Figure 4

Site directed mutagenesis of the structural backbone of the lantibiotic peptide LtnA1. Mutants N15K, A17N and L21A are indicated by arrows. Well diffusion assays indicating the activity (AU/ml) of concentrated purified supernatants of the mutants (Varian C18 column) and mass spectrometry profiles accompany each mutant generated. The scale on the y-axis of the mass-spec is L21A: 2000–3700 mass/charge, A17N: 2700–3400 mass/charge, N15K: 2000–3600 mass/charge. The Mutant L21A has no activity (0 AU/ml), the + indicates that this mutant was combined with LtnA1 and LtnA2, and a complementation effect was evident with LtnA1. The mutant A27S could not be generated but represents the fourth amino acid difference between staphylococcin C55α and LtnA1. The shaded broken circle represents the putative lipid II binding region of LtnA1.