Carboxyl Analogue of Mutacin 1140, a Scaffold for Lead Antibacterial Discovery

Abstract

Mutacin 1140 belongs to the epidermin group of lantibiotics. Epidermin class lantibiotics are ribosomally synthesized and posttranslationally modified antibiotics with potent activity against Gram-positive bacteria. In particular, this class is effective at targeting drug-resistant Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus (MRSA), Mycobacterium tuberculosis, and Clostridium difficile.residue is derived from a decarboxylation of a terminal cysteine that is involved in lanthionine ring formation. Studies on mutacin 1140 have revealed new insight into the structural importance of the C-terminal AviCys residue. A C-terminal carboxyl analogue of mutacin 1140 was engineered. Capping the C-terminal carboxyl group with a primary amine restores bioactivity and affords a novel opportunity to synthesize new analogues. A C-terminal fluorescein-labeled mutacin 1140 analogue traps lipid II into a large lipid II lantibiotic complex, similar to that observed in vivo for the lantibiotic nisin. A C-terminal carboxyl analogue of mutacin 1140 competitively inhibits the activity of native mutacin 1140 and nisin. The presence of a C-terminal carboxyl group prevents the formation of the large lipid II lantibiotic complexes but does not prevent the binding of the lantibiotic to lipid II. IMPORTANCE This study addressed the importance of the C-terminal S-[(Z)-2-aminovinyl]-D-cysteine (AviCys) residue for antibacterial activity. We have learned that the posttranslational modification for making the AviCys residue is presumably important for the lateral assembly mechanism of activity that traps lipid II into a large complex. The C-terminal carboxyl analogue of this class of lantibiotics is agreeable to the addition of a wide variety of substrates. The addition of fluorescein enabled in vivo visualization of the epidermin class of lantibiotics in action. These results are significant because, as we demonstrate, the presence of the AviCys residue is not essential for bioactivity, but, more importantly, the removal of the carboxyl group is essential. The ability to make a C-terminal carboxyl analogue that is modifiable will facilitate the synthesis of novel analogues of the epidermin class of lantibiotics that can be developed for new applications.KEYWORDS lantibiotic, decarboxylation, mutacin 1140, nisin L antibiotics, or lanthionine-containing antibiotics, are characterized by their posttranslational modifications (PTMs) (1). Dehydrations of serine and threonine residues into dehydroalanine and dehydrobutyrine residues, respectively, are a common modification found in lantibiotics. These dehydrated residues can be cyclized with cysteines to form thioether bridges, which are called lanthionines (2, 3). The unmodified lantibiotic is encoded by the gene lanA. The genes for biosynthesis and regulation are generally grouped together in a biosynthetic gene cluster. In class I lantibiotics, dehydrations are carried out by the dehydratase, LanB. Lanthionine ring formation is catalyzed by LanC. Lantibiotics can ...

Complete synthesis of the bicyclic ring of a mutacin analog with orthogonally protected lanthionine via solid‐phase intracyclization

“…Prior to the synthesis of bicyclic C/D ring, the AviCys was modified at position 22 to a cysteamine because it was previously shown that the AviCys functional group may not be essential for optimal antimicrobial activity (Figure B) . This modification simplifies the synthetic strategy and allows to confirm whether or not an cysteamine can indeed replace an AviCys and confirms the impact of this substitution on biological activity.…”

“…Prior to the synthesis of bicyclic C/D ring, the AviCys was modified at position 22 to a cysteamine because it was previously shown that the AviCys functional group may not be essential for optimal antimicrobial activity ( Figure 1B). 43 This modification simplifies the synthetic The building block lanthionine 7 precursor was synthesized as previously reported, [10][11][12] which was then followed by esterification to yield lanthionine OPfp ester 7. Compound 7 was used as presented in Scheme 2.…”

“…While a MU1140‐COOH analog (Figure B, R=COOH) presented with a reduced antimicrobial activity (by a factor of 256‐fold, as compared with MU1140), a MU1140‐NHMe analog (Figure B, R=CONHMe) maintained its activity. Other alkyl amide derivatives of MU1140 present a 2‐32 fold reduction in antimicrobial activity, as compared with MU1140 …”

“…While a MU1140. 43 The current report is the first that describes the synthesis of orthogonally protected lanthionine analog cysteamine via aziridine ring opening. We also present the chemical synthesis of the bicyclic C/D ring of a MU1140 analog ( Figure 1C) using SPPS that may be useful to complete the synthesis of MU1140 analogs of therapeutic value.…”

Covalent Structure and Bioactivity of the Type AII Lantibiotic Salivaricin A2

“…Lipid II binding assay. A lipid II binding assay using a thin-layer chromatography (TLC) procedure was performed as previously described (48). Briefly, the mobile solvent used consisted of butanol-acetic acid-water-pyridine in a 15:3:12:10 volume ratio.…”