Jarvis K G, Girón J A, Jerse A E, McDaniel T K, Donnenberg M S, Kaper J B
Department of Medicine, Department of Veterans Affairs Medical Center, Baltimore, MD, USA.
Proc Natl Acad Sci U S A. 1995 Aug 15;92(17):7996-8000. doi: 10.1073/pnas.92.17.7996.
Enteropathogenic Escherichia coli (EPEC) causes a characteristic histopathology in intestinal epithelial cells called the attaching and effacing lesion. Although the histopathological lesion is well described the bacterial factors responsible for it are poorly characterized. We have identified four EPEC chromosomal genes whose predicted protein sequences are similar to components of a recently described secretory pathway (type III) responsible for exporting proteins lacking a typical signal sequence. We have designated the genes sepA, sepB, sepC, and sepD (sep, for secretion of E. coli proteins). The predicted Sep polypeptides are similar to the Lcr (low calcium response) and Ysc (yersinia secretion) proteins of Yersinia species and the Mxi (membrane expression of invasion plasmid antigens) and Spa (surface presentation of antigens) regions of Shigella flexneri. Culture supernatants of EPEC strain E2348/69 contain several polypeptides ranging in size from 110 kDa to 19 kDa. Proteins of comparable size were recognized by human convalescent serum from a volunteer experimentally infected with strain E2348/69. A sepB mutant of EPEC secreted only the 110-kDa polypeptide and was defective in the formation of attaching and effacing lesions and protein-tyrosine phosphorylation in tissue culture cells. These phenotypes were restored upon complementation with a plasmid carrying an intact sepB gene. These data suggest that the EPEC Sep proteins are components of a type III secretory apparatus necessary for the export of virulence determinants.
肠致病性大肠杆菌（EPEC）在肠道上皮细胞中会引发一种特征性的组织病理学变化，称为紧密黏附与消除性损伤。尽管这种组织病理学损伤已有详细描述，但其相关细菌因子的特征却知之甚少。我们已鉴定出四个EPEC染色体基因，其预测的蛋白质序列与最近描述的一种分泌途径（III型）的组分相似，该分泌途径负责输出缺乏典型信号序列的蛋白质。我们将这些基因命名为sepA、sepB、sepC和sepD（sep代表大肠杆菌蛋白质的分泌）。预测的Sep多肽与耶尔森菌属的Lcr（低钙应答）和Ysc（耶尔森菌分泌）蛋白以及福氏志贺菌的Mxi（侵袭质粒抗原的膜表达）和Spa（抗原的表面呈现）区域相似。EPEC菌株E2348/69的培养上清液含有几种大小在110 kDa至19 kDa之间的多肽。来自一名经实验感染E2348/69菌株的志愿者的恢复期血清识别出了大小相当的蛋白质。EPEC的sepB突变体仅分泌110-kDa的多肽，并且在组织培养细胞中形成紧密黏附与消除性损伤以及蛋白质酪氨酸磷酸化方面存在缺陷。当用携带完整sepB基因的质粒进行互补时，这些表型得以恢复。这些数据表明，EPEC的Sep蛋白是III型分泌装置的组分，该装置对于毒力决定因素的输出是必需的。
