Phenotypic characterization of OmpX, an Ail homologue of Yersinia pestis KIM

Abstract

The goal of this study was to characterize the Yersinia pestis KIM OmpX protein. Yersinia spp. provide a model for studying several virulence processes including attachment to, and internalization by, host cells. For Yersinia enterocolitica and Yersinia pseudotuberculosis, Ail, YadA and Inv, have been implicated in these processes. In Y. pestis, YadA and Inv are inactivated. Genomic analysis of two Y. pestis strains revealed four loci with sequence homology to Ail. One of these genes, designated y1324 in the Y. pestis KIM database, encodes a protein designated OmpX. The mature protein has a predicted molecular mass of 17.47 kDa, shares approximately 70 % sequence identity with Y. enterocolitica Ail, and has an identical homologue, designated Ail, in the Y. pestis CO92 database. The present study compared the Y. pestis KIM6 + parental strain with a mutant derivative having an engineered disruption of the OmpX structural gene. The parental strain (and a merodiploid control strain) expressed OmpX at 28 and 37 6C, and the protein was detectable throughout all phases of growth. OmpX was required for efficient adherence to, and internalization by, cultured HEp-2 cell monolayers and conferred resistance to the bactericidal effect of human serum. Deletion of ompX resulted in a significantly reduced autoaggregation phenotype and loss of pellicle formation in vitro. These results suggest that Y. pestis OmpX shares functional homology with Y. enterocolitica Ail in adherence, internalization into epithelial cells and serum resistance.

TheYersinia pestisAil Protein Mediates Binding and Yop Delivery to Host Cells Required for Plague Virulence

“…Recently, the Y. pestis Ail protein was also shown to mediate cell binding, cell invasion, bacterial autoaggregation, and serum resistance (3,28). This finding was somewhat surprising, since Y. pestis Ail is nearly identical to Yersinia pseudotuberculosis Ail, which has been reported to confer serum resistance but not play a role in adhesion or invasion of tissue culture cells (67).…”

“…Genomic sequencing of three of these mutants identified the locus of the mariner insertion as the ail gene of Y. pestis (20). Ail has been defined previously in pathogenic Yersinia species as mediating cell attachment and invasion as well as serum resistance (3,28,40,67). Homologues of Ail in other genera have also been referred to as an opacity factor, since deletion of the locus results in an altered colony morphology phenotype (7).…”

The Yersinia pseudotuberculosis Outer Membrane Protein Ail Recruits the Human Complement Regulatory Protein Factor H

“…However, as the molecular mechanisms of these proteins become characterized, it is apparent that conserved functions can be assigned to several members of this family. Rck, PagC (Salmonella choleraesuis), and Ail were shown to mediate serum resistance (3-5, 23, 24), whereas adhesion and/or invasion properties have been observed in all of the aforementioned proteins, with the exception of Y. pseudotuberculosis Ail (25)(26)(27)(28)(29). Furthermore, functional fH and C4BP binding have now been described in Rck (21,30) and Y. enterocolitica and Y. pseudotuberculosis Ail (10,11,15).…”

Cronobacter sakazakii: stress survival and virulence potential in an opportunistic foodborne pathogen

“…85 However, Kim and colleagues further demonstrated that another outer membrane protein, OmpX, also plays a major role in invasion of Caco-2 epithelial cells 85 and has been shown to be necessary for the invasion of Hep-2 cells by Yersinia pestis and C. sakazakii. 86,87 As a consequence, it was observed that ompA/X deletion mutants were significantly less efficient in the dissemination of the bacterium to other organs such as the liver and spleen in vivo.…”