An unusual ring pattern in the Rosβ lanthipeptide of the two-component lantibiotic roseocin

Abstract

Two-component lantibiotics comprise two post-translationally modified peptides that synergistically exert antimicrobial activity. Most known two-component lantibiotics are made up of a structurally conserved -lanthipeptide that binds to the peptidoglycan precursor lipid II and a {beta}-lanthipeptide that is believed to interact with the -peptide-lipid II complex to form pores in the membranes of susceptible bacteria. A few two-component lantibiotics including roseocin do not follow this general scheme and act by different, currently unresolved mechanisms. An important first step in studying this group of lanthipeptides is determination of their chemical structure. Roseocins {beta}-peptide (Ros{beta}) is formed by the RosM lanthipeptide synthetase from the RosA1 precursor peptide. RosM carries out nine dehydrations of Ser and Thr residues to the corresponding dehydroamino acids followed by six Michael-type additions of the thiols of Cys residues to a subset of the dehydroamino acids forming six thioether crosslinks. Sequence alignment with structurally characterized lanthipeptides does not allow prediction of its ring pattern. In this study, Ros{beta} was produced in Escherichia coli and its ring pattern was established by multi-dimensional NMR spectroscopy. The stereochemistry of the lanthionine and methyllanthionine residues was determined by Marfeys analysis with authentic standards. Ros{beta} is shown to have a unique ring pattern amongst previously characterized lanthipeptides. TOC graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=131 SRC="FIGDIR/small/684949v2_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@125226borg.highwire.dtl.DTLVardef@f6a170org.highwire.dtl.DTLVardef@1e0e57corg.highwire.dtl.DTLVardef@1fa4c8d_HPS_FORMAT_FIGEXP M_FIG C_FIG