title: Antibacterial activity of 15-residue lactoferricin derivatives.
abstract: Lactoferricins are a class of antibacterial peptides isolated after gastric-pepsin digest of the mammalian iron-chelating-protein lactoferrin. For investigation of antibacterial activity, we prepared short synthetic derivatives of bovine, human, caprine, murine and porcine lactoferricins with 15-amino-acid residues of high sequence homology. The peptides corresponded to amino-acid residues 17-31 of the mature bovine lactoferrin. Only the bovine and caprine derivatives displayed measurable antibacterial activity, with the bovine one having a minimal inhibitory concentration of 24 microM and being 10 times more active than the caprine one against Escherichia coli. An alanine-scan of the bovine lactoferricin derivative was performed to identify specific amino acids that were important for the antibacterial activity. We found that neither of the two tryptophan residues (Trp 6 and Trp 8) present in the bovine lactoferricin derivative could be replaced by alanine without a major loss of antibacterial activity. The other lactoferricin derivatives tested contained only one tryptophan residue (Trp 6). Modified human, caprine and porcine lactoferricin derivatives containing two tryptophan residues (Trp 6 and Trp 8) displayed minimal inhibitory concentrations of 74, 174 and 219 microM, respectively, which represented up to a six-fold increase in antibacterial activity. The alanine-scan also revealed that the antibacterial activity was increased when acetamidomethyl-protected cysteine and unprotected glutamine (Cys 3 and Gln 7) were replaced with alanine. Only the bovine lactoferricin derivative and a few of its alanine-modified derivatives displayed measurable activity against Staphylococcus aureus.
authors.affiliation: Department of Chemistry, Faculty of Science, University of Tromsø, Norway.
authors.forename: M B
authors.initials: MB
authors.lastname: Strøm
authors.forename: O
authors.initials: O
authors.lastname: Rekdal
authors.forename: J S
authors.initials: JS
authors.lastname: Svendsen
mesh_terms: D000409:Alanine / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D002942:Circular Dichroism; D004926:Escherichia coli / Q000187:drug effects; D006801:Humans; D007781:Lactoferrin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D013211:Staphylococcus aureus / Q000187:drug effects; D014364:Tryptophan / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D010446:Peptide Fragments; D014364:Tryptophan; D007781:Lactoferrin; D000409:Alanine