Gemmill R M, Wessler S R, Keller E B, Calvo J M
Proc Natl Acad Sci U S A. 1979 Oct;76(10):4941-5. doi: 10.1073/pnas.76.10.4941.
The nucleotide sequence of the control region of the leu operon of Salmonella typhimurium was determined. A prominent feature of this region is a signal for termination of transcription. In vitro, transcription does terminate at this site, yielding a leader RNA of about 160 nucleotides as a major product. This leader RNA is potentially translatable into a peptide containing 28 amino acids, 4 of which are adjacent leucine residues. Several regions of base complementarity exist within the leader, positioned such that pairing of one region precludes pairing of another. The position of the four leucine codons relative to two regions of base complementarity suggest a model for the regulation of the leu operon similar to that proposed by Yanofsky and coworkers for the trp operon. In addition, a third region of base complementarity was identified which, when incorporated into the model, explains why premature termination is the usual outcome when transcription is initiated in vitro by purified RNA polymerase.
测定了鼠伤寒沙门氏菌亮氨酸操纵子调控区的核苷酸序列。该区域的一个显著特征是转录终止信号。在体外，转录确实在此位点终止，产生约160个核苷酸的前导RNA作为主要产物。这种前导RNA有可能被翻译成一个含有28个氨基酸的肽，其中4个是相邻的亮氨酸残基。在前导区内存在几个碱基互补区域，其位置使得一个区域的配对排除了另一个区域的配对。四个亮氨酸密码子相对于两个碱基互补区域的位置提示了一种类似于Yanofsky及其同事为色氨酸操纵子提出的亮氨酸操纵子调控模型。此外，还鉴定出了第三个碱基互补区域，当将其纳入该模型时，可以解释为什么在体外由纯化的RNA聚合酶启动转录时，过早终止是常见的结果。
