Human lactoferrin contains a 46 residue sequence named lactoferricin H thought to be responsible for its antimicrobial properties. Synthetic peptides HLTI, correspomling to the loop region of human lactoferricin (FQWQR-NMRKVRGPPVS) and HLT2, corresponding to its charged portion (FQWQRNMRKVR), exerted significant antibacterial effects against £. co//serotype O111 strains NCTC 8007 and ML35. The corresponding sequences In native human lactoferrin were shown to adopt a charged helix and hydrophoble tall within the N-lobe remote from the iron binding site. Sequence similarities between lactoferricin and dermaseptin and magainins suggest that laetoferricin may act as an amphipathie alpha helix.