Post-translational regulation of Lcr plasmid-mediated peptides in pesticinogenic Yersinia pestis.

The low calcium response of wild type Yersinia pestis, the causative agent of bubonic plague, and of enteropathogenic Yersinia pseudotuberculosis and Yersinia enterocolitica is known to be mediated by a shared Lcr plasmid of about 70 kb. At 37 degrees C in Ca2+-deficient medium, this element promotes restriction of growth with concomitant production of virulence functions including the common V antigen and a set of yersiniae outer membrane peptides termed YOPs (Lcr+). The latter are expressed by the enteropathogenic species but not by wild type Y. pestis which possesses a unique 10 kb Pst plasmid associated with pesticinogeny (Pst+). We show in this report that, after pulse with 35S-methionine, peptides with molecular weights corresponding to YOPs of 78, 47, 45, 44, 36, and 26 kDa are synthesized during the low calcium response by both Lcr+, Pst+ and Lcr+, Pst- cells of Y. pestis. Although stable in the latter, radioactivity in YOPs of wild type was rapidly chased into lower molecular weight degradation products. At least four soluble peptides, including V, were also labeled during starvation for Ca2+; these structures were stable in both Lcr+, Pst+ and Lcr+, Pst- yersiniae. These findings suggest that a product encoded by the Pst plasmid of Y. pestis is required for post-translational regulation of outer membrane but not soluble peptides mediated by a second unrelated Lcr plasmid.