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Appl. Environ. Microbiol., 02 1996, 385-392, Vol 62, No. 2
G Bierbaum, C Szekat, M Josten, C Heidrich, C Kempter, G Jung and HG Sahl
Pep5 is a 34-amino-acid antimicrobial peptide, produced by Staphylococcus
epidermidis 5, that contains the thioether amino acids lanthionine and
methyllanthionine, which form three intramolecular ring structures. In
addition, two didehydrobutyrines are present in the central part of the
lantibiotic and an oxobutyryl residue is located at the N terminus. All
rare amino acids are introduced by posttranslational modifications of a
ribosomally made precursor peptide. To elucidate the function of the
modified residues for the antimicrobial action of Pep5, mutant peptides, in
which single modified residues had been eliminated, were produced by
site-directed mutagenesis. All of these peptides showed a reduced
antimicrobial activity. In addition, those peptides from which the ring
structures had been deleted became susceptible to proteolytic digest. This
demonstrates that the ring structures serve as stabilizers of conformations
essential for activity, e.g., amphiphilicity, as well as for protecting
Pep5 against proteases of the producing strains. In addition, residues that
could serve as precursors of new modified amino acids in lantibiotics were
introduced into the Pep5 precursor peptide. This way, a novel
methyllanthionine and a didehydroalanine were inserted into the flexible
central part of Pep5, demonstrating that biosynthesis of modified amino
acids is feasible by protein engineering and use of the lantibiotic
modification system.
Copyright © 1996, American Society for Microbiology
Engineering of a novel thioether bridge and role of modified residues in the lantibiotic Pep5
Institut fur Medizinische Mikrobiologie und Immunologie der Universitat Bonn, Germany.
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