A fluorescence spectroscopy study of the microcin J25 peptide and model membranes interaction

FERNANDO DUPUY, ROBERTO MORERO

Rosario, Santa Fe, Argentina

Congreso; XXXV Reunión Anual de la Sociedad Argentina de Biofísica; 2006

Sociedad Argentina de Biofisica

Microcin J25 is a 21 aminoacid peptide active against Escherichia coli and Salmonella enteritidis strains. The antimicrobial peptide shows a distinctive lasso-structure with high hydrophobic character without tryptophan in the molecule (1).  It has been shown that RNA polymerase activity is inhibited by the peptide, both “in vitro” and “in vivo” assays (2); however, there are certain sensitive strains whose RNA polymerase activity is not inhibited. The peptide activity against cellular and model membranes has also been shown. Respiratory chain enzymes from bacteria (3) and rat heart mitochondria are inhibited by MccJ25 (4). Moreover, the peptide penetrate into phospholipids monolayer (5) and the fluidity degree of liposomes is increased. In this communication we used fluorescence spectroscopy techniques to study the MccJ25 interaction with small unilamellar vesicles prepared with various phospholipid compositions.  Several mutant peptides containing a single tryptophan along the primary structure were obtained and purified. Each of the following amino acids namely Ile13, Thr15 and Val6 were replaced by tryptophan. The antibiotic activity was conserved in each molecule. The affinity and selectivity of the peptide-membrane interaction was studied with the fluorescence emission of the tryptophan. Solvent exposed peptides when interacting with membranes were assesed by quenching effiency of water soluble quenchers; and the position of the peptides within the membranes were determined by using quenchers bound to fatty acid. Our results indicates that the interaction MccJ25 and its derivatives with model membranes made of specific composition is of high selectivity and low affinity, it is not depending of membrane’s fluidity degree and the peptide locates next to phospholipids interfacial region. Ref1.        Rosengren KJ, Clark RJ, Daly NL, Goransson U, Jones A, Craik DJ. J Am Chem Soc. 2003 Oct 15;125(41):12464-74.2.        Delgado, M. A., Rintoul, M. R., Farias, R. N., and Salomon, R. A. J.Bacteriol. (2001) 183, 4543-45503.        Rintoul, M. R., de Arcuri, B. F., Salomon, R. A., Farias, R. N., and Morero, R. D. FEMS Microbiology Letters (2001) 204, 265-2704.        Niklison Chirou MV, Minahk CJ, Morero RD. Biochem Biophys Res Commun (2004) 317:882-886.5.        Bellomio A, Oliveira R, Maggio B, Morero R, J. of Colloid and Interface Science (2005) 285, 118–124