carP1 promoter activity. (C) 1998 Academic Press.