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Publication Abstract from PubMed

Colicin M (ColM), which is produced by some Escherichia coli strains to kill competitor strains from the same or related species, was recently shown to inhibit cell-wall peptidoglycan biosynthesis through enzymatic degradation of its lipid II precursor. ColM-producing strains are protected against the toxin they produce by co-expression of a specific immunity protein, named Cmi, whose mode of action still remains to be identified. We here report the resolution of the crystal structure of Cmi, which is composed of 4 beta-strands and 4 alpha-helices. This rather compact structure revealed a disulfide bond between residues Cys31 and Cys107. Interestingly, these two cysteines and several other residues appeared as conserved in the sequences of several proteins of unknown function, belonging to the YebF family, which exhibit 25-35% overall sequence similarity with Cmi. Site-directed mutagenesis was performed to assess the role of these residues in the ColM immunity-conferring activity of Cmi, which showed that the disulfide bond and residues from the C-terminal extremity of the protein were functionally essential. The involvement of DsbA oxidase in the formation of the Cmi disulfide bond is also demonstrated.

X-ray structure and site-directed mutagenesis analysis of the Escherichia coli colicin M immunity protein.,Gerard F, Brooks MA, Barreteau H, Touze T, Graille M, Bouhss A, Blanot D, van Tilbeurgh H, Mengin-Lecreulx D J Bacteriol. 2010 Oct 29. PMID:21037007^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.