A NOVEL ESPA-ASSOCIATED SURFACE ORGANELLE OF ENTEROPATHOGENIC ESCHERICHIA-COLI INVOLVED IN PROTEIN TRANSLOCATION INTO EPITHELIAL-CELLS

Enteropathogenic Escherichia coli (EPEC), like among bacterial pathoge ns, employ a type WI secretion system to deliver effector proteins acr oss the bacterial cell, In EPEC, four proteins are known to be exporte d by a type III secretion system-EspA, EspB and EspD required for subv ersion of host sell signal transduction pathways and a translocated in timin receptor (Tir) protein (formerly Hp90) which is tyrosine-phospho rylated following transfer to the host cell to become a receptor for i ntimin-mediated intimate attachment and 'attaching and effacing' (A/E) lesion formation, The structural basis for protein translocation has yet to Pre fully elucidated for any type III secretion system. Here, w e describe a novel EspA-confirming filamentous organelle that is prese nt on the bacterial surface during the early stage of A/E lesion forma tion, forms a physical bridge between the bacterium and the infected e ukaryotic cell surface and is required for the translocation of EspB i nto infected epithelial cells.