Probable detection of kil peptide derived from colicin E1 plasmid in the envelope fraction of Escherichia coli HB101 carrying pEAP31.

Escherichia coli carrying plasmid pEAP31 produces extracellularly alkalophilic Bacillus penicillinase encoded on the plasmid. The extracellular production has been suggested to be caused by activation of dormant colicin E1 kil gene. Two peptides that could be respectively precursor and mature products of colicin E1 kil gene were detected on an SDS/polyacrylamide gel. One of the peptides (Mr 4800), which was probably a precursor peptide, was detected in the inner-membrane fraction from the organism when envelope proteins were subjected to differential solubilization. The other (Mr 3500), which was a mature peptide, was detected in the outer-membrane fraction of the organism. The mature peptide was only detected in the envelope of cells releasing the penicillinase transiently accumulated in the periplasm into the culture medium.