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.

Highly potent antimicrobial peptide derivatives of bovine cateslytin

“…A similar potentiation was observed with a tryptophan and arginine containing 15 residue lactoferricin derivatives, where a substitution for tryptophan in position 8 resulted in a 6-fold increase in antibacterial activity against E. coli. 29 An additional modification, in which the serine residues were replaced with threonine, resulted in the most potent peptide (7) in this series. Overall, the amphiphilic balance of cateslytin was gradually shifted to an increased hydrophobicity by the modifications.…”

Metabolic Fate of Lactoferricin-Based Antimicrobial Peptides: Effect of Truncation and Incorporation of Amino Acid Analogs on the In Vitro Metabolic Stability

“…It is noteworthy that reduction of the disulfide generates a linear peptide with similar activities that allowed the development of shorter synthetic derivatives with maintained properties (Bellamy et al, 1992). Much of the work was initially focused on the 11-and 15-residue fragments LfcinB 4-14 and LfcinB 1-15 , yielding important insights into the structural requirements (Kang et al, 1996;Strøm et al, 2000Strøm et al, , 2002Nguyen et al, 2005). Through these studies, it was shown that a combination of basicity and hydrophobicity, mainly in the form of arginine and tryptophan, is necessary for activity (Haug and Svendsen, 2001;Strøm et al, 2002Strøm et al, , 2003.…”

Human Lactoferricin Is Partially Folded in Aqueous Solution and Is Better Stabilized in a Membrane Mimetic Solvent

“…As a result, further study was given to the isolation of the lactoferricin peptide produced in vivo by digestion of bovine lactoferrin (27,40). More recently, additional work has focused upon the identification of key antimicrobial segments and enhancement of the activity of the various shorter synthetic human lactoferricin (LfcinH) peptide analogs by using amino acid substitutions and various activity assays (7,10,11,28,30,37,42,47). These studies have established not only that LfcinH has antimicrobial, antiviral, and antifungal activities but also that it is capable of stimulating the immune system and neutralizing endotoxin.…”