Abstract
Enterohemorrhagic E. coli (EHEC) causes severe diseases in humans worldwide. One of its virulence factors is EspP, which belongs to the serine protease autotransporters of Enterobacteriaceae (SPATE) family. In this review we recapitulate the current data on prevalence, biogenesis, structural properties and functionality. EspP has been used to investigate mechanistic details of autotransport, and recent studies indicate that this transport mechanism is not autonomous but rather dependent on additional factors. Currently, five subtypes have been identified (EspPα-EspPε), with EspPα being associated with highly virulent EHEC serotypes and isolates from patients with severe disease. EspPα has been shown to degrade major proteins of the complement cascade, namely C3 and C5 and probably interferes with hemostasis by cleavage of coagulation factor V. Furthermore, EspPα is believed to contribute to biofilm formation perhaps by polymerization to rope-like structures. Together with the proteolytic activity, EspPα might ameliorate host colonization and interfere with host response.
Highlights
The plasmid-encoded extracellular serine protease EspP is one of the most abundant proteins in culture supernatants of Shiga-toxin producing Escherichia coli (STEC) and enterohemorrhagic E. coli (EHEC) [1,2] and has been first described on the large plasmid pO157 of EHEC O157:H7 strainEDL933 [1]
EHEC are pathogens that cause severe diseases in humans worldwide. Their pathogenicity is a multifactorial process and besides the well-known Shiga toxins, EHEC express a variety of further virulence factors
The espP gene is highly prevalent in EHEC and to date five EspP subtypes are known that differ in their proteolytic activity and in their ability to translocate across the bacterial cell membranes
Summary
The plasmid-encoded extracellular serine protease EspP is one of the most abundant proteins in culture supernatants of Shiga-toxin producing Escherichia coli (STEC) and enterohemorrhagic E. coli (EHEC) [1,2] and has been first described on the large plasmid pO157 of EHEC O157:H7 strain. Autotransporters show considerable structural and functional differences and include adhesins, proteases and lipases As indicated by their name, SPATEs exhibit serine protease activity and are secreted by Enterobacteriaceae. EspP/PssA (extracellular serine protease, plasmid-encoded/protein secreted by STEC A). SPATE proteins are believed to contribute to the virulence of their bacterial host by the secreted passenger domains which all harbor the serine protease motif GDSGS (with S being the catalytic serine residue). Additional virulence factors are necessary that mediate bacterial adherence or interfere with the host response [47,48] This is exemplified by strains that lack. Bacterial adherence can be mediated by other factors as observed in the European E. coli O104:H4 outbreak in 2011 This outbreak suggests that different “recipes” for high virulence do exist for this pathogen [40].
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