Post L E, Arfsten A E, Davis G R, Nomura M
J Biol Chem. 1980 May 25;255(10):4653-59.
Previous studies showed that the gene for RNA polymerase subunit alpha at 72 min on the Escherichia coli chromosome is co-transcribed with genes for ribosomal proteins (r-proteins) S11, S4, and L17, and probably S13. DNA sequence analysis of a deletion mutant has now established that the S13 gene is a part of the alpha operon and the gene order is promoter (P alpha), rpsM (S13), rpsK (S11), rpsD(S4), rpoA(alpha), and rplQ(L17). The DNA sequence extending 650 bases before S13 gene was determined. In vitro transcription experiments establish the probable location of the alpha promoter (P alpha) within this sequence. The start site is 94 nucleotides upstream from the initiation codon (GUG) of the S13 gene. This promoter has features previously noted as common to E. coli promoters. However, comparison with four other sequenced promoters of r-protein operons shows no unique common features that might account for the common regulation of synthesis of r-proteins. This lack of sequence similarity in promoters of r-protein operons may be because r-protein synthesis is regulated at least partially at a post-transcriptional level.
先前的研究表明，大肠杆菌染色体上72分钟处的RNA聚合酶α亚基基因与核糖体蛋白（r蛋白）S11、S4和L17以及可能的S13基因共转录。现在，对一个缺失突变体的DNA序列分析已确定S13基因是α操纵子的一部分，基因顺序为启动子（Pα）、rpsM（S13）、rpsK（S11）、rpsD（S4）、rpoA（α）和rplQ（L17）。测定了S13基因之前延伸650个碱基的DNA序列。体外转录实验确定了α启动子（Pα）在该序列中的可能位置。起始位点在S13基因起始密码子（GUG）上游94个核苷酸处。该启动子具有先前指出的大肠杆菌启动子的共同特征。然而，与r蛋白操纵子的其他四个已测序启动子进行比较，未发现可能解释r蛋白合成共同调控的独特共同特征。r蛋白操纵子启动子缺乏序列相似性可能是因为r蛋白合成至少部分在转录后水平受到调控。
