| Description | Secretion of virulence factors in Gram-negative bacteria involves transportation of the protein across two membranes to reach the cell exterior. There have been four secretion systems described in animal enteropathogens, such as Salmonella and Yersinia, with further sequence similarities in plant pathogens like Ralstonia and Erwinia [].The type III secretion system is of great interest, as it is used to transport virulence factors from the pathogen directly into the host cell and is only triggered when the bacterium comes into close contact with the host. The protein subunits of the system are very similar to those of bacterial flagellar biosynthesis. However, while the latter forms a ring structure to allow secretion of flagellin and is an integral part of the flagellum itself [ ], type III subunits in the outer membrane translocate secreted proteins through a channel-like structure.Exotoxins secreted by the type III system do not possess a secretion signal, and are considered unique for this reason [ ]. Yersinia secrete a Rho GTPase-activating protein, YopE [, ], that disrupts the host cell actin cytoskeleton. YopE is regulated by another bacterial gene, SycE [], that enables the exotoxin to remain soluble in the bacterial cytoplasm. A similar protein, exoenzyme S from Pseudomonas aeruginosa, has both ADP-ribosylation and GTPase activity [, ]. This entry also includes ADP-ribosyltransferase toxin AexT from Aeromonas salmonicida that is directly involved in the toxicity for RTG-2 (rainbow trout gonad) fish cells [].This entry also includes Exoenzyme T (ExoT) from Pseudomonas aeruginosa. ExoT contains an N-terminal GTPase-activating protein (GAP) domain and a C-terminal ADP-ribosyltransferase (ADPRT) domain. Its ADPRT domain induces atypical anoikis by transforming an innocuous cellular protein, Crk, into a cytotoxin, which interferes with integrin survival signaling. Its GAP domain activity induces mitochondrial disruption in the target host cell by activating host caspases 3 and 9 that execute cellular death [ ]. | Name | Type III secretion system effector protein YopE-like |
| Short Name | YopE-like | Type | Family |
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