Determination of the transcription initiation site and identification of the protein product of the regulatory gene xylR for xyl operons on the TOL plasmid
Determination of the transcription initiation site and identification of the protein product of the regulatory gene xylR for xyl operons on the TOL plasmid
复制标题
TOL 质粒上 xyl 操纵子的调控基因 xylR 转录起始位点的确定和蛋白产物的鉴定
作者：
S. Inouye;A. Nakazawa;T. Nakazawa
xylR基因是TOL质粒上的调节基因，其以积极的方式作用于xyl操纵子，以降解恶臭假单胞菌中的甲苯和二甲苯。将含有xylR启动子区域的DNA片段克隆到启动子探测载体上，并测定其核苷酸序列。通过 S1 核酸酶和逆转录酶图谱确定恶臭假单胞菌和大肠杆菌细胞中 xylR 基因的转录起始位点。检测到两个起始位点，它们在恶臭假单胞菌和大肠杆菌中是相同的。两种细菌细胞中合成的 mRNA 量几乎相同，并且与木糖操纵子的诱导剂无关。大肠杆菌启动子的共有序列发现于各自转录起始位点之前的区域。 xylR基因的产物经maxicell系统鉴定为分子量约为67,000的蛋白质。
The xylR gene is a regulatory gene on the TOL plasmid, which acts in a positive manner on xyl operons for degradation of toluene and xylenes in Pseudomonas putida. A DNA fragment containing the xylR promoter region was cloned on promoter-probing vectors, and its nucleotide sequence was determined. The transcription initiation site of the xylR gene was determined in cells of P. putida and Escherichia coli by S1 nuclease and reverse transcriptase mapping. Two initiation sites were detected which were identical in both P. putida and E. coli. The amounts of mRNA synthesized in both bacterial cells were almost the same and independent of the inducers for xyl operons. The consensus sequences for E. coli promoters were found in the region preceding the respective transcription initiation sites. The product of the xylR gene was identified by the maxicell system as a protein with an approximate molecular weight of 67,000.