Proteomics approach on the identification of virulence factors of enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) and further characterization of two effectors: EspB and NleI

Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) are two closely related human pathogens responsible for food-borne epidemics in many countries. Several virulence factors together with some putative proteins were identified from the extracellular proteomes of EPEC and EHEC. One of the major secreted proteins, EspB, was found to have two dominant forms in extracellular proteomics profiles of EPEC and EHEC. EspB was shown to be translocated into the host cells by TTSSs and was indicated to be a TTSS encoded effector. Furthermore, a novel effector, NleI, was identified from EPEC sepL and sepD mutants by comparative proteomics. The expression of NleI was found to be regulated by SepD at the transcriptional level. NleI was demonstrated to be translocated into HeLa cells in a TTSS dependent manner. Using sub-cellular fractionation and fluorescence microscopy, NleI was shown to be localized in HeLa cell membrane and cytosol without obvious cytotoxic effect.

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• EPEC, EHEC, proteomics, type III secretion system, effector, virulence factor