In vitro expression of a 22-kilodalton Yersinia pestis polypeptide immunologically related to the 25-kilodalton plasmid-encoded protein of the three pathogenic Yersinia species

Expression of the plague plasminogen activator in Yersinia pseudotuberculosis and Escherichia coli

Enteropathogenic yersiniae (Yersinia pseudotuberculosis and Yersinia enterocolitica) typically cause chronic disease as opposed to the closely related Yersinia pestis, the causative agent of bubonic plague. It is established that this difference reflects, in part, carriage by Y. pestis of a unique 9.6-kb pesticin or Pst plasmid (pPCP) encoding plasminogen activator (Pla) rather than distinctions between shared approximately 70-kb low-calcium-response, or Lcr, plasmids (pCD in Y. pestis and pYV in enteropathogenic yersiniae) encoding cytotoxic Yops and anti-inflammatory V antigen. Pla is known to exist as a combination of 32.6-kDa (alpha-Pla) and slightly smaller (beta-Pla) outer membrane proteins, of which at least one promotes bacterial dissemination in vivo and degradation of Yops in vitro. We show here that only alpha-Pla accumulates in Escherichia coli LE392/pPCP1 cultivated in enriched medium and that either autolysis or extraction of this isolate with 1.0 M NaCl results in release of soluble alpha and beta forms possessing biological activity. This process also converted cell-bound alpha-Pla to beta-Pla and smaller forms in Y. pestis KIM/pPCP1 and Y. pseudotuberculosis PB1/+/pPCP1 but did not promote solubilization. Pla-mediated posttranslational hydrolysis of pulse-labeled Yops in Y. pseudotuberculosis PB1/+/pPCP1 occurred more slowly than that in Y. pestis but was otherwise similar except for accumulation of stable degradation products of YadA, a pYV-mediated fibrillar adhesin not encoded in frame by pCD. Carriage of pPCP by Y. pseudotuberculosis did not significantly influence virulence in mice.

Identification of additional virulence determinants on the pYV plasmid of Yersinia enterocolitica W227

This paper describes the mutagenesis of the pYV plasmid from Yersinia enterocolitica W22703 (serotype O:9) with Tn2507, a new element generating operon fusions. Analysis of the mutants allowed the identification of an additional Yop protein called Yop20 and the mapping of yop20, yop44, yop48, and lcrV, the gene encoding the V antigen. The last gene appeared to be part of an operon that also may contain yop37 and yop44. At 37 degrees C, mutants affected in this operon grew poorly, irrespective of the presence of Ca2+, or they even died in the presence of Ca2+. This operon is thus involved in the regulation by Ca2+, and we called it car, for Ca2+ regulation. It is presumably the Y. enterocolitica counterpart of the lcrGVH operon of Yersinia pestis. Transcription of yop20 and of the car operon was strongly regulated by temperature and only slightly by calcium. Hence, these genes behaved like the other genes of the yop regulon. Mutants affected in yop20 or in yop48 were markedly less virulent for the desferrioxamine-treated mouse than was the parental strain. Yop20 and Yop48 thus probably are Yersinia virulence factors.

Expression of the low calcium response in Yersinia pestis

Pathogenic yersiniae undergo an established low calcium response (LCR) at 37 degrees C in Ca2+-deficient media characterized by restricted growth with synthesis of Lcr plasmid-encoded virulence functions. The latter include outer membrane peptides (Yops) known to undergo Pst plasmid-mediated post-translational degradation in Yersinia pestis but not in enteropathogenic yersiniae lacking this plasmid. Salient Yops of Y. pestis are shown here to be either maintained in the steady state or to exist as a stable degradation product (p24 of Yop E). Processing of plague plasminogen activator (p36 to p33), responsible for hydrolysis of Yops, required 2 h. Avirulence of mutants with inserted Mu dl1 (Apr lac) in yopE was verified and shown to occur independently of introduced fusion-dependent peptides. However, avirulence of such yopE mutants but not that of isolates lacking the Lcr plasmid was phenotypically suppressed in mice injected with iron. Appearance of 20,500 and 40,500 Da heat-shock peptides preceded onset of the LCR. Lcr plasmid mediated V antigen (p38) and p20, Pst plasmid-encoded p36, and chromosomally promoted p56 and p70 were synthesized throughout the LCR. Classical antigen 5 was equated with p70 which was shared by Yersinia pseudotuberculosis but not Yersinia enterocolitica.