Interaction with lipid II induces conformational changes in bovicin HC5 structure.
Bovicin HC5 is a lantibiotic produced by Streptococcus bovis HC5 that targets the cell wall precursor lipid II. An understanding of the modes of action against target bacteria can help broadening the clinical applicability of lantibiotics in human and veterinary medicine. In this study, the interaction of bovicin HC5 with lipid II was examined using tryptophan fluorescence and circular dichroism spectroscopy with model membrane systems that do or do not allow pore formation by bovicin HC5. In the presence of lipid II, a blue-shift of 12 nm could be observed for the fluorescence emission maximum of the tryptophan residue for all of the membrane systems tested. This change in fluorescence emission was paralleled by a decrease in accessibility toward acrylamide and phospholipids carrying a spin-label at the acyl chain; the tryptophan residue of bovicin HC5 was located near the twelfth position of the membrane phospholipid acyl chains. Moreover, the binding of lipid II by bovicin HC5 induced remarkable conformational changes in the bovicin HC5 structure. The interaction of bovicin HC5 with lipid II was highly stable even at pH 2.0. These results indicate that bovicin HC5 interacts directly with lipid II and that the topology of this interaction changes under different conditions, which is relevant for the biological activity of the peptide. To our knowledge, bovicin HC5 is the only bacteriocin described thus far that is able to interact with its target in extreme pH values, and this fact might be related to its unique structure and stability.
Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
Aline Dias
AD
Paiva
Nicole
N
Irving
Eefjan
E
Breukink
Hilário Cuquetto
HC
Mantovani
D020106:Acrylamide; D000595:Amino Acid Sequence; D001430:Bacteriocins / Q000737:chemistry* / Q000302:isolation & purification; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D055550:Protein Stability; D013050:Spectrometry, Fluorescence; D016985:Streptococcus bovis / Q000737:chemistry*; D014364:Tryptophan; D014538:Uridine Diphosphate N-Acetylmuramic Acid / Q000031:analogs & derivatives* / Q000737:chemistry
D001430:Bacteriocins; D008567:Membranes, Artificial; D014538:Uridine Diphosphate N-Acetylmuramic Acid; C514465:bovicin HC5, Streptococcus bovis HC5; C069249:muramyl-NAc-(pentapeptide)pyrophosphoryl-undecaprenol; D020106:Acrylamide; D014364:Tryptophan