Initial binding sites of antimicrobial peptides in Staphylococcus aureus and Escherichia coli.

We examined the initial binding sites of magainin 1, cecropin P1 and lactoferricin B in Staphylococcus aureus and Escherichia coli. All 3 peptides were active against E. coli, whereas only lactoferricin B exerted any activity against S. aureus. Soluble lipoteichoic acid and lipopolysaccharide both interacted with all 3 peptides, whereas soluble teichoic acid interacted with lactoferricin B only. Antibodies against teichoic acid diminished the activity of lactoferricin B, while antibodies against lipoteichoic acid had no influence on the activity of lactoferricin B. Antibodies against lipopolysaccharide diminished the activity of lactoferricin B and magainin 1, but had no effect on the activity of cecropin P1 against E. coli. We conclude that the initial binding sites of lactoferricin B in S. aureus, and of lactoferricin B and magainin 1 in E. coli, are teichoic acid and lipopolysaccharide, respectively. Cecropin P1 seems to interact with a different binding site than those of magainin 1 and lactoferricin B in E. coli.