CfaD-dependent expression of a novel extracytoplasmic protein from enterotoxigenic Escherichia coli
CfaD-dependent expression of a novel extracytoplasmic protein from enterotoxigenic Escherichia coli
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DOI：
10.1128/jb.00131-07
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发表时间：
2007-07-01
影响因子：
3.2
通讯作者：
Munson, George P.
中科院分区：
文献类型：
--
作者：
Pilonieta, M. Carolina;Bodero, Maria D.;Munson, George P.
H10407是一种产肠毒素大肠杆菌(ETEC)，它利用CFA/I菌毛附着在小肠表面，在那里它阐述了导致人类大量水样腹泻的毒素。CFAD是AraC/XylS家族的一员，在转录水平上正向调节CFA/I菌毛的表达。DNase I足迹显示，该激活子在菌毛启动子cfaAp的上游有两个结合位点。一个从-23位延伸到-56位，另一个从-73位延伸到-103位(相对于cfaAp转录起始点的编号)。通过计算分析，预测了H10407基因组中还有其他CFAD结合位点。其中两个位点位于一个以前未确定特征的基因cexE的上游。体外DNase I足迹实验证实这两个位点都是真正的结合位点，cexEp：：LacZ报道证实cexE在体内的表达需要CFAD。CexE的氨基末端含有一个分泌信号肽，在跨细胞膜的转运过程中通过一般的分泌途径被移除。这些研究表明，CexE可能是ETEC的一个新的毒力因子，因为它的表达受毒力调节因子CFAD控制，其分布仅限于ETEC。
H10407 is a strain of enterotoxigenic Escherichia coli (ETEC) that utilizes CFA/I pili to adhere to surfaces of the small intestine, where it elaborates toxins that cause profuse watery diarrhea in humans. Expression of the CFA/I pilus is positively regulated at the level of transcription by CfaD, a member of the AraC/XylS family. DNase I footprinting revealed that the activator has two binding sites upstream of the pilus promoter cfaAp. One site extends from positions -23 to -56, and the other extends from positions -73 to -103 (numbering relative to the transcription start site of cfaAp). Additional CfaD binding sites were predicted within the genome of H10407 by computational analysis. Two of these sites lie upstream of a previously uncharacterized gene, cexE. In vitro DNase I footprinting confirmed that both sites are genuine binding sites, and cexEp::lacZ reporters demonstrated that CfaD is required for the expression of cexE in vivo. The amino terminus of CexE contains a secretory signal peptide that is removed during translocation across the cytoplasmic membrane through the general secretory pathway. These studies suggest that CexE may be a novel ETEC virulence factor because its expression is controlled by the virulence regulator CfaD, and its distribution is restricted to ETEC.