Biosynthesis and secretion of a precursor of nisin Z by Lactococcus lactis, directed by the leader peptide of the homologous lantibiotic subtilin from Bacillus subtilis.

The DNA sequence encoding the leader peptide of the lantibiotic subtilin from Bacillus subtilis was fused to the sequence encoding pronisin Z, and this hybrid gene was expressed in a Lactococcus lactis strain that produces nisin A. This strain simultaneously secreted nisin A and a protein of approximately 6 kDa. Amino acid sequencing of the purified 6 kDa protein and structural analysis of its main tryptic fragment by two-dimensional 1H-NMR showed that it consists of the unmodified leader peptide of subtilin, without the N-terminal methionine residue, linked to a fully matured nisin Z part. The hybrid protein and its main tryptic fragment [ITPQ]-nisin Z, showed at least 200-fold lower antimicrobial activities than nisin Z against three different indicator strains.