Biosynthesis of the antibiotic tropodithietic acid by the marine bacterium Phaeobacter inhibens

Lantibiotics are ribosomally synthesized and post-translationally modified antimicrobial peptides containing thioether rings. In addition to these crosslinks, the clinical candidate lantibiotic NAI-107 also possesses a C-terminal S-[(Z)-2-aminovinyl]-D-cysteine (AviCys) and a unique 5-chloro-L-tryptophan (ClTrp) moiety linked to its potent bioactivity. Bioinformatic and genetic analyses on the NAI-107 biosynthetic gene cluster identified mibH and mibD encoding flavoenzymes responsible for the formation of ClTrp and AviCys, respectively. The biochemical basis for the installation of these modifications on NAI-107 and the substrate specificity of either enzyme is currently unknown. Using a combination of mass spectrometry, liquid chromatography, and bioinformatic analyses we demonstrate that MibD is an FAD-dependent Cys decarboxylase and that MibH is an FADH2-dependent Trp halogenase. Most FADH2-dependent Trp halogenases halogenate free Trp, but MibH was only active when Trp was embedded within its cognate peptide substrate deschloro NAI-107. Structural comparison of the 1.85-Å resolution crystal structure of MibH with other flavin-dependent Trp halogenases revealed that subtle amino acid differences within the MibH substrate binding site generates a solvent exposed crevice presumably involved in determining its unusual substrate specificity.

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“…For both cases, these HFCD enzymes are predicted to catalyze key biosynthetic oxidative sulfur transformations. 36, 37 …”

Section: Resultsmentioning

confidence: 99%

Two Flavoenzymes Catalyze the Post-Translational Generation of 5-Chlorotryptophan and 2-Aminovinyl-Cysteine during NAI-107 Biosynthesis

et al. 2017

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“…The biosynthetic pathway of TDA has not been fully elucidated (Brock, Nikolay & Dickschat, 2014). Both labelling (Cane, Wu & Van Epp, 1992; Thiel et al, 2010) and genetic dissection (Geng & Belas, 2010) studies have shown that its aromatic skeleton is derived from phenylacetyl-CoA produced by the shikimate pathway.…”

Section: Discussionmentioning

confidence: 99%

Isolation of an antimicrobial compound produced by bacteria associated with reef-building corals

Raina

Tapiolas

Motti

et al. 2016

PeerJ

130

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Bacterial communities associated with healthy corals produce antimicrobial compounds that inhibit the colonization and growth of invasive microbes and potential pathogens. To date, however, bacteria-derived antimicrobial molecules have not been identified in reef-building corals. Here, we report the isolation of an antimicrobial compound produced by Pseudovibrio sp. P12, a common and abundant coral-associated bacterium. This strain was capable of metabolizing dimethylsulfoniopropionate (DMSP), a sulfur molecule produced in high concentrations by reef-building corals and playing a role in structuring their bacterial communities. Bioassay-guided fractionation coupled with nuclear magnetic resonance (NMR) and mass spectrometry (MS), identified the antimicrobial as tropodithietic acid (TDA), a sulfur-containing compound likely derived from DMSP catabolism. TDA was produced in large quantities by Pseudovibrio sp., and prevented the growth of two previously identified coral pathogens, Vibrio coralliilyticus and V. owensii, at very low concentrations (0.5 μg/mL) in agar diffusion assays. Genome sequencing of Pseudovibrio sp. P12 identified gene homologs likely involved in the metabolism of DMSP and production of TDA. These results provide additional evidence for the integral role of DMSP in structuring coral-associated bacterial communities and underline the potential of these DMSP-metabolizing microbes to contribute to coral disease prevention.

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“…[12,30] Besides the already known occurrence in P. gallaeciensis CIP 105210, tropone was also found in Phaeobacter sp.I8.25 and Loktanellak oreensis II 4.36.…”

Section: Other Compoundsmentioning

confidence: 94%

Homoserine Lactones, Methyl Oligohydroxybutyrates, and Other Extracellular Metabolites of Macroalgae‐Associated Bacteria of the Roseobacter Clade: Identification and Functions

et al. 2015

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Twenty-four strains of marine Roseobacter clade bacteria were isolated from macroalgae and investigated for the production of quorum-sensing autoinducers, N-acylhomoserine lactones (AHLs). GC/MS analysis of the extracellular metabolites allowed us to evaluate the release of other small molecules as well. Nineteen strains produced AHLs, ranging from 3-OH-C10:0-HSL (homoserine lactone) to (2E,11Z)-C18:2-HSL, but no specific phylogenetic or ecological pattern of individual AHL occurrence was observed when cluster analysis was performed. Other identified compounds included indole, tropone, methyl esters of oligomers of 3-hydroxybutyric acid, and various amides, such as N-9-hexadecenoylalanine methyl ester (9-C16:1-NAME), a structural analogue of AHLs. Several compounds were tested for their antibacterial and antialgal activity on marine isolates likely to occur in the habitat of the macroalgae. Both AHLs and 9-C16:1-NAME showed high antialgal activity against Skeletonema costatum, whereas their antibacterial activity was low.

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Biosynthesis of the antibiotic tropodithietic acid by the marine bacterium Phaeobacter inhibens

Abstract: The biosynthesis of tropodithietic acid was investigated using a combinatorial approach of feeding experiments, gene knockouts and bioinformatic analyses. The mechanism of sulfur introduction is distinct from known mechanisms in holomycin, thiomarinol A and gliotoxin biosynthesis.

Cited by 77 publications

References 21 publications

Two Flavoenzymes Catalyze the Post-Translational Generation of 5-Chlorotryptophan and 2-Aminovinyl-Cysteine during NAI-107 Biosynthesis

Two Flavoenzymes Catalyze the Post-Translational Generation of 5-Chlorotryptophan and 2-Aminovinyl-Cysteine during NAI-107 Biosynthesis

Isolation of an antimicrobial compound produced by bacteria associated with reef-building corals

Homoserine Lactones, Methyl Oligohydroxybutyrates, and Other Extracellular Metabolites of Macroalgae‐Associated Bacteria of the Roseobacter Clade: Identification and Functions

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