title: Influence of specific amino acid side-chains on the antimicrobial activity and structure of bovine lactoferrampin.
abstract: Lactoferrin is an 80 kDa iron binding protein found in the secretory fluids of mammals and it plays a major role in host defence. An antimicrobial peptide, lactoferrampin, was identified through sequence analysis of bovine lactoferrin and its antimicrobial activity against a wide range of bacteria and yeast species is well documented. In the present work, the contribution of specific amino acid residues of lactoferrampin was examined to evaluate the role that they play in membrane binding and bilayer disruption. The structures of all the bovine lactoferrampin derivatives were examined with circular dichroism and nuclear magnetic resonance spectroscopy, and their interactions with phospholipids were evaluated with differential scanning calorimetry and isothermal titration calorimetry techniques. From our results it is apparent that the amphipathic N-terminal helix anchors the peptide to membranes with Trp 268 and Phe 278 playing important roles in determining the strength of the interaction and for inducing peptide folding. In addition, the N-terminal helix capping residues (DLI) increase the affinity for negatively charged vesicles and they mediate the depth of membrane insertion. Finally, the unique flexibility in the cationic C-terminal region of bovine lactoferrampin does not appear to be essential for the antimicrobial activity of the peptide.
authors.affiliation: University of Calgary, Department of Biological Sciences, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.
authors.forename: Evan F
authors.initials: EF
authors.lastname: Haney
authors.forename: Kamran
authors.initials: K
authors.lastname: Nazmi
authors.forename: Jan G M
authors.initials: JG
authors.lastname: Bolscher
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Vogel
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology; D002152:Calorimetry, Differential Scanning; D002417:Cattle; D004912:Erythrocytes / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects; D006461:Hemolysis; D006801:Humans; D007781:Lactoferrin / Q000737:chemistry* / Q000494:pharmacology; D008823:Micelles; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000494:pharmacology; D010715:Phosphatidylglycerols / Q000737:chemistry; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013298:Streptococcus sanguis / Q000187:drug effects; D013816:Thermodynamics; D053835:Unilamellar Liposomes / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D008823:Micelles; D010446:Peptide Fragments; D010715:Phosphatidylglycerols; D053835:Unilamellar Liposomes; C502040:lactoferrampin; D015060:1,2-Dipalmitoylphosphatidylcholine; D012967:Sodium Dodecyl Sulfate; D007781:Lactoferrin; C030345:1,2-dipalmitoylphosphatidylglycerol