University of Central Florida, Orlando, 32826, USA.
Biochimie. 2010 Feb;92(2):171-7. doi: 10.1016/j.biochi.2009.11.006. Epub 2009 Nov 26.
Autotransporters are the most common virulence factors secreted from Gram-negative pathogens. Until recently, autotransporter folding and outer membrane translocation were thought to be self-mediated events that did not require accessory factors. Here, we report that two variants of the autotransporter plasmid-encoded toxin are secreted by a lab strain of Escherichia coli. Biophysical analysis and cell-based toxicity assays demonstrated that only one of the two variants was in a folded, active conformation. The misfolded variant was not produced by a pathogenic strain of enteroaggregative E. coli and did not result from protein overproduction in the lab strain of E. coli. Our data suggest a host-specific factor is required for efficient folding of plasmid-encoded toxin.
自动转运蛋白是革兰氏阴性病原体分泌的最常见的毒力因子。直到最近，自动转运蛋白的折叠和外膜易位还被认为是不需要辅助因子的自我介导事件。在这里，我们报告了两种变体的自动转运蛋白质粒编码毒素是由大肠杆菌的实验室菌株分泌的。生物物理分析和基于细胞的毒性测定表明，只有两种变体中的一种处于折叠的、活性构象。错误折叠的变体不是由聚集性肠致病性大肠杆菌的致病性菌株产生的，也不是由大肠杆菌的实验室菌株过度表达蛋白质引起的。我们的数据表明，宿主特异性因子是质粒编码毒素有效折叠所必需的。
