Heinrichs D E, Monteiro M A, Perry M B, Whitfield C
Department of Microbiology, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
J Biol Chem. 1998 Apr 10;273(15):8849-59. doi: 10.1074/jbc.273.15.8849.
In Escherichia coli F632, the 14-kilobase pair chromosomal region located between waaC (formerly rfaC) and waaA (kdtA) contains genes encoding enzymes required for the synthesis of the type R2 core oligosaccharide portion of lipopolysaccharide. Ten of the 13 open reading frames encode predicted products sharing greater than 90% total similarity with homologs in E. coli K-12. However, the products of waaK (rfaK) and waaL (rfaL) each resemble homologs in Salmonella enterica serovar Typhimurium but share little similarity with E. coli K-12. The F632 WaaK and WaaL proteins therefore define differences between the type R2 and K-12 outer core oligosaccharides of E. coli lipopolysaccharides. Based on the chemical structure of the core oligosaccharide of an E. coli F632 waaK::aacC1 mutant and in vitro glycosyltransferase analyses, waaK encodes UDP-N-acetylglucosamine:(glucose) lipopolysaccharide alpha1, 2-N-acetylglucosaminyltransferase. The WaaK enzyme adds a terminal GlcNAc side branch substituent that is crucial for the recognition of core oligosaccharide acceptor by the O-polysaccharide ligase, WaaL. Results of complementation analyses of E. coli K-12 and F632 waaL mutants suggest that structural differences between the WaaL proteins play a role in recognition of, and interaction with, terminal lipopolysaccharide core moieties.
在大肠杆菌F632中，位于waaC（原rfaC）和waaA（kdtA）之间的14千碱基对染色体区域包含编码合成脂多糖R2型核心寡糖部分所需酶的基因。13个开放阅读框中的10个编码的预测产物与大肠杆菌K-12中的同源物具有超过90%的总体相似性。然而，waaK（rfaK）和waaL（rfaL）的产物分别类似于鼠伤寒沙门氏菌血清型鼠伤寒沙门氏菌中的同源物，但与大肠杆菌K-12的相似性很小。因此，F632 WaaK和WaaL蛋白定义了大肠杆菌脂多糖R2型和K-12型外核心寡糖之间的差异。基于大肠杆菌F632 waaK::aacC1突变体核心寡糖的化学结构和体外糖基转移酶分析，waaK编码UDP-N-乙酰葡糖胺：（葡萄糖）脂多糖α1,2-N-乙酰葡糖胺基转移酶。WaaK酶添加了一个末端GlcNAc侧链取代基，这对于O-多糖连接酶WaaL识别核心寡糖受体至关重要。大肠杆菌K-12和F632 waaL突变体的互补分析结果表明，WaaL蛋白之间的结构差异在识别和与末端脂多糖核心部分相互作用中起作用。
