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Citation (#276):

Antibacterial activity of 15-residue lactoferricin derivatives

Authors: Strøm, M.B., Svendsen, J.S., Rekdal, O.

Journal: The Journal of Peptide Research 2000, 56(5).

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 µm 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 µm, 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.

Keywords: alanine-scan; Antibacterial peptide; Lactoferricin; minimal inhibitory concentration; peptide modifications

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