Loviny-Anderton T, Shaw P C, Shin M K, Hartley B S
Centre for Biotechnology, Imperial College of Science, Technology and Medicine, London, U.K.
Biochem J. 1991 Jul 1;277 ( Pt 1)(Pt 1):263-71. doi: 10.1042/bj2770263.
Arthrobacter strain N.R.R.L. B3728 superproduces a D-xylose isomerase that is also a useful industrial D-glucose isomerase. The gene (xylA) that encodes it has been cloned by complementing a xylA mutant of the ancestral strain, with the use of a shuttle vector. The 5' region shows strong sequence similarity to Escherichia coli consensus promoters and ribosome-binding sequences and allows high levels of expression in E. coli. The coding sequence shows similarity to those for other D-xylose isomerases and is followed by 22 nucleotide residues with stop codons in each reading frame, a good 'consensus' ribosome-binding site and an open reading frame showing similarity to those of known D-xylulokinases (xylB). Studies on the expression of the cloned gene in Arthrobacter and in E. coli suggest that the two genes are part of a xyl operon regulated by a repressor that is defective in strain B3728. Codon usage in these two genes, and in another open reading frame (nxi) that was adventitiously isolated during early cloning attempts, shows some characteristic omissions and a strong G + C preference in redundant positions.
节杆菌菌株N.R.R.L. B3728能超量产生一种D-木糖异构酶，该酶也是一种有用的工业用D-葡萄糖异构酶。编码该酶的基因（xylA）已通过使用穿梭载体对原始菌株的xylA突变体进行互补克隆得到。其5'区域与大肠杆菌共有启动子和核糖体结合序列具有很强的序列相似性，并能在大肠杆菌中实现高水平表达。编码序列与其他D-木糖异构酶的编码序列相似，后面跟着22个核苷酸残基，每个阅读框中都有终止密码子，一个良好的“共有”核糖体结合位点，以及一个与已知D-木酮糖激酶（xylB）的阅读框相似的开放阅读框。对克隆基因在节杆菌和大肠杆菌中的表达研究表明，这两个基因是由一种阻遏物调控的木糖操纵子的一部分，而在菌株B3728中该阻遏物存在缺陷。这两个基因以及在早期克隆尝试中偶然分离出的另一个开放阅读框（nxi）中的密码子使用情况，在冗余位置显示出一些特征性的遗漏和对G + C的强烈偏好。
