Potassium Efflux Induced by a New Lactoferrin-Derived Peptide Mimicking the Effect of Native Human Lactoferrin on the Bacterial Cytoplasmic Membrane

摘要

A 31-amino acid synthetic peptide (NH_2-FFSASCVPGADKGQFPNLCRLCAGTGENKCA-COOH) was chemically synthesized based on the amino acid sequence of a region of human lactoferrin homologous to other sequences present in the N-and C-lobes of all members of the transferrin family proteins. The peptide, termed kaliocin-1, and lactoferrin showed a bactericidal effec in assays performed in low-ionic-strength conditions. This is the first time that it is shown that the antimicrobial effec of lactoferrin depends on the extracellular cation concentration. The antimicrobial effect of kaliocin-1 was lower than that of human lactoferrin, but their acivities were inhibited by Na~+ or K~+ in a cation concentration-dependent manner. In addition, the peptide was able to mimic native lactoferrin, inducng K~+-efflux and a selecive dissipation of the transmembrane electrical potential of Escherichia coli cells withot causing extensive damage of the outer and inner bacterial membranes. In contrast, the peptide, but not lactoferrin, was able to permeabilize different ions through liposomal membranes. The hypothetical interaction of kaliocin-1 with a bacterial membrane compound is discussed based in the different ion flux induced on cellular and artificial membranes as well as data from circular dichroism assays. Kaliocin-1 was not cytotoxic and could be a suitable model for the design of analogs able to mimic the antibacterial effect of human lactoferrin.