Acquisition of omptin reveals cryptic virulence function of autotransporter YapE in Y ersinia pestis

Summary Autotransporters, the largest family of secreted proteins in G ram‐negative bacteria, perform a variety of functions, including adherence, cytotoxicity and immune evasion. In Y ersinia pestis the autotransporter YapE has adhesive properties and contributes to disease in the mouse model of bubonic plague. Here, we demonstrate that omptin cleavage of Y . pestis   YapE is required to mediate bacterial aggregation and adherence to eukaryotic cells. We demonstrate that omptin cleavage is specific for the Y . pestis and Y . pseudotuberculosis   YapE orthologues but is not conserved in the Y ersinia enterocolitica protein. We also show that cleavage of YapE occurs in Y . pestis but not in the enteric Y ersinia species, and requires the omptin Pla (plasminogen activator protease), which is encoded on the Y . pestis ‐specific plasmid pPCP 1. Together, these data show that post‐translation modification of YapE appears to be specific to Y . pestis , was acquired along with the acquisition of pPCP 1 during the divergence of Y . pestis from Y . pseudotuberculosis , and are the first evidence of a novel mechanism to regulate bacterial adherence.