Genetic and Molecular characterization of small protein B of E coli and its implication on transcriptional regulation

Abstract

The hunt for new classes of antibiotics has been fuelled by the discovery and quick horizontal spread of antibiotic-resistant characteristics in bacteria with therapeutic relevance to humans and animals. Trans-translation is the most important and complex quality control technique for dealing with this issue, which would otherwise result in inefficient or even hazardous protein production. Because trans-translation is missing in eukaryotes yet required for bacterial fitness or survival, it is an interesting and viable target for novel antibiotics. SmpB is one of the small proteins found in almost all bacterial species and it plays a very crucial role in delivering tm-RNA s action during ribosome rescue. Extensive research on these small molecules (SsrA andamp; SmpB) has expanded their role beyond ribosome rescue. A novel role for SsrA in Mitomycin Cspecific DNA damage repair in E. coli has been reported. Here we report for the first time that over-expressed SmpB induces toxicity in the host cells. Moreover, the toxicity is dependent on the growth stage of the host cell indicating the fact that the toxicity is only bacteriostatic and not bacteriocidal. We have also shown that extensive cell filamentation is the basic cause of SmpB-mediated toxicity. The introduction of a null mutation in SulA did not reverse the SmpB-mediated filamentation which confirms the fact that the toxicity might involve SulA-independent filamentation. Further investigation into this aspect might reveal the close connection between the trans translation system and DNA damage repair pathways. The results of this investigation and its implications will be discussed highlighting the novel antimicrobial activity of SmpB in E. coli MG1655 . newline