ABSTRACTEpsC, one of the components comprising the type II secretion system (T2SS), was isolated from a human-pathogenic bacterium,Vibrio vulnificus, to evaluate its role in eliciting virulence. AnespC-deleted mutant ofV. vulnificusdisplayed a reduced cytotoxicity to the human cell line HEp-2 and an attenuated virulence in a mouse model. This mutant exhibited dramatic defects in the secretion of diverse extracellular proteins, such as outer membrane proteins, transporters, and the known secreted factors, notably, a hemolysin (VvhA) and an elastase (VvpE). A defect in its secretion of proteins was restored by intranscomplementation of the intactepsCgene. Analyses of cellular fractions revealed that VvhA and VvpE of theΔepsCmutant were not excreted outside the cell but were present mainly in the periplasmic space. Examination of aV. vulnificusmutant deficient in TolC, a component of the T1SS, showed that it is not involved in the secretion of VvhA and VvpE but that it is necessary for the secretion of another major toxin ofV. vulnificus, RtxA. Therefore, the T2SS is required forV. vulnificuspathogenicity, which is mediated by at least two secreted factors, VvhA and VvpE, via facilitating the secretion and exposure of these factors to host cells.
Crystal structure of the full-length ATPase GspE from the Vibrio vulnificus type II secretion system in complex with the cytoplasmic domain of GspL
