Synthesis of bicyclic alkene-/alkane-bridged nisin mimics by ring-closing metathesis and their biochemical evaluation as lipid II binders: toward the design of potential novel antibiotics

Chembiochem. 2007 Sep 3;8(13):1540-54. doi: 10.1002/cbic.200700244.

Abstract

This report describes the design, synthesis, and biochemical evaluation of alkene- and alkane-bridged AB(C)-ring mimics of the lantibiotic nisin. Nisin belongs to a class of natural antimicrobial peptides, and has a unique mode of action: its AB(C)-ring system binds to the pyrophosphate moiety of lipid II. This mode of action was the rationale for the design of smaller nisin-derived peptides to obtain novel potential antibiotics. As a conformational constraint the thioether bridge was mimicked by an alkene- or alkane isostere. The peptides of the linear individual ring precursors were synthesized on solid support or in solution, and cyclized by ring-closing metathesis in solution with overall yields of between 36 and 89 %. The individual alkene-bridged macrocycles were assembled in solution by using carbodiimide-based synthesis protocols for the corresponding AB(C)-ring mimics. These compounds were tested for their binding affinity toward lipid II by evaluation of their potency to inhibit nisin-induced carboxyfluorescein release from large unilamellar vesicles. It was found that these AB(C)-ring mimics were not able to induce membrane leakage; however, they acted by inhibiting nisin-induced carboxyfluorescein release; this indicates their affinity toward lipid II. These results imply that an alkene or alkane moiety is a suitable thioether bridge mimic.

MeSH terms

  • Alkanes / chemical synthesis
  • Alkanes / chemistry*
  • Alkenes / chemical synthesis
  • Alkenes / chemistry*
  • Anti-Bacterial Agents / chemical synthesis*
  • Anti-Bacterial Agents / chemistry
  • Anti-Bacterial Agents / metabolism
  • Catalysis
  • Chromatography, High Pressure Liquid
  • Chromatography, Thin Layer
  • Computers, Molecular
  • Cyclization
  • Drug Design*
  • Fluoresceins / chemistry
  • Fluoresceins / metabolism
  • Models, Molecular
  • Molecular Mimicry*
  • Nisin / chemical synthesis*
  • Nisin / chemistry
  • Nisin / metabolism
  • Peptide Fragments / chemical synthesis
  • Peptide Fragments / chemistry
  • Peptide Fragments / metabolism*
  • Phosphatidylcholines / metabolism
  • Polyisoprenyl Phosphate Oligosaccharides
  • Stereoisomerism
  • Unilamellar Liposomes / chemistry
  • Unilamellar Liposomes / metabolism
  • Uridine Diphosphate N-Acetylmuramic Acid / analogs & derivatives*
  • Uridine Diphosphate N-Acetylmuramic Acid / metabolism

Substances

  • Alkanes
  • Alkenes
  • Anti-Bacterial Agents
  • Fluoresceins
  • Peptide Fragments
  • Phosphatidylcholines
  • Polyisoprenyl Phosphate Oligosaccharides
  • Unilamellar Liposomes
  • Uridine Diphosphate N-Acetylmuramic Acid
  • muramyl-NAc-(pentapeptide)pyrophosphoryl-undecaprenol
  • Nisin
  • 6-carboxyfluorescein
  • 1,2-oleoylphosphatidylcholine