Differential antibacterial activities of bLF derived peptides

CHANETON L; PÉREZ SÁEZ JM; BUSSMANN LE

Potrero de los Funes. San Luis, Argentina

Congreso; XXIV Reunión Anual de la Sociedad de Biología de Cuyo; 2006

SBCuyo

Bovine mastitis is the most prevalent and costly disease in dairy farm. Bovine milk lactoferrin (bLF) is an iron-binding glycoprotein that seems to play an important role in non-specific response against mastitis infections due to its bacteriostatic and bactericidal activities. Treatment of bLF with proteases is reported to yield a hydrolysate which, while unable to bind iron, remains active against gram negative and gram positive bacteria. In this work, we performed pepsin bLF digestions at acidic pH. Peptides were subsequently separated by size using differential dialysis, resulting in two fractions: one larger than 12kDa and the other smaller. Our results show that antibacterial activity against S. aureus is restricted to low molecular mass peptides, whereas E. coli growth inhibition seems to depend on high molecular mass peptides. In order to further characterize these peptides, we performed analytical cationic exchange chromatography at pH 7.0. Most of the short peptide fraction was unable to interact with cationic resins, indicating its neutral or basic nature. In contrast, the large peptide fraction showed a more extensive interaction with this resin, demonstrating its cationic composition. Our results show that different bLF derived peptides exhibit differential activities against E. coli and S. aureus. Since these peptide fractions also appear to have dissimilar biochemical properties, it seems feasible that two different mechanisms are responsible for biological activities of bLF peptides against gram (–) and gram (+) bacteria.