PMID:9596699

Citation	Chapple, DS, Mason, DJ, Joannou, CL, Odell, EW, Gant, V and Evans, RW (1998) Structure-function relationship of antibacterial synthetic peptides homologous to a helical surface region on human lactoferrin against Escherichia coli serotype O111. Infect. Immun. 66:2434-40
Abstract	Lactoferricin includes an 11-amino-acid amphipathic alpha-helical region which is exhibited on the outer surface of the amino-terminal lobe of lactoferrin. Synthetic peptides homologous to this region exhibited potent antibacterial activity against a selected range of both gram-negative and gram-positive bacteria. An analog synthesized with methionine substituted for proline at position 26, which is predicted to disrupt the helical region, abolished antibacterial activity against Escherichia coli and considerably reduced antibacterial activity against Staphylococcus aureus and an Acinetobacter strain. The mode of action of human lactoferrin peptide (HLP) 2 against E. coli serotype O111 (NCTC 8007) was established by using flow cytometry, surface plasmon resonance, and transmission electron microscopy. Flow cytometry was used to monitor membrane potential, membrane integrity, and metabolic processes by using the fluorescent probes bis-1,3-(dibutylbarbituric acid)-trimethine oxonol, propidium iodide, and carbonyl cyanide m-chlorophenylhydrazone, respectively. HLP 2 was found to act at the cell membrane, causing complete loss of membrane potential after 10 min and of membrane integrity within 30 min, with irreversible damage to the cell as shown by rapid loss of viability. The number of particles, measured by light scatter on the flow cytometer, dropped significantly, showing that bacterial lysis resulted. The peptide was shown to bind to E. coli O111 lipopolysaccharide by using surface plasmon resonance. Transmission electron microscopy revealed bacterial distortion, with the outer membrane becoming detached from the inner cytoplasmic membrane. We conclude that HLP 2 causes membrane disruption of the outer membrane, resulting in lysis, and that structural considerations are important for antibacterial activity.
Links	PubMed PMC108221
Keywords	Amino Acid Sequence; Anti-Bacterial Agents/chemical synthesis; Anti-Bacterial Agents/pharmacology; Bacteriolysis; Cell Membrane Permeability; Escherichia coli/classification; Escherichia coli/drug effects; Escherichia coli/immunology; Escherichia coli/ultrastructure; Humans; Lactoferrin/pharmacology; Membrane Potentials/drug effects; Molecular Sequence Data; O Antigens; Peptide Fragments/chemical synthesis; Peptide Fragments/pharmacology; Peptides/chemical synthesis; Peptides/pharmacology; Protein Binding; Protein Structure, Secondary; Sequence Homology, Amino Acid; Structure-Activity Relationship
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
HUMAN:TRFL	involved_in	GO:0045087: innate immune response	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
HUMAN:TRFL	enables	GO:0001530: lipopolysaccharide binding	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete
HUMAN:TRFL	involved_in	GO:0045837: negative regulation of membrane potential	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
HUMAN:TRFL	involved_in	GO:0051673: membrane disruption in other organism	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
HUMAN:TRFL	involved_in	GO:0050830: defense response to Gram-positive bacterium	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
HUMAN:TRFL	involved_in	GO:0050829: defense response to Gram-negative bacterium	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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