Identification of an O-Acyltransferase Gene (oacB) That Mediates 3-and 4-O-Acetylation of Rhamnose III in Shigella flexneri O Antigens
Identification of an O-Acyltransferase Gene (oacB) That Mediates 3-and 4-O-Acetylation of Rhamnose III in Shigella flexneri O Antigens
复制标题
介导福氏志贺菌 O 抗原中鼠李糖 III 3-和 4-O-乙酰化的 O-酰基转移酶基因 (oacB) 的鉴定
DOI：
10.1128/jb.01393-13
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发表时间：
2014-04-01
影响因子：
3.2
通讯作者：
Sun, Qiangzheng
中科院分区：
文献类型：
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作者：
Wang, Jianping;Knirel, Yuriy A.;Sun, Qiangzheng
O抗原（O多糖）是存在于细胞表面的重要且高度可变的细胞组分，其定义了革兰氏阴性菌的血清特异性。福氏志贺菌（志贺菌病的一个病因）的大多数O抗原共享由-> 2）-α-L-Rhap（III）-（1 -> 2）-α-L-Rhap（II）-（1 -> 3）-α-L-Rhap（I）-（1 -> 3）-β-D-GlcpNAc-（1 ->）重复组成的骨架，其可通过添加各种取代基来修饰，产生19种血清型。已知的修饰包括各种糖残基上的葡糖基化、Rha（I）上的O-乙酰化以及Rha（II）或/和Rha（III）上的磷酸乙醇胺磷酸化。最近，两个新的O-抗原修饰，即在位置3或4的Rha（III）和位置6的GlcNAc的O-乙酰化，已被确定在几个S。弗氏血清型。在这项工作中，3/4-O-乙酰化的Rha（III）的遗传基础被阐明。对S.弗氏血清型2a菌株Sf 301在Rha（III）上携带3/4-O-乙酰化，揭示了命名为oacB的O-酰基转移酶基因。遗传研究与O-抗原结构分析相结合表明，该基因负责血清型1a、1b、2a、5a和Y中的3/4-O-乙酰化，但不负责血清型6中的3/4-O-乙酰化，后者具有不同的O-抗原骨架结构。oacB基因由位于染色体proA-adrA区域的转座子样结构携带，这代表了S.弗莱克斯内里。这些发现加深了我们对S. flexneri O-抗原修饰，揭示了新的O-抗原变体的起源。
O antigen (O polysaccharide) is an important and highly variable cell component present on the surface of cells which defines the serospecificity of Gram-negative bacteria. Most O antigens of Shigella flexneri, a cause of shigellosis, share a backbone composed of -> 2)-alpha-L-Rhap(III)-(1 -> 2)-alpha-L-Rhap(II)-(1 -> 3)-alpha-L-Rhap(I)-(1 -> 3)-beta-D-GlcpNAc-(1 -> repeats, which can be modified by adding various substituents, giving rise to 19 serotypes. The known modifications include glucosylation on various sugar residues, O-acetylation on Rha(I), and phosphorylation with phosphoethanolamine on Rha(II) or/and Rha(III). Recently, two new O-antigen modifications, namely, O-acetylation at position 3 or 4 of Rha(III) and position 6 of GlcNAc, have been identified in several S. flexneri serotypes. In this work, the genetic basis for the 3/4-O-acetylation on Rha(III) was elucidated. Bioinformatic analysis of the genome of S. flexneri serotype 2a strain Sf301, which carries 3/4-O-acetylation on Rha(III), revealed an O-acyltransferase gene designated oacB. Genetic studies combined with O-antigen structure analysis demonstrated that this gene is responsible for the 3/4-O-acetylation in serotypes 1a, 1b, 2a, 5a, and Y but not serotype 6, which has a different O-antigen backbone structure. The oacB gene is carried by a transposon-like structure located in the proA-adrA region on the chromosome, which represents a novel mechanism of mobilization of O-antigen modification factors in S. flexneri. These findings enhance our knowledge of S. flexneri O-antigen modifications and shed light on the origin of new O-antigen variants.