Bacteria produce a wide range of antimicrobial peptides to protect themselves from competing microbes. One of such compounds is epidermin, a member of the lantibiotic family, produced and secreted by Staphylococcus species. Lantibiotics are synthesized as precursors and then modified by other proteins. Antimicrobial peptides such as epidermin exhibit highly potent biological activities, ranging from antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA) to anticancer activity against mouse leukemia cells.
The maturation of epidermin requires a series of modification reactions. EpiD protein catalyzes the first step of epidermin modifications which is the decarboxylation of the C-terminal cysteine residue and producing a reactive (Z)-enethiol intermediate. The reaction requires flavin mononucleotide (FMN) which is reduced to FMNH2. The protein belongs to a family of flavoproteins called as HFCD proteins (homo-oligomeric flavin- containing Cys-decarboxylases). The biologial assembly of EpiD is a dodecamer forming a sphere with 4 trimers placed at the vertices of a tetrahedron. EpiD is essential for epidermin biosynthesis.