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Applied and Environmental Microbiology, January 2007, p. 415-420, Vol. 73, No. 2
0099-2240/07/$08.00+0     doi:10.1128/AEM.01293-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Molecular View by Fourier Transform Infrared Spectroscopy of the Relationship between Lactocin 705 and Membranes: Speculations on Antimicrobial Mechanism

Centro de Referencia para Lactobacilos (CERELA/CONICET), Chacabuco 145 Tucumán, Argentina,¹ Departamento de Bioquímica de la Nutrición, Instituto Superior de Investigaciones Biológicas (INSIBIO) and Instituto de Química Biológica Dr. Bernabé Bloj (CONICET-UNT), Chacabuco 461 (4000) Tucumán, Argentina,² Unidad de Biofisica (CSIC-UPV) and Departamento de Bioquímica y Biología Molecular, Bilbao, España³

Received 6 June 2006/ Accepted 9 October 2006

Lactocin 705 is a bacteriocin whose activity depends upon the complementation of two peptides, termed Lac705 and Lac705ß. Neither Lac705 nor Lac705ß 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 (Lac705 and Lac705ß) with dipalmitoylphosphatidylcholine liposomal membranes. Both peptides show the ability to interact with the zwitterionic membrane but at different bilayer levels. While Lac705 interacts with the interfacial region inducing dehydration, Lac705ß peptide interacts with only the hydrophobic core. This paper presents the first experimental evidence that supports the hypothesis that Lac705 and Lac705ß peptides could form a transmembrane oligomer. From the obtained results, a mechanism of action of lactocin 705 on membrane systems is proposed. The component Lac705 could induce the dehydration of the bilayer interfacial region, and the Lac705ß peptide could insert in the hydrophobic region of the membrane where the peptide has adequate conditions to achieve the oligomerization.

Published ahead of print on 27 October 2006.