Ronson C W, Astwood P M, Downie J A
J Bacteriol. 1984 Dec;160(3):903-9. doi: 10.1128/jb.160.3.903-909.1984.
Cosmids containing C4-dicarboxylate transport (dct) genes were identified from a gene bank of Rhizobium leguminosarum DNA made in the broad-host-range vector pLAFR1 by their ability to complement R. trifolii dct mutants. The dct genes were further characterized by subcloning, restriction site mapping, and transposon Tn5 and Tn7 mutageneses. Three dct loci were identified within a 5.5-kilobase region of DNA, in the order dctA-dctB-dctC. The results suggested that dctA encoded a structural component necessary for C4-dicarboxylate transport, whereas dctB and dctC encoded positive regulatory elements, and that dctA was transcribed divergently from dctB and dctC. Expression of dctA and dctC was obtained from vector promoters in some pLAFR1- and pSUP106-based plasmids.
通过其对三叶草根瘤菌dct突变体的互补能力，从用广宿主范围载体pLAFR1构建的豌豆根瘤菌DNA基因文库中鉴定出含有C4-二羧酸转运（dct）基因的黏粒。通过亚克隆、限制酶切位点图谱分析以及转座子Tn5和Tn7诱变对dct基因进行了进一步表征。在一段5.5千碱基的DNA区域内鉴定出三个dct位点，顺序为dctA-dctB-dctC。结果表明，dctA编码C4-二羧酸转运所需的结构成分，而dctB和dctC编码正调控元件，并且dctA与dctB和dctC呈反向转录。在一些基于pLAFR1和pSUP106的质粒中，从载体启动子获得了dctA和dctC的表达。
