Synthesis and functioning of the colicin El lysis protein: comparison with the colicin A lysis protein

The colicin El lysis protein, CelA, was identified as a 3-kDa protein in induced cells of Escherichia coli K-12 carrying pColEl by pulse-chase labeling with either [35S]cysteine or [3lH]lysine. This 3-kDa protein was acylated, as shown by [2-3H]glycerol labeling, and seemed to correspond to the mature CelA protein. The rate of modification and processing of CelA was different from that observed for Cal, the colicin A lysis protein. In contrast to Cal, no intermediate form was detected for CelA, no signal peptide accumulated, and no modified precursor form was observed after globomycin treatment. Thus, the rate of synthesis would not be specific to lysis proteins. Solubilization in sodium dodecyl sulfate of the mature forms of both CeIA and Cal varied similarly at the time of colicin release, indicating a change in lysis protein structure. This particular property would play a role in the mechanism of colicin export. The accumulation of the signal peptide seems to be a factor determining the toxicity of the lysis proteins since CelA provoked less cell damage than Cal. Quasi-lysis and killing due to CelA were higher in degP mutants than in wild-type cells. They were miniimal in pidA mutants. Colicin lysis proteins are small lipoproteins that allow the release of colicins by strains of Escherichia coli carrying a colicinogenic plasmid. In contrast to colicins, which diffe