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The lantibiotic mersacidin inhibits peptidoglycan synthesis by targeting lipid II
H Brötz1, G Bierbaum, K Leopold
1Institut für Medizinische Mikrobiologie und Immunologie, Universität Bonn, Germany.
Abstract:
The lantibiotic mersacidin exerts its bactericidal action by inhibition of peptidoglycan biosynthesis. It interferes with the membrane-associated transglycosylation reaction; during this step the ultimate monomeric peptidoglycan precursor, undecaprenyl-pyrophosphoryl-MurNAc-(pentapeptide)-GlcNAc (lipid II) is converted into polymeric nascent peptidoglycan. In the present study we demonstrate that the molecular basis of this inhibition is the interaction of mersacidin with lipid II. The adsorption of [14C]mersacidin to growing cells, as well as to isolated membranes capable of in vitro peptidoglycan synthesis, was strictly dependent on the availability of lipid II, and antibiotic inhibitors of lipid II formation strongly interfered with this binding. Direct evidence for the interaction was provided by studies with isolated lipid II. [14C]mersacidin associated tightly with [14C]lipid II micelles; the complex was stable even in the presence of 1% sodium dodecyl sulfate. Furthermore, the addition of isolated lipid II to the culture broth efficiently antagonized the bactericidal activity of mersacidin. In contrast to the glycopeptide antibiotics, complex formation does not involve the C-terminal D-alanyl-D-alanine moiety of the lipid intermediate. Thus, the interaction of mersacidin with lipid II apparently occurs via a binding site which is not targeted by any antibiotic currently in use.
Insights
Mersacidin, a lantibiotic antibiotic, kills bacteria by inhibiting peptidoglycan biosynthesis. This study reveals mersacidin directly binds to lipid II, a key molecule in this process, offering a novel antibiotic target.
Area of Science:
- Microbiology
- Biochemistry
- Drug Discovery
Background:
- Lantibiotics are a class of peptide antibiotics with antimicrobial activity.
- Mersacidin inhibits bacterial cell wall synthesis, specifically peptidoglycan biosynthesis.
- The precise molecular target of mersacidin's inhibition has been under investigation.
Purpose of the Study:
- To elucidate the molecular mechanism by which mersacidin inhibits peptidoglycan biosynthesis.
- To identify the direct interaction target of mersacidin within the bacterial cell.
- To explore potential novel antibiotic targets based on mersacidin's mechanism.
Main Methods:
- Radiolabeling of mersacidin ([14C]mersacidin) and lipid II ([14C]lipid II) for binding studies.
- Assessing mersacidin adsorption to bacterial cells and isolated membranes.
- Investigating the effect of lipid II availability and inhibitors on mersacidin binding.
- Characterizing the stability of the mersacidin-lipid II complex using sodium dodecyl sulfate (SDS).
- Evaluating the antagonistic effect of isolated lipid II on mersacidin's bactericidal activity.
Main Results:
- Mersacidin adsorption to cells and membranes is dependent on the availability of lipid II.
- Inhibitors of lipid II formation reduce mersacidin binding, suggesting lipid II as the binding site.
- Direct binding of [14C]mersacidin to [14C]lipid II micelles was confirmed, forming a stable complex.
- Exogenous lipid II antagonized the bactericidal effect of mersacidin.
- Mersacidin's interaction with lipid II does not involve the D-alanyl-D-alanine moiety, unlike glycopeptide antibiotics.
Conclusions:
- Mersacidin exerts its bactericidal effect by directly interacting with lipid II, a crucial precursor in peptidoglycan synthesis.
- This interaction targets a binding site on lipid II distinct from those targeted by existing antibiotics.
- The mersacidin-lipid II interaction represents a promising novel target for the development of new antibacterial agents.