Elliott S J, Hutcheson S W, Dubois M S, Mellies J L, Wainwright L A, Batchelor M, Frankel G, Knutton S, Kaper J B
Center for Vaccine Development and Department of Microbiology and Immunology, University of Maryland School of Medicine, 685 W Baltimore St, Baltimore, MD 21201, USA.
Mol Microbiol. 1999 Sep;33(6):1176-89. doi: 10.1046/j.1365-2958.1999.01559.x.
The locus of enterocyte effacement of enteropathogenic Escherichia coli encodes a type III secretion system, an outer membrane protein adhesin (intimin, the product of eae ) and Tir, a translocated protein that becomes a host cell receptor for intimin. Many type III secreted proteins require chaperones, which function to stabilize proteins, prevent inappropriate protein-protein interactions and aid in secretion. An open reading frame located between tir and eae, previously named orfU, was predicted to encode a protein with partial similarity to the Yersinia SycH chaperone. We examined the potential of the orfU gene product to serve as a chaperone for Tir. The orfU gene encoded a 15 kDa cytoplasmic protein that specifically interacted with Tir as demonstrated by the yeast two-hybrid assay, column binding and coimmunoprecipitation experiments. An orfU mutant was defective in attaching-effacing lesion formation and Tir secretion, but was unaffected in expression of other virulence factors. OrfU appeared to stabilize Tir levels in the cytoplasm, but was not absolutely necessary for secretion of Tir. Based upon the physical similarities, phenotypic characteristics and the demonstrated interaction with Tir, orfU is redesignated as cesT for the chaperone for E. coli secretion of T ir.
肠致病性大肠杆菌的肠细胞脱落位点编码一种III型分泌系统、一种外膜蛋白黏附素（紧密素，eae的产物）以及Tir，一种转位蛋白，它会成为紧密素的宿主细胞受体。许多III型分泌蛋白需要分子伴侣，这些分子伴侣的功能是稳定蛋白质、防止不适当的蛋白质-蛋白质相互作用并协助分泌。位于tir和eae之间的一个开放阅读框，之前被命名为orfU，预计编码一种与耶尔森菌SycH分子伴侣有部分相似性的蛋白质。我们研究了orfU基因产物作为Tir分子伴侣的潜力。orfU基因编码一种15 kDa的胞质蛋白，通过酵母双杂交试验、柱结合和免疫共沉淀实验证明，该蛋白与Tir特异性相互作用。一个orfU突变体在附着-脱落损伤形成和Tir分泌方面存在缺陷，但在其他毒力因子的表达上没有受到影响。OrfU似乎能稳定细胞质中Tir的水平，但对于Tir的分泌不是绝对必需的。基于物理相似性、表型特征以及与Tir已证明的相互作用，orfU被重新命名为cesT，即大肠杆菌分泌Tir的分子伴侣。
