1. Ala(0)-actagardine, a new lantibiotic from cultures of Actinoplanes liguriae ATCC 31048
L Vértesy, W Aretz, A Bonnefoy, E Ehlers, M Kurz, A Markus, M Schiell, M Vogel, J Wink, H Kogler J Antibiot (Tokyo). 1999 Aug;52(8):730-41. doi: 10.7164/antibiotics.52.730.
The actagardine-producing strain Actinoplanes liguriae ATCC 31048, forms an additional lantibiotic when it is cultured on mannitol and soya meal. The new compound, Ala(0)-actagardine (1), has been isolated by solid-phase extraction followed by a two-step chromatographic separation. The molecular formula of 1 is C84H129N21O25S4. Its chemical structure was determined by 2D-NMR analysis and was further confirmed by an amino acid analysis, Edman degradation, and partial synthesis from actagardine. 1 exhibits a slightly higher biological activity than the parent compound actagardine. The synthetic analogs Lys(0)-actagardine (2) and Ile(0)-actagardine (3) demonstrate also antibacterial activities and emphasize the importance of the N-terminus for further derivatization.
2. Heterologous production of the lantibiotic Ala(0)actagardine in Escherichia coli
Yanxiang Shi, Alejandro Bueno, Wilfred A van der Donk Chem Commun (Camb). 2012 Nov 18;48(89):10966-8. doi: 10.1039/c2cc36336d.
We report the heterologous production of Ala(0)actagardine in E. coli by co-expression of the substrate peptide GarA and its modification enzymes GarM and GarO. The activity of GarO, a luciferase-like monooxygenase that introduces the unique sulfoxide group of actagardine, was also investigated in vitro.
3. Generation of an actagardine A variant library through saturation mutagenesis
Steven Boakes, Tania Ayala, Mark Herman, Antony N Appleyard, Michael J Dawson, Jesús Cortés Appl Microbiol Biotechnol. 2012 Sep;95(6):1509-17. doi: 10.1007/s00253-012-4041-0. Epub 2012 Apr 19.
The lantibiotic actagardine A is nineteen amino acids in length and comprises three intertwined C-terminal methyllanthionine-bridged rings and an N-terminal lanthionine-bridged ring. Produced by the actinomycete Actinoplanes garbadinensis ATCC 31049, actagardine A demonstrates antibacterial activity against important Gram-positive pathogens. This activity combined with its ribosomal synthesis makes it an attractive target for the generation of lantibiotic variants with improved biological activity. A variant generation system designed to allow the specific substitution of amino acids at targeted sites throughout the actagardine A peptide has been used to generate a comprehensive library by site-directed mutagenesis. With the exception of residues involved in bridge formation, each amino acid in the actagardine A peptide as well as the alanine (ala(0)) at position -1 relative to the mature peptide, has been systematically substituted with all remaining 19 amino acids. A total of 228 mutants have been engineered with 44 produced in good yield. The mutant V15F in particular demonstrates improved activity against a range of notable Gram-positive pathogens including Clostridium difficile, when evaluated alongside actagardine A. The scope of variants generated provides an insight into the flexibility of the actagardine A processing machinery and will undoubtedly assist in future mutational studies.
