lactoferrin and tritrpticin

Drug-resistant microorganisms ('superbugs') present a serious challenge to the success of antimicrobial treatments. Subsequently, there is a crucial need for novel bio-control agents. Many antimicrobial peptides (AMPs) show a broad-spectrum activity against bacteria, fungi or viruses and are strong candidates to complement or substitute current antimicrobial agents. Some AMPs are also effective against protozoa or cancer cells. The tryptophan (Trp)-rich peptides (TRPs) are a subset of AMPs that display potent antimicrobial activity, credited to the unique biochemical properties of tryptophan that allow it to insert into biological membranes. Further, many Trp-rich AMPs cross bacterial membranes without compromising their integrity and act intracellularly, suggesting interactions with nucleic acids and enzymes. In this work, we overview some archetypal TRPs derived from natural sources, i.e., indolicidin, tritrpticin and lactoferricin, summarising their biochemical properties, structures, antimicrobial activities, mechanistic studies and potential applications.

Topics: Animals; Anti-Infective Agents; Antimicrobial Cationic Peptides; Drug Resistance, Microbial; Humans; Lactoferrin; Models, Molecular; Oligopeptides; Tryptophan

Staphylokinase (Sak) is a plasminogen activator protein that is secreted by many Staphylococcus aureus strains. Sak also offers protection by binding and inhibiting specific antimicrobial peptides (AMPs). Here, we evaluate Sak as a more general interaction partner for AMPs. Studies with melittin, mCRAMP, tritrpticin and bovine lactoferricin indicate that the truncation of the first ten residues of Sak (SakΔN10), which occurs in vivo and uncovers important residues in a bulge region, improves its affinity for AMPs. Melittin and mCRAMP have a lower affinity for SakΔN10, and in docking studies, they bind to the N-terminal segment and bulge region of SakΔN10. By comparison, lactoferricin and tritrpticin form moderately high affinity 1:1 complexes with SakΔN10 and their cationic residues form several electrostatic interactions with the protein's α-helix. Overall, our work identifies two distinct AMP binding surfaces on SakΔN10 whose occupation would lead to either inhibition or promotion of its plasminogen activating properties.

Topics: Animals; Antimicrobial Cationic Peptides; Binding Sites; Cathelicidins; Cattle; Lactoferrin; Melitten; Metalloendopeptidases; Models, Molecular; Molecular Docking Simulation; Oligopeptides; Plasminogen; Protein Structure, Secondary; Staphylococcus aureus; Substrate Specificity

We evaluated the effect of tritrpticin, lactoferrin, killer decapeptide and scrambled peptide in vitro against Naegleria fowleri trophozoites compared with amphotericin B. Tritrpticin (100 microg/ml) caused apoptosis of N. fowleri trophozoites (2x10(5) cells/ml), while lactoferrin, killer decapeptide and scrambled peptide did not. On Gormori trichrome staining, tritrpticin affected the elasticity of the surface membrane and reduced the size of the nuclei of N. fowleri trophozoites. The ultrastructure surface membrane and food cup formation of the trophozoites were 100% inhibited. These results are consistent with inhibition of the nfa1, Mp2CL5 of the treated trophozoite, which plays a role in food cup formation. Tritrpticin 100 microg/ml was not toxic against SK-N-MC cells. Our findings suggest tritrpticin has activity against the surface membrane and nfa1 and Mp2CL5 of N. fowleri trophozoites and could be developed as a potential therapeutic agent.

Topics: Animals; Anti-Infective Agents; Antibodies, Protozoan; Apoptosis; Cell Membrane; Coculture Techniques; Electrophoresis, Polyacrylamide Gel; Humans; Killer Factors, Yeast; Lactoferrin; Membrane Proteins; Microscopy, Electron, Scanning; Naegleria fowleri; Neuroblastoma; Oligopeptides; Peptide Fragments; Polymerase Chain Reaction; Protozoan Proteins; Staining and Labeling; Trophozoites

Synthetic peptides derived from human and bovine lactoferricin, as well as tritrpticin sequences, were assayed for antimicrobial activity against wild-type Escherichia coli and LPS mutant strains. Antimicrobial activity was only obtained with peptides derived from the bovine lactoferricin sequence and peptides corresponding to chimeras of human and bovine sequences. None of the peptides corresponding to different regions of native human lactoferricin showed any antimicrobial activity. The results underline the importance of the content of tryptophan and arginine residues, and the relative location of these residues for antimicrobial activity. Results obtained for the same assays performed with LPS mutants suggest that lipid A is not the main binding site for lactoferricin which interacts first with the negative charges present in the inner core. Computer modelling of the most active peptides led to a model in which positively charged residues of the cationic peptide interact with negative charges carried by the LPS to disorganise the structure of the outer membrane and facilitate the approach of tryptophan residues to the lipid A in order to promote hydrophobic interactions.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Binding Sites; Carbohydrate Metabolism; Carbohydrate Sequence; Escherichia coli; Hydrophobic and Hydrophilic Interactions; Lactoferrin; Lipopolysaccharides; Molecular Sequence Data; Mutation; Oligopeptides; Phospholipids

The interaction of several tryptophan (Trp)-rich cationic antimicrobial peptides with membranes was investigated. These peptides included tritrpticin, indolicidin, lactoferricin B (Lfcin B), and a shorter fragment of lactoferricin (LfcinB4-9). The average environment of the Trp residues of these peptides was assessed from their fluorescence properties, both the wavelength of maximal emission as well as the red edge effect. The insertion of the peptides into vesicles of differing composition was examined using quenching of the Trp fluorescence, with both soluble acrylamide and nitroxide-labelled phospholipids as well as by chemical modification of the Trp residues with N-bromosuccinimide. The results were consistent with the Trp side chains positioned mostly near the membrane-water interface. The extent of burial of the Trp side chains appears to be greater in vesicles containing phospholipids with the anionic phosphatidylglycerol headgroup. Leakage of the aqueous contents of liposomes was also measured using the 8-aminonaphthalene-1,3,6-trisulfonic acid--p-xylene-bis-pyridinium bromide assay. Tritrpticin, which demonstrated the greatest red edge shift, also displayed the largest amount of leakage from liposomes. Taken together, the results illustrate that cationic Trp-rich antimicrobial peptides preferentially disrupt large unilamellar vesicles with a net negative charge following their insertion into the interfacial region of the phospholipid bilayer.

Topics: Anti-Infective Agents; Antimicrobial Cationic Peptides; Circular Dichroism; Kinetics; Lactoferrin; Lipid Bilayers; Liposomes; Membrane Lipids; Oligopeptides; Pyridinium Compounds; Spectrometry, Fluorescence; Tryptophan