Suppression of IIIGlc‐defects by Enzymes IINag and IIBgl of the PEP:carbohydrate phosphotransferase system
Suppression of IIIGlc‐defects by Enzymes IINag and IIBgl of the PEP:carbohydrate phosphotransferase system
复制标题
PEP：碳水化合物磷酸转移酶系统的酶 IINag 和 IIBgl 对 IIIGlc 缺陷的抑制
作者：
A. Vogler;C. Broekhuizen;A. Schuitema;J. Lengeler;P. Postma
PEP的酶II：对N-乙酰葡糖胺（IINag）和β-葡糖苷（IIBgl）具有特异性的碳水化合物磷酸转移酶系统（PTS），含有与PTS的酶IIIGlc具有同源性的C末端结构域。我们研究了酶II中的一种或两种是否可以在功能上替代IIIGlc。获得了以下结果：（i）由染色体或质粒编码的nagE+基因合成的酶IINag可以通过相应的酶II在葡萄糖、甲基α-葡萄糖苷和蔗糖转运中取代IIIGlc。在N端结构域中具有大的缺失但具有完整C端结构域的酶IINag也可以在IIGlc依赖性葡萄糖转运中替代IIIGlc。（ii）在大肠杆菌bgl操纵子解密后，酶IIBgl可以替代IIIGlc。(iii)通过IINag/IIGlc的甲基α-葡萄糖苷的磷酸-HPr-依赖性磷酸化被抗IIIGlc的抗血清抑制，通过IINag的N-乙酰葡糖胺磷酸化也是如此。(iv)在含有编码IINag的质粒的菌株中，用抗IIIGlc的抗血清可以检测到分子量为62000 D的蛋白条带。我们从这些结果得出结论，酶IINag和IIBgl的IIIGlc样结构域可以在IIIGlc依赖性碳水化合物转运和磷酸化中取代IIIGlc。
The Enzymes II of the PEP:carbohydrate phosphotransferase system (PTS) specific for N‐acetylglucosamine (IINag) and β‐glucosides (IIBgl) contain C‐terminal domains that show homology with Enzyme IIIGlc of the PTS. We investigated whether one or both of the Enzymes II could substitute functionally for IIIGlc. The following results were obtained: (i) Enzyme IINag, synthesized from either a chromosomal or a plasmidencoded nagE+ gene could replace IIIGlc in glucose, methyl α‐glucoside and sucrose transport via the corresponding Enzymes II. An Enzyme IINag with a large deletion in the N‐terminal domain but with an intact C‐terminal domain could also replace IIIGlc in IIGlc‐dependent glucose transport, (ii) After decryptification of the Escherichia coli bgl operon, Enzyme IIBgl could substitute for IIIGlc. (iii) Phospho‐HPr‐dependent phosphorylation of methyl α‐glucoside via IINag/IIGlc is inhibited by antiserum against IIIGlc as is N‐acetyl‐glucosamine phosphorylation via IINag. (iv) In strains that contained the plasmid which coded for IINag, a protein band with a molecular weight of 62000 D could be detected with antiserum against IIIGlc. We conclude from these results that the IIIGlc‐like domain of Enzyme IINag and IIBgl can replace IIIGlc in IIIGlc‐dependent carbohydrate transport and phosphorylation.