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 subtil in from Bacillus subtilis was fused to the sequence encoding pronisin Z, and this hybrid gene was expressed in a Lactococcus lactis strain t hat produces nisin A. This strain simultaneously secreted nisin A and a protein of approximately 6 kDa. Amino acid sequencing of the purifie d 6 kDa protein and structural analysis of its main tryptic fragment b y two-dimensional H-1-NMR showed that it consists of the unmodified le ader peptide of subtilin, without the N-terminal methionine residue, l inked to a fully matured nisin Z part. The hybrid protein and its main tryptic fragment [ITPQ]-nisin Z, showed at least 200-fold lower antim icrobial activities than nisin Z against three different indicator str ains.