Hediger M A, Johnson D F, Nierlich D P, Zabin I
Proc Natl Acad Sci U S A. 1985 Oct;82(19):6414-8. doi: 10.1073/pnas.82.19.6414.
The lac operon of Escherichia coli spans approximately 5300 base pairs and includes the lacZ, lacY, and lacA genes in addition to the operator, promoter, and transcription termination regions. We report here the sequence of the lacA gene and the region distal to it, confirming the sequence of thiogalactoside transacetylase and completing the sequence of the lac operon. The lacA gene is characterized by use of rare codons, suggesting an origin from a plasmid, transposon, or virus gene. UUG is the translation initiation codon. A preliminary examination of 3' end of the lac messenger in the region distal to the lacA gene indicates several endpoints. A predominant one is located at the 3' end of a G + C-rich hairpin structure, which may be involved in termination of transcription or in post-transcriptional processing. An open reading frame of 702 base pairs is present on the complementary strand downstream from lacA.
大肠杆菌的乳糖操纵子跨度约为5300个碱基对，除了操纵基因、启动子和转录终止区域外，还包括lacZ、lacY和lacA基因。我们在此报告lacA基因及其远端区域的序列，确认硫代半乳糖苷转乙酰酶的序列并完成乳糖操纵子的序列。lacA基因的特点是使用稀有密码子，这表明它起源于质粒、转座子或病毒基因。UUG是翻译起始密码子。对lacA基因远端区域的lac信使RNA 3'端的初步检查显示有几个终点。一个主要的终点位于富含G + C的发夹结构的3'端，这可能参与转录终止或转录后加工。在lacA下游的互补链上存在一个702个碱基对的开放阅读框。
