Titgemeyer F, Jahreis K, Ebner R, Lengeler J W
University of Groningen, Department of Biochemistry, The Netherlands.
Mol Gen Genet. 1996 Feb 5;250(2):197-206. doi: 10.1007/BF02174179.
The Klebsiella pneumoniae genes scrA and scrB are indispensable for sucrose (Scr) utilisation. Gene scrA codes for an Enzyme IIScr (IIScr) transport protein of the phosphoenolpyruvate-dependent carbohydrate: phosphotransferase system (PTS), while scrB encodes a sucrose 6-phosphate specific invertase. A 3.7 kbscr AB DNA fragment has been cloned from K. pneumoniae and expressed in Escherichia coli. Its nucleotide sequence was determined and the coding regions for scrA (1371 bp) and scrB (1401 bp) were identified by genetic complementation, enzyme activity test and radiolabelling of the gene products. In addition, the nucleotide sequence of the scrB gene from conjugative plasmid pUR400 isolated from Salmonella typhimurium was also determined and errors in the previously published sequence of the scrA gene of pUR400 were corrected. Extensive similarity was found between the sequences of ScrA and other Enzymes II, as well as between the two invertases and other sucrose hydrolysing enzymes. Based on the analysis of seven IIScr proteins, a hypothetical model of the secondary structure of IIScr is proposed.
肺炎克雷伯菌的基因scrA和scrB对于蔗糖（Scr）的利用是不可或缺的。基因scrA编码磷酸烯醇丙酮酸依赖性碳水化合物磷酸转移酶系统（PTS）的酶IIScr（IIScr）转运蛋白，而scrB编码蔗糖6-磷酸特异性转化酶。已从肺炎克雷伯菌中克隆出一个3.7 kb的scrAB DNA片段，并在大肠杆菌中表达。测定了其核苷酸序列，并通过遗传互补、酶活性测试和基因产物的放射性标记鉴定了scrA（1371 bp）和scrB（1401 bp）的编码区。此外，还测定了从鼠伤寒沙门氏菌分离的接合质粒pUR400中scrB基因的核苷酸序列，并纠正了先前发表的pUR400的scrA基因序列中的错误。在ScrA与其他酶II的序列之间，以及在这两种转化酶与其他蔗糖水解酶之间发现了广泛的相似性。基于对七种IIScr蛋白的分析，提出了IIScr二级结构的假设模型。
