Abstract
BackgroundLike many other pathogens, enterohaemorrhagic and enteropathogenic strains of Escherichia coli employ a type-III secretion system to translocate bacterial effector proteins into host cells, where they then disrupt a range of cellular functions. This system is encoded by the locus for enterocyte effacement. Many of the genes within this locus have been assigned names and functions through homology with the better characterised Ysc-Yop system from Yersinia spp. However, the functions and homologies of many LEE genes remain obscure.ResultsWe have performed a fresh bioinformatics analysis of the LEE. Using PSI-BLAST we have been able to identify several novel homologies between LEE-encoded and Ysc-Yop-associated proteins: Orf2/YscE, Orf5/YscL, rORF8/EscI, SepQ/YscQ, SepL/YopN-TyeA, CesD2/LcrR. In addition, we highlight homology between EspA and flagellin, and report many new homologues of the chaperone CesT.ConclusionWe conclude that the vast majority of LEE-encoded proteins do indeed possess homologues and that homology data can be used in combination with experimental data to make fresh functional predictions.
Highlights
Like many other pathogens, enterohaemorrhagic and enteropathogenic strains of Escherichia coli employ a type-III secretion system to translocate bacterial effector proteins into host cells, where they disrupt a range of cellular functions
Type-III secretion systems can be classified into two major groups: those associated with flagellar biosynthesis and those associated with interactions between bacteria and eukaryotic cells [5]
We conclude that the vast majority of LEE-encoded proteins do possess homologues and that homology data can be used in combination with experimental data to make fresh functional predictions (Figure 1, Table 1)
Summary
Enterohaemorrhagic and enteropathogenic strains of Escherichia coli employ a type-III secretion system to translocate bacterial effector proteins into host cells, where they disrupt a range of cellular functions. The important human pathogens, enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC respectively) utilise type-III secretion to subvert eukaryotic signalling pathways by injecting bacterial effector proteins into the host cell cytoplasm [1,9,10,11,12]. Within these pathovars, a well-characterised T3SS is responsible for the development of a characteristic attaching-effacing (AE) lesion and for other effects on enterocyte function [9,11,12,13]
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