Ghim S Y, Kim C C, Bonner E R, D'Elia J N, Grabner G K, Switzer R L
Department of Biochemistry, University of Illinois, Urbana, Illinois 61801, USA.
J Bacteriol. 1999 Feb;181(4):1324-9. doi: 10.1128/JB.181.4.1324-1329.1999.
The 5' end of the Enterococcus faecalis pyr operon specifies, in order, the promoter, a 5' untranslated leader, the pyrR gene encoding the regulatory protein for the operon, a 39-nucleotide (nt) intercistronic region, the pyrP gene encoding a uracil permease, a 13-nt intercistronic region, and the pyrB gene encoding aspartate transcarbamylase. The 5' leader RNA is capable of forming stem-loop structures involved in attenuation control of the operon. No attenuation regions, such as those found in the Bacillus subtilis pyr operon, are present in the pyrR-pyrP or pyrP-pyrB intercistronic regions. Several lines of evidence demonstrate that the E. faecalis pyr operon is repressed by uracil via transcriptional attenuation at the single 5' leader termination site and that attenuation is mediated by the PyrR protein.
粪肠球菌pyr操纵子的5'端依次包含启动子、5'非翻译前导序列、编码该操纵子调节蛋白的pyrR基因、一个39个核苷酸（nt）的基因间区域、编码尿嘧啶通透酶的pyrP基因、一个13 nt的基因间区域以及编码天冬氨酸转氨甲酰酶的pyrB基因。5'前导RNA能够形成参与该操纵子衰减控制的茎环结构。在pyrR-pyrP或pyrP-pyrB基因间区域不存在诸如在枯草芽孢杆菌pyr操纵子中发现的那些衰减区域。多项证据表明，粪肠球菌pyr操纵子通过在单个5'前导序列终止位点的转录衰减被尿嘧啶抑制，并且衰减由PyrR蛋白介导。
