The Flavoprotein MrsD Catalyzes the Oxidative Decarboxylation Reaction Involved in Formation of the Peptidoglycan Biosynthesis Inhibitor Mersacidin

Abstract

The lantibiotic mersacidin inhibits peptidoglycan biosynthesis by binding to the peptidoglycan precursor lipid II. Mersacidin contains an unsaturated thioether bridge, which is proposed to be synthesized by posttranslational modifications of threonine residue ؉15 and the COOH-terminal cysteine residue of the mersacidin precursor peptide MrsA. We show that the flavoprotein MrsD catalyzes the oxidative decarboxylation of the COOH-terminal cysteine residue of MrsA to an aminoenethiol residue. MrsD belongs to the recently described family of homo-oligomeric flavin-containing Cys decarboxylases (i.e., the HFCD protein family). Members of this protein family include the bacterial Dfp proteins (which are involved in coenzyme A biosynthesis), eukaryotic salt tolerance proteins, and further oxidative decarboxylases such as EpiD. In contrast to EpiD and Dfp, MrsD is a FAD and not an FMN-dependent flavoprotein. HFCD enzymes are characterized by a conserved His residue which is part of the active site. Exchange of this His residue for Asn led to inactivation of MrsD. The lantibiotic-synthesizing enzymes EpiD and MrsD have different substrate specificities.Lantibiotics (for "lanthionine-containing antibiotics") are a group of ribosomally synthesized and posttranslationally modified antibiotic peptides containing the thioether amino acid lanthionine as a characteristic building block (33). In the last few years, several lantibiotics with unsaturated thioether bridges at the COOH terminus have been characterized. (2), gallidermin (12), cypemycin (27), and some of the mutacins (28-30, 34), whereas mersacidin contains a COOH-terminal S-[(Z)-2-aminovinyl]-D-cysteine is present in epidermin S-[(Z)-2-aminovinyl]-3-methyl-D-cysteine residue (15, 32).Among these lantibiotics, mersacidin, which is produced by a Bacillus strain (9), is of particular interest because it is active against methicillin-resistant Staphylococcus aureus strains (8). Brötz et al. (6,7) were able to show that mersacidin inhibits the transglycosylation reaction in peptidoglycan biosynthesis by binding to the cell wall precursor lipid II [undecaprenyldiphosphoryl-N-acetylmuramic acid-(pentapeptide)-N-acetylglucosamine]. The complex formed by mersacidin and lipid II differed from the well-known vancomycin-lipid II complex, making mersacidin to a new lead structure for the development of antimicrobial compounds. The biosynthesis of the S-[(Z)-2-aminovinyl]-D-cysteineresidue of epidermin depends on the flavoenzyme EpiD. EpiD catalyzes the oxidative decarboxylation of the COOH-terminal cysteine residue of the epidermin precursor peptide EpiA to a (Z)-enethiol structure (see Fig. 7) (13,17,20,21). The unsaturated thioether bridge is formed by addition of the enethiol group to a didehydroalanine residue, produced by dehydration of Ser at position ϩ19 of EpiA (residues within the COOHterminal propeptides of lantibiotic precursor peptides are labeled with "ϩ"). Recently, molecular characterization of EpiD helped to identify homologous enzymes catalyzing the decarboxylati...

Phaeobacter gallaeciensis genomes from globally opposite locations reveal high similarity of adaptation to surface life

“…Thus, we postulate that homocysteine acts as a source of sulfur atoms for TDA. In support of this, the essential tdaF gene most probably encodes a homo-oligomeric flavin-containing cysteine decarboxylase, which catalyzes the oxidative decarboxylation of cysteine residues for several substrates (Majer et al, 2002). Therefore, TdaF could provide a reactive, sulfur-containing precursor for the final steps of TDA synthesis (Figure 6).…”

Production of a Class II Two-Component Lantibiotic of Streptococcus pneumoniae Using the Class I Nisin Synthetic Machinery and Leader Sequence

“…The gene encoding this type of enzyme is also found in the gene clusters of epidermin and mersacidin. The modifications made by the flavoproteins are required for full activity of these peptides (24,29). Whereas NisT displays rather broad transport specificity of peptides fused to the leader peptide of nisin, NisP has been shown to process only fully modified prenisin (19).…”

“…A FAD-dependent flavoprotein catalyzes this reaction for mersacidin, a lantibiotic produced by Bacillus sp. (29). Another flavoprotein, which is flavin mononucleotide (FMN) dependent, catalyzes the same reaction for epidermin, a lantibiotic of S. epidermidis, and this enzyme is essential for formation of a biologically activity peptide (24).…”

4′-Phosphopantetheine Biosynthesis in Archaea

“…Although several active site residues of eubacterial and eukaryotic CoaC activities are not conserved in Methanocaldococcus Dfp (12), we were able to demonstrate its PPC decarboxylase activity. Furthermore, it is shown that HisCoaC (and thus Dfp) forms homododecamers like the E. coli Dfp protein and the related peptidyl-cysteine decarboxylases EpiD and MrsD (7,10,13). We show that M. jannaschii CoaB is a CTP-dependent enzyme, although the nucleotide binding motif II contains a Lys residue, which is characteristic for the ATP-dependent PPC synthetases (5).…”