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Labyrinthopeptins are class III lantibiotics produced by the actinomycete Actinomadura namibiensis. The most characteristic structural feature is the posttranslationally installed triamino triacid labionin with a quaternary α-carbon. In addition to the unique structure, labyrinthopeptin A2 possess remarkable antiviral and antiallodynic biological activities. To harness the substrate tolerance of the biosynthetic machinery, we developed an efficient system for the generation of labyrinthopeptin analogs. Streptomyces lividans was used as a heterologous host since the natural producer Actinomadura namibiensis remained genetically intractable. Generation of a library of 39 mutants allowed identification of variable and invariable regions in the labyrinthopeptin structures. Additional data on the flexibility of the biosynthetic machinery were provided by in vitro experiments. This study is detailed investigation on the potential to generate analogs of class III lantibiotics by genetic engineering., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Lantibiotics are ribosomally synthesized peptides containing post-translationally installed lanthionine thioether bridges. Recently characterized class III lantibiotics have also revealed the occurrence of labionin, a novel carbacyclic variation of lanthionine, and highlighted the structural diversity within this group. Here we describe the discovery and characterization of curvopeptins produced by Thermomonospora curvata, the first class III lantibiotics of thermophilic origin. Furthermore, investigation of the modifying enzyme CurKC and in particular the characterization of its specificity toward phosphorylation co-substrates was performed. Remarkably, all investigated NTPs and dNTPs were accepted by the enzyme, although the purine nucleotides ATP/dATP and GTP/dGTP were the preferred co-substrates. This finding complements previous studies on the class III lantibiotic synthetases LabKC and EryKC and underlines the surprising promiscuity of the Ser/Thr-kinase domain. Enzymatic studies with a precursor peptide mutant allowed the assignment of all dehydration sites and further GC-MS analysis revealed the presence of lanthionine as the main type of intramolecular ring., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Lantibiotics are a large group of ribosomally synthesized peptides post-translationally modified to incorporate the amino acid lanthionine. They are classified, according to their biosynthetic pathway and bioactivity, into three major subtypes. Of Actinomycetes type III lantibiotics, only four peptides (SapB, SapT, LabA1, and LabA2) have been described and structurally characterized, although homologous gene clusters are abundant in other Actinomycetes. All these gene clusters share a similar architecture with a characteristic Ser/Ser/Cys motif in precursor peptides, which has previously been suggested to act as a precursor for lanthionine (SapB) and labionin (LabA2) rings. Mass spectrometry screening led to the discovery and characterization of three new representatives of type III lantibiotics: Avermipeptin (Avi), Erythreapeptin (Ery), and Griseopeptin (Gri) from Streptomyces avermitilis DSM 46492, Saccharopolyspora erythraea NRRL 2338, and Streptomyces griseus DSM 40236, respectively. Apart from the assignment of these peptides to their corresponding gene clusters, additional investigations on Avi, Ery and Gri peptides indicate stepwise leader processing by putative aminopeptidase-like protease(s), thus yielding mixtures of differently N-terminal-processed lantibiotic peptides. Similar peptide processing was observed for a heterologously expressed eryth biosynthetic gene cluster expressed in a Streptomyces host system. Remarkably, all isolates of the new type III lantibiotics contain both the amino acids lanthionine and labionin, thus implying dual-mode cyclase activity of the processing lyase-kinase-cyclase enzymes. These findings have implications for the structures and maturation of other type III lantibiotics from Actinomycetes., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)