Bacteria contain an important regulatory pathway involving a unique RNA molecule (tmRNA, SsrA RNA, 10Sa RNA) and an associated cofactor SmpB. Its main roles entail clearing stalled ribosomes and marking the resulting truncated polypeptide for degradation by either cytoplasmic or periplasmic proteases. While tmRNA is not necessary for the survival of all bacteria under laboratory conditions, this regulatory system, in theory, would be vital for infectious bacteria under the adverse conditions of their host where errors leading to ribosomal stalling are more likely.
This study determines the survival significance of the SsrA-SmpB system in Yersinia pestis, the causative agent of plague and an emerging threat in bioterrorism, and identifies the genes expressed during infection. SsrA/SmpB and SmpB gene knockouts are introduced into the Yersinia genome and cell growth is compared in a normal culture and an infectious environment. In addition, a His6 site-directed mutagenesis in the coding sequence of the SsrA proteolytic tag is introduced into the Yersinia pestis genome. Immunochemical methods facilitate a functional endogenous protein tagging assay after exposure to the normal cell culture as well as the infectious environment within macrophages. The results, however, are still pending.