Petit C, Rigg G P, Pazzani C, Smith A, Sieberth V, Stevens M, Boulnois G, Jann K, Roberts I S
Department of Microbiology and Immunology, University of Leicester, UK.
Mol Microbiol. 1995 Aug;17(4):611-20. doi: 10.1111/j.1365-2958.1995.mmi_17040611.x.
The nucleotide sequence of region 2 of the Escherichia coli K5 capsule gene cluster has been determined. This region, essential for the biosynthesis of the K5 polysaccharide, contained four genes, termed kfiA-D. The G + C ratio was 33.4%, which was lower than the typical G + C ratio for E. coli and that of the flanking regions 1 and 3 in the K5 capsule gene cluster. Three major RNA transcripts were detected within region 2 by Northern blotting and three promoters located by transcript mapping. Promoter activity was confirmed by promoter-probe analysis. The predicted amino acid sequence of KfiC had homology to a number of glycosyl transferase enzymes and overexpression of the KfiC gene resulted in increased K5 transferase activity. The predicted amino acid sequence of KfiD had homology to a number of NAD-dependent dehydrogenase enzymes and was demonstrated to be a UDP-glucose dehydrogenase that catalyses the information of UDP-glucuronic acid from UDP-glucose.
已确定大肠杆菌K5荚膜基因簇区域2的核苷酸序列。该区域对K5多糖的生物合成至关重要，包含四个基因，称为kfiA - D。其G + C含量为33.4%，低于大肠杆菌的典型G + C含量以及K5荚膜基因簇侧翼区域1和3的G + C含量。通过Northern印迹法在区域2内检测到三种主要RNA转录本，并通过转录图谱定位了三个启动子。通过启动子探针分析证实了启动子活性。KfiC的预测氨基酸序列与多种糖基转移酶具有同源性，KfiC基因的过表达导致K5转移酶活性增加。KfiD的预测氨基酸序列与多种NAD依赖性脱氢酶具有同源性，并被证明是一种UDP - 葡萄糖脱氢酶，可催化从UDP - 葡萄糖生成UDP - 葡糖醛酸。
