The SRS superfamily of Toxoplasma surface proteins
The SRS superfamily of Toxoplasma surface proteins
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DOI：
10.1016/j.ijpara.2003.12.004
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发表时间：
2004-03-09
影响因子：
4
通讯作者：
Grigg, ME
中科院分区：
文献类型：
--
作者：
Jung, C;Lee, CYF;Grigg, ME
弓形虫（Toxoplasma gondii）的表面包裹着一层发育表达的糖基磷脂酰肌醇连接蛋白，其结构与高免疫原性表面抗原SAG1相关。总的来说，这些表面抗原被称为SRS （sag1相关序列）超家族蛋白。SRS蛋白被认为介导与宿主细胞的附着并激活宿主免疫以调节寄生虫的毒力。为了更好地了解SRS基因的数量、进化和发育表达，本研究从生物信息学上鉴定了弓形虫II型Me49基因组中存在的161个独特的SRS DNA序列。SRS超家族序列在系统发育上分为两个亚家族，原型成员分别为SAG1和SAG2A。同源的SRS序列是24-99%相同的，串联排列在整个基因组中，并且存在于大多数（如果不是全部的话）染色体上。Ia和Ib染色体上的11个SRS序列均聚集在亚端粒表达位点。在大多数存在多个表达序列标签的SRS序列中，信使RNA的表达受发育调控。在具有内含子的SRS序列中，确定了围绕剪接受体和供体位点的一致核苷酸序列。SRS序列之间的基因型差异存在于几个位点上（例如SAG5B缺失，与RH相比，Me49中SAG2D被截断），表明不同的基因型具有不同的SRS序列集。同源基因仅限于组织居住的球虫（新孢子虫、肉囊虫），而在其他更远的顶复合体如艾美耳虫、隐孢子虫和疟原虫中没有相关序列。(C) 2004澳大利亚寄生虫学学会。Elsevier Ltd.出版。版权所有。
The surface of the protozoan parasite Toxoplasma gondii is coated with developmentally expressed, glycosylphosphatidylinositol-linked proteins structurally related to the highly immunogenic surface antigen SAG1. Collectively, these surface antigens are known as the SRS (SAG1-related sequences) superfamily of proteins. SRS proteins are thought to mediate attachment to host cells and activate host immunity to regulate the parasite's virulence. To better understand the number, evolution and developmental expression of SRS genes, this study has bioinformatically identified 161 unique SRS DNA sequences present in the T. gondii type II Me49 genome. The SRS superfamily of sequences phylogenetically bifurcates into two subfamilies, the prototypic, members being SAG1 and SAG2A, respectively. Paralogous SRS sequences are 24-99% identical, are tandemly arrayed throughout the genome, and are present on most, if not all, chromosomes. All 11 SRS sequences on chromosomes Ia and Ib are clustered at sub-telomeric expression sites. Messenger RNA expression in the majority of SRS sequences for which multiple Expressed Sequence Tags exist is developmentally regulated. A consensus nucleotide sequence surrounding both the splice acceptor and donor sites was identified in those SRS sequences possessing an intron. Genotypic differences among SRS sequences are present at several loci (e.g. the absence of SAG5B, the truncation of SAG2D in Me49 compared with RH) indicating that different genotypes possess distinct sets of SRS sequences. Orthologous genes are restricted to tissue-dwelling coccidia (Neospora, Sarcocystis) with no related sequences present in other more distant apicomplexa such as Eimeria, Cryptosporidia, and Plasmodium spp. (C) 2004 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.