Separate pathways for O acetylation of polymeric and monomeric sialic acidsand identification of sialyl O-acetyl esterase in Escherichia coli K1
Separate pathways for O acetylation of polymeric and monomeric sialic acidsand identification of sialyl O-acetyl esterase in Escherichia coli K1
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DOI：
10.1128/jb.00466-06
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发表时间：
2006-09-01
影响因子：
3.2
通讯作者：
Vimr, Eric R.
中科院分区：
文献类型：
--
作者：
Steenbergen, Susan M.;Lee, Young-Choon;Vimr, Eric R.
大肠杆菌K1的聚唾液酸胶囊中唾液酸残基的碳位置7或9处的O乙酰化由K1特异性原噬菌体CUS-3携带的相位可变应急位点neuO催化。在这里，我们描述了一种新的方法，用于分析聚合唾液酸O乙酰化，涉及释放表面唾液酸的内切-N-乙酰神经氨酸酶消化，然后通过荧光标记和检测喹喔啉酮衍生物的色谱法。结果表明，NeuO负责体内发生的大多数胶囊修饰。然而，检测到一个小的neuO-独立的O乙酰化途径，这是依赖于由neuD编码的双功能多肽。该途径涉及单体唾液酸的O乙酰化，并由另一种双功能酶NeuA调节，NeuA包括N-末端合成酶和C-末端唾液酸O-酯酶结构域。NeuA C-末端结构域（Pm 1710）在多杀性巴氏杆菌的同源物也被证明是一种酯酶，这表明它在乙酰化的环境唾液酸的催化剂的功能。我们的综合结果表明，在微生物唾液酸和聚唾液酸的合成和催化剂的一个以前意想不到的复杂性。这些发现是理解E. coli K1和其他物种，并可能为药物或疫苗开发提供新的靶点。
O acetylation at carbon positions 7 or 9 of the sialic acid residues in the polysialic acid capsule of Escherichia coli K1 is catalyzed by a phase-variable contingency locus, neuO, carried by the K1-specific prophage, CUS-3. Here we describe a novel method for analyzing polymeric sialic acid O acetylation that involves the release of surface sialic acids by endo-N-acetyineuraminidase digestion, followed by fluorescent labeling and detection of quinoxalinone derivatives by chromatography. The results indicated that NeuO is responsible for the majority of capsule modification that takes place in vivo. However, a minor neuO-independent O acetylation pathway was detected that is dependent on the bifunctional polypeptide encoded by neuD. This pathway involves O acetylation of monomeric sialic acid and is regulated by another bifunctional enzyme, NeuA, which includes N-terminal synthetase and C-terminal sialyl O-esterase domains. A homologue of the NeuA C-terminal domain (Pm1710) in Pasteurella multocida was also shown to be an esterase, suggesting that it functions in the catabolism of acetylated environmental sialic acids. Our combined results indicate a previously unexpected complexity in the synthesis and catabolism of microbial sialic and polysialic acids. These findings are key to understanding the biological functions of modified sialic acids in E. coli K1 and other species and may provide new targets for drug or vaccine development.