A molecular view by FTIR spectroscopy of the relationship between lactocin 705 and membranes: speculations on antimicrobial mechanism

CASTELLANO PATRICIA; VIGNOLO GRACIELA,; FARIAS RICARDO NORBERTO,; ARRONDO JOSE LUIS; CHEHIN ROSANA

APPLIED AND ENVIRONMENTAL MICROBIOLOGY

American Society for Microbiology

Año: 2007 vol. 73 p. 415 - 420

0099-2240

Lactocin 705 is a bacteriocin whose activity depends upon the complementation of two peptides, termed Lac705a and Lac705b. Neither Lac705a nor Lac705b displayed bacteriocin activity by itself when the growth of sensitive cells was monitored. To obtain molecular insights into the lactocin 705 mechanism of action, Fourier transform infrared spectroscopy was used to investigate the interactions of each peptide (Lac705a and Lac705b) with dipalmitoylphosphatidylcholine liposomal membranes. Both peptides show ability to interact with zwitterionic membrane but at different bilayer levels. While Lac705á interacts with the interfacial region inducing dehydration, Lac705b peptide interacts only with the hydrophobic core. This paper presents the first experimental evidence that supports the hypothesis that Lac705a and Lac705b peptides could form a transmembrane oligomer. From the obtained results a bactericidal mechanism of lactocin 705 on sensitive cells is proposed. In the first place, the component Lac705á could induce dehydration of the bilayer interfacial region helping Lac705â peptide insertion in the hydrophobic region of the membrane where the peptide has adequate conditions to achieve the oligomerization.