Observations on the conversion of an inactive precursor protein to the antibiotic nisin

Abstract

Stationary-phase cultures of Streptococcus lactis (strain 1) ere used to produce basic peptides which had no antibiotic activity but which contained material electrophoretically similar to nisin. Cells of S. lactis (strain 354/07) which produce nisin in late log phase and stationary phase were harvested in early log phase and used for preparing cell extracts (C.E.). Incubation of C.E. with basic peptide preparations from strain 1 generated an antibiotic believed to be nisin. The amount generated was directly related to one of the peak areas in the electrophoretograms of the basic peptide preparations. It is suggested that material in this peak is similar to or is a precursor of nisin. The specific activity of the C.E. was highest when a mild disruption method was used which affected neither the phase-contrast appearance nor the Gram reaction of the organism.