Stephanie Helbig

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Colicin M (Cma) is specifically imported into the periplasm of Escherichia coli and kills the cells. Killing depends on the periplasmic peptidyl prolyl cis-trans isomerase/chaperone FkpA. To identify the Cma prolyl bonds targeted by FkpA, we replaced the 15 proline residues individually with alanine. Seven mutant proteins were fully active; Cma(P129A),(More)
Colicin M (Cma) lyses Escherichia coli cells by inhibiting murein biosynthesis through hydrolysis of the phosphate ester between C(55)-polyisoprenol and N-acetylmuramyl (MurNAc)-pentapeptide-GlcNAc in the periplasm. To identify Cma functional domains, we isolated 54 point mutants and small deletion mutants and examined their cytotoxicity levels. Activity(More)
Colicins are the only proteins imported by Escherichia coli and thus serve as tools to study the protein import mechanism. Most of the colicins studied degrade DNA, 16S RNA or tRNA in the cytoplasm, or form pores in the cytoplasmic membrane. Two bacteriocins, Cma (colicin M) and Pst (pesticin), affect the murein structure in the periplasm. These two(More)
Colicin M (Cma) is a protein toxin produced by Escherichia coli that kills sensitive E. coli cells by inhibiting murein biosynthesis in the periplasm. Recombinant plasmids carrying cbrA (formerly yidS) strongly increased resistance of cells to Cma, whereas deletion of cbrA increased Cma sensitivity. Transcription of cbrA is positively controlled by the(More)
The paper provides a short overview of three investigated bacterial protein toxins, colicin M (Cma) of Escherichia coli, pesticin (Pst) of Yersinia pestis and hemolysin (ShlAB) of Serratia marcescens. Cma and Pst are exceptional among colicins in that they kill bacteria by degrading the murein (peptidoglycan). Both are released into the medium and bind to(More)
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