TMAO ANAEROBIC RESPIRATION IN ESCHERICHIA-COLI - INVOLVEMENT OF THE TOR OPERON
TMAO ANAEROBIC RESPIRATION IN ESCHERICHIA-COLI - INVOLVEMENT OF THE TOR OPERON
复制标题
DOI：
10.1111/j.1365-2958.1994.tb00393.x
复制
发表时间：
1994-03-01
影响因子：
3.6
通讯作者：
PASCAL, MC
中科院分区：
文献类型：
--
作者：
MEJEAN, V;IOBBINIVOL, C;PASCAL, MC
三甲胺N-氧化物（TMAO）呼吸系统受到底物的严格阳性控制。该性质被利用在miniMu复制子介导的TMAO正调控基因的启动子区的体内克隆中。该区域位于染色体上的22 min处，被证明控制由三个开放阅读框组成的转录单位的表达，分别命名为torC、torA和torD。五个假定的C型血红素结合位点内的TorC序列的存在下，以及特定的生化表征，表明torC编码43 - 300 Da的C型细胞色素。第二个开放阅读框torA被鉴定为TMAO还原酶的结构基因。预测的torA基因产物的氨基末端序列的纯化的TMAO还原酶的比较表明切割的39个氨基酸的信号肽，这是在协议的周质位置的酶。预测的TorA蛋白含有五个钼辅因子结合基序中发现的其他bisdoproteins和显示广泛的序列同源性与BisC和DmsA蛋白。正如预期的那样，torA中的插入导致TMAO还原酶的损失。第三个开放阅读框编码的22 500 Da多肽与数据库中列出的蛋白质没有任何相似性。
The trimethylamine N-oxide (TMAO) respiratory system is subject to a strict positive control by the substrate. This property was exploited in the performance of miniMu replicon-mediated in vivo cloning of the promoter region of gene(s) positively regulated by TMAO. This region, located at 22 min on the chromosome, was shown to control the expression of a transcription unit composed of three open reading frames, designated torC, torA and torD, respectively. The presence of five putative c-type haem-binding sites within the TorC sequence, as well as the specific biochemical characterization, indicated that torC encodes a 43 300 Da c-type cytochrome. The second open reading frame, torA, was identified as the structural gene for TMAO reductase. A comparison of the predicted amino-terminal sequence of the torA gene product to that of the purified TMAO reductase indicated cleavage of a 39 amino acid signal peptide, which is in agreement with the periplasmic location of the enzyme. The predicted TorA protein contains the five molybdenum cofactor-binding motifs found in other molybdoproteins and displays extensive sequence homology with BisC and DmsA proteins. As expected, insertions in torA led to the loss of TMAO reductase. The 22 500 Da polypeptide encoded by the third open reading frame does not share any similarity with proteins listed in data banks.