Sequence diversity and antigenic variation at the rag locus of Porphyromonas gingivalis
Sequence diversity and antigenic variation at the rag locus of Porphyromonas gingivalis
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DOI：
10.1128/iai.73.7.4253-4262.2005
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发表时间：
2005-07-01
影响因子：
3.1
通讯作者：
Curtis, MA
中科院分区：
文献类型：
--
作者：
Hall, LMC;Fawell, SC;Curtis, MA
牙龈卟啉单胞菌 W50 的 rag 基因座编码 RagA（一种预测的 tonB 依赖性受体蛋白）和 RagB（一种构成免疫显性外膜抗原的脂蛋白）。该位点的低 G+C 含量、与移动元件的关联以及在物种中明显的受限分布表明该位点是通过水平基因转移产生的。在本研究中，我们证明了 rag 基因座有四个不同的等位基因。 W50 中发现的原始 rag 等位基因被重命名为 rag-1，而在缺乏 rag-L 的分离株中发现了 rag-2 至 rag-4 三个新等位基因。这三个新等位基因编码与 RagA1 具有 63% 至 71% 氨基酸同一性的 RagA 变体，并且彼此编码与 RagB 具有 43% 至 56% 氨基酸同一性的变体。 RagA/B 蛋白与许多拟杆菌蛋白具有同源性，包括与多糖摄取有关的 SusC/D。针对牙龈卟啉单胞菌 W50 的 RagB1 产生的单克隆和多克隆抗体不与来自携带不同等位基因的分离株的蛋白质发生交叉反应。在实验室收集的 168 个分离株中，26% 携带 rag-1，36% 携带 rag-2，25% 携带 rag-3，14% 携带 rag-4（包括模式菌株 ATCC 33277）。不同分离株中基因座的限制性谱证明了每个等位基因内的多态性，其中一些是由插入序列元件的存在或不存在引起的。参考之前发表的关于小鼠模型毒力的研究（M. L. Laine 和 A. J. van Winkelhoff, Oral Microbiol.Immunol. 13:322-325, 1998），在小鼠中引起严重疾病的分离株比其他 rag 等位基因更有可能携带 rag-1。
The rag locus of Porphyromonas gingivalis W50 encodes RagA, a predicted tonB-dependent receptor protein, and RagB, a lipoprotein that constitutes an immunodominant outer membrane antigen. The low G+C content of the locus, an association with mobility elements, and an apparent restricted distribution in the species suggested that the locus had arisen by horizontal gene transfer. In the present study, we have demonstrated that there are four divergent alleles of the rag locus. The original rag allele found in W50 was renamed rag-1, while three novel alleles, rag-2 to rag-4, were found in isolates lacking rag-L The three novel alleles encoded variants of RagA with 63 to 71% amino acid identity to RagA1 and each other and variants of RagB with 43 to 56% amino acid identity. The RagA/B proteins have homology to numerous Bacteroides proteins, including SusC/D, implicated in polysaccharide uptake. Monoclonal and polyclonal antibodies raised against RagB1 of P. gingivalis W50 did not cross-react with proteins from isolates carrying different alleles. In a laboratory collection of 168 isolates, 26% carried rag-1, 36% carried rag-2, 25% carried rag-3, and 14% carried rag-4 (including the type strain, ATCC 33277). Restriction profiles of the locus in different isolates demonstrated polymorphism within each allele, some of which is accounted for by the presence or absence of insertion sequence elements. By reference to a previously published study on virulence in a mouse model (M. L. Laine and A. J. van Winkelhoff, Oral Microbiol. Immunol. 13:322-325, 1998), isolates that caused serious disease in mice were significantly more likely to carry rag-1 than other rag alleles.