Su Marcia Shu-Wei, Kao Hsi-Chun, Lin Ching-Nan, Syu Wan-Jr
Institute of Microbiology and Immunology, National Yang-Ming University, Beitou 112, Taipei, Taiwan.
Microbiology (Reading). 2008 Apr;154(Pt 4):1094-1103. doi: 10.1099/mic.0.2007/013946-0.
Escherichia coli O157:H7 tightly associates with host cells through the formation of a pedestal structure in which cell cytoskeleton rearrangement has been observed. These pathogenic properties have been attributed to an island, known as the locus of enterocyte effacement (LEE), located on the bacterial chromosome. Gene l0017 is one of the LEE genes that has been less well characterized. To understand further the function of the gene, an l0017-deleted mutant was created. The mutant lost type III protein secretion (TTS) capacity. In terms of intracellular components, there was a substantial decrease in the level of EspA, but no apparent effect on Tir and EspB was observed. Fractionation of the bacterial proteins indicated that L0017 was part of the inner-membrane fraction. This association with the membrane is consistent with the hypothesis that L0017 may act as one of the TTS components. In addition, L0017 was found to affect regulation of EspA at a post-transcriptional level. The presence of L0017 readily stabilized EspA and the interaction between L0017 and EspA was demonstrated by their co-purification as well as by a bacterial two-hybrid system. Therefore, L0017 is a chaperone, the second chaperone identified in this system after CesAB, and escorts EspA, a protein with a great tendency to polymerize.
大肠杆菌O157:H7通过形成一种基座结构与宿主细胞紧密结合，在这种结构中已观察到细胞骨架重排。这些致病特性归因于位于细菌染色体上的一个被称为肠上皮细胞脱落位点（LEE）的基因座。基因l0017是LEE基因中一个特征描述较少的基因。为了进一步了解该基因的功能，构建了一个l0017缺失突变体。该突变体丧失了III型蛋白分泌（TTS）能力。在细胞内成分方面，EspA水平大幅下降，但未观察到对Tir和EspB有明显影响。对细菌蛋白进行分级分离表明，L0017是内膜部分的一部分。这种与膜的关联与L0017可能作为TTS成分之一的假设一致。此外，发现L0017在转录后水平影响EspA的调控。L0017的存在使EspA易于稳定，并且通过它们的共纯化以及细菌双杂交系统证明了L0017与EspA之间的相互作用。因此，L0017是一种分子伴侣，是该系统中继CesAB之后鉴定出的第二种分子伴侣，它护送EspA，一种极易聚合的蛋白质。
