Gene products required for surface expression of the capsular form of the group 1 K antigen in Escherichia coli (09a:K30)
Gene products required for surface expression of the capsular form of the group 1 K antigen in Escherichia coli (09a:K30)
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DOI：
10.1046/j.1365-2958.1999.01277.x
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发表时间：
1999-03-01
影响因子：
3.6
通讯作者：
Whitfield, C
中科院分区：
文献类型：
--
作者：
Drummelsmith, J;Whitfield, C
来自大肠杆菌的K30组抗原(O9A：K30)存在于细胞表面，既是由高相对分子质量的K30多糖组成的囊状结构，也是以短K30寡糖的形式存在于脂多糖分子(K30(LPS))中，与脂A核心相连。为了确定导致这两种形式的K抗原的分子过程，已经确定了16kb的染色体cps区，该区域编码了K30抗原的合成、聚合和易位所需的12个基因产物。这些基因产物包括负责合成K30重复单位的四个糖基转移酶；一个PST(1)出口蛋白(Wzx)，它需要将脂质连接的K30单位通过质膜转移到周质空间；以及一个K30抗原聚合酶(Wzy)。这些基因产物是O-抗原生物合成基因簇中的典型产物，它们与脂多糖转位途径相互作用，在细胞表面表达K30(内毒素)。同样的基因产物也为胶囊组装途径提供生物合成中间体，尽管它们本身不足以合成K30胶囊。另外三个基因wza、wzb和wzc编码蛋白质的同源物，这些蛋白质是由参与各种细菌胞外多糖表达的基因簇编码的。突变分析表明，Wza和Wzc是外膜结构野生型表面表达所必需的，但不是聚合所必需的，在K30LPS的转位中也不起作用。这些表面表达成分提供了区分O抗原和包膜组装系统的关键特征。
The group 1 K30 antigen from Escherichia coli (O9a:K30) is present on the cell surface as both a capsular structure composed of high-molecular-weight K30 polysaccharide and as short K30 oligosaccharides linked to lipid A-core in a lipopolysaccharide molecule (K30(LPS)). To determine the molecular processes that are responsible for the two forms of K antigen, the 16 kb chromosomal cps region has been characterized, This region encodes 12 gene products required for the synthesis, polymerization and translocation of the K30 antigen. The gene products include four glycosyltransferases responsible for synthesis of the K30 repeat unit; a PST(1) exporter (Wzx), required to transfer lipid-linked K30 units across the plasma membrane to the periplasmic space; and a K30-antigen polymerase (Wzy). These gene products are typical of those seen in O-antigen biosynthesis gene clusters and they interact with the lipopolysaccharide translocation pathway to express K30(LPS) on the cell surface. The same gene products also provide the biosynthetic intermediates for the capsule assembly pathway, although they are not in themselves sufficient for synthesis of the K30 capsule. Three additional genes, wza, wzb and wzc, encode homologues to proteins that are encoded by gene clusters involved in expression of a variety of bacterial exopolysaccharides. Mutant analysis indicates that Wza and Wzc are required for wild-type surface expression of the capsular structure but are not essential for polymerization and play no role in the translocation of K30LPS These surface expression components provide the key feature that distinguishes the assembly systems for O antigens and capsules.