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首页> 外文期刊>Journal of Molecular Biology >carP, Involved in Py.rimidine Regulation of the Escherichia coli Carbamoylphosphate Synthetase Operon Encodes a Sequence-specific DMA-binding Protein Identical to XerB and PepA, also Required for Resolution of ColEI Multimers
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carP, Involved in Py.rimidine Regulation of the Escherichia coli Carbamoylphosphate Synthetase Operon Encodes a Sequence-specific DMA-binding Protein Identical to XerB and PepA, also Required for Resolution of ColEI Multimers

机译：carP，参与大肠杆菌氨甲酰磷酸合成酶Operon的嘧啶嘧啶调节，编码与XerB和PepA相同的序列特异性DMA结合蛋白，也是解决ColEI多聚体所必需的

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摘要

The carP gene involved in pyrimidine-specific regulation of the upstream PI promoter of the Escherichia coli carAB operon has been cloned in vivo on a mini-Mu replicon, sequenced and shown to be identical to the xerB (pepA) gene encoding aminopeptidase A, a protein also involved in the Xer-mediated site-specific recombination at ColEI cer. The trans-dominant allele carP6 was cloned as well and shown to bear a single G->A transition that converts the TGG codon (Trp473) into a TAG amber stop codon. Thetruncated mutant protein, missing the 31 C-terminal amino acid residues, was shown to be partially active; in the multicopy state the carP6 allele can restore pyrimidine repressibility of the carAB promoter PI. The trans-dominant character of the singlecopy carP6 allele was found to be suppressed in the presence of multiple copies of the wild-type gene. The carP (pepA) control region was sequenced and transcription shown to be initiated at three promoters, the most upstream one of which was shown to be subject to negative autoregulation. The aminopeptidase activity of CarP (PepA) was found to be dispensable for its role in pyrimidine-mediated repression of carAB transcription. CarP (PepA) was shown to be a sequence-specific DNA-binding protein that does not require, at least not in vitro, any pyrimidine cofactor to bind to the DNA. Mobility-shift and DNase I footprinting experiments have revealed a specific binding of purified CarP (PepA) to two sites in each one of the control regions of the E. coli and Salmonella typhimurium carAB operons and to a single site in the carP (pepA) ' control region. We propose that integration host factor and CarP/PepA-induced structural modifications in the carAB control region cause confor-mational changes requiredto assemble a pyrimidine-specific nucleo-protein regulatory complex.
机译：已在mini-Mu复制子上体内克隆了涉及大肠杆菌carAB操纵子上游PI启动子的嘧啶特异性调节的carP基因，测序并显示出与编码氨肽酶A的xerB（pepA）基因相同。该蛋白还参与了ColEI cer中Xer介导的位点特异性重组。还克隆了反主导的等位基因carP6，并显示出具有单个G-> A过渡，该过渡将TGG密码子（Trp473）转换为TAG琥珀色终止密码子。缺失31个C端氨基酸残基的截短的突变蛋白显示出部分活性。在多拷贝状态下，carP6等位基因可以恢复carAB启动子PI的嘧啶阻遏性。发现在存在多个拷贝的野生型基因的情况下，单拷贝carP6等位基因的反显性特征被抑制。对carP（pepA）控制区进行了测序，显示转录在三个启动子处启动，其中最上游的一个显示受到负自动调节。发现CarP（PepA）的氨肽酶活性在嘧啶介导的carAB转录抑制中起着不可或缺的作用。 CarP（PepA）被证明是一种序列特异性的DNA结合蛋白，它至少在体外不需要任何嘧啶辅助因子与DNA结合。迁移和DNase I足迹实验表明，纯化的CarP（PepA）与大肠杆菌和鼠伤寒沙门氏菌carAB操纵子的每个对照区域的两个位点以及carP（pepA）的单个位点具有特异性结合控制区域。我们建议，整合宿主因子和carAB控制区域中CarP / PepA诱导的结构修饰引起装配嘧啶特异性核蛋白调节复合物所需的构象变化。

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