YaxAB, a Yersinia enterocolitica Pore-Forming Toxin Regulated by RovA

Abstract

ABSTRACTThe transcriptional regulator RovA positively regulates transcription of theYersinia enterocoliticavirulence geneinv. Invasin, encoded byinv, is important for establishment ofY. enterocoliticainfection. However, arovAmutant is more attenuated for virulence than aninvmutant, implying that RovA regulates additional virulence genes. When theY. enterocoliticaRovA regulon was defined by microarray analysis, YE1984 and YE1985 were among the genes identified as being upregulated by RovA. Since these genes are homologous toXenorhabdus nematophilacytotoxin genesxaxAandxaxB, we named themyaxAandyaxB, respectively. In this work, we demonstrate the effects of YaxAB on the course of infection in the murine model. While ayaxABmutant (ΔyaxAB) is capable of colonizing mice at the same level as the wild type, it slightly delays the course of infection and results in differing pathology in the spleen. Further, we found thatyaxABencode a probable cytotoxin capable of lysing mammalian cells, that both YaxA and YaxB are required for cytotoxic activity, and that the two proteins associate. YaxAB-mediated cell death occurs via osmotic lysis through the formation of distinct membrane pores.In silicotertiary structural analysis identified predicted structural homology between YaxA and proteins in pore-forming toxin complexes fromBacillus cereus(HBL-B) andEscherichia coli(HlyE). Thus, it appears that YaxAB function as virulence factors by inducing cell lysis through the formation of pores in the host cell membrane. This characterization of YaxAB supports the hypothesis that RovA regulates expression of multiple virulence factors inY. enterocolitica.