Effect of leader peptide mutations on biosynthesis of the lantibiotic Pep5

Lantibiotics are lanthionine-containing antibiotic peptides which are synthesized from ribosomal prepeptides by post-translational modification. In order to elucidate the function of a conserved motif in the N-terminal leader sequence of lantibiotic prepeptides, three amino acids were exchanged in the leader peptide sequence of the lantibiotic Pep5. Exchanging Phe-19 for Ser and Glu-16 for Lys in the FDLEI-motif, reduced Pep5 production to 35 and 38% of the control whereas, after exchanging Asp-6 for Lys, the production was decreased only to 82%. Proteolytic fragments of Pep5 or incorrectly modified Pep5 molecules, indicative of incorrect modifications, were not found in the culture supernatant. Thus, in contrast to the biosynthesis of the lantibiotic nisin, the FDLEI-motif is not essential for biosynthesis of Pep5 and has no influence on correct ring formation or processing, but seems to be important for optimal biosynthesis rates.