Kenyon Johanna J, Cunneen Monica M, Reeves Peter R
School of Molecular Bioscience, The University of Sydney, Sydney, NSW 2006, Australia.
Institute of Health and Biomedical Innovation, Queensland University of Technology. Brisbane, QLD 4001, Australia.
FEMS Microbiol Rev. 2017 Mar 1;41(2):200-217. doi: 10.1093/femsre/fux002.
O-antigen polysaccharide is a major immunogenic feature of the lipopolysaccharide of Gram-negative bacteria, and most species produce a large variety of forms that differ substantially from one another. There are 18 known O-antigen forms in the Yersinia pseudotuberculosis complex, which are typical in being composed of multiple copies of a short oligosaccharide called an O unit. The O-antigen gene clusters are located between the hemH and gsk genes, and are atypical as 15 of them are closely related, each having one of five downstream gene modules for alternative main-chain synthesis, and one of seven upstream modules for alternative side-branch sugar synthesis. As a result, many of the genes are in more than one gene cluster. The gene order in each module is such that, in general, the earlier a gene product functions in O-unit synthesis, the closer the gene is to the 5΄ end for side-branch modules or the 3΄ end for main-chain modules. We propose a model whereby natural selection could generate the observed pattern in gene order, a pattern that has also been observed in other species.
O抗原多糖是革兰氏阴性菌脂多糖的主要免疫原性特征，大多数菌种会产生大量彼此差异显著的形式。在假结核耶尔森氏菌复合体中有18种已知的O抗原形式，其典型特征是由一种名为O单元的短寡糖的多个拷贝组成。O抗原基因簇位于hemH和gsk基因之间，它们是非典型的，因为其中15个紧密相关，每个都有五个下游基因模块之一用于替代主链合成，以及七个上游模块之一用于替代侧链糖合成。因此，许多基因存在于不止一个基因簇中。每个模块中的基因顺序是这样的，一般来说，一个基因产物在O单元合成中发挥作用越早，该基因在侧链模块中就越靠近5΄端，在主链模块中就越靠近3΄端。我们提出了一个模型，通过该模型自然选择可以产生观察到的基因顺序模式，这种模式在其他物种中也有观察到。
