magainin-2-peptide--xenopus and mastoparan

This study investigated the ability of anaerobic periodontal bacteria to inactivate and resist killing by antimicrobial peptides through production of extracellular proteases. Antibacterial activities of peptides were assessed in a double-layer agarose diffusion assay, and MICs and MBCs were determined in broth microdilution assays. Culture supernates of Porphyromonas gingivalis and Prevotella spp. inactivated mastoparan, magainin II and cecropin B whilst Gram-positive oral supragingival bacteria had no effect. Inactivation was prevented by protease inhibitors and was unaffected by 45% human serum. Purified proteases from the periodontopathogen Porph. gingivalis inactivated peptides [cecropin B, brevinin, CAMEL (cecropin A 1-7 + melittin 2-9), mastoparan] as would be predicted from the amino acid sequences of the peptides and the known bond specificities of these Arg-x and Lys-x enzymes. MALDI-TOF MS revealed that inactivation of cecropin B by Porph. gingivalis protease was due to specific cleavage of the molecule. Inactivation of cecropin B by proteases took 10-15 min. Paradoxically, MICs of cecropin B against Porph. gingivalis and Prevotella intermedia were low, while Prevotella nigrescens was resistant, suggesting that production of proteases alone is insufficient to protect Porph. gingivalis and Prev. intermedia from the action of antimicrobial peptides. Thus, antimicrobial peptides could be developed as therapeutic agents targeted against specific periodontal pathogens.

Topics: Amino Acid Sequence; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Endopeptidases; Insect Proteins; Intercellular Signaling Peptides and Proteins; Magainins; Microbial Sensitivity Tests; Molecular Sequence Data; Peptides; Porphyromonas gingivalis; Prevotella; Prevotella intermedia; Wasp Venoms; Xenopus Proteins

The effect of the alpha-helical polycationic peptides magainin 2, melittin, mastoparan and cecropin on the viability of Brucella abortus 544 (type species), B. abortus S19 (vaccine strain) and B. abortus S2308 (vaccine challenge strain) was determined. Rough mutants of these strains and the rough candidate vaccine strain B. abortus RB51 were also tested. S. typhimurium was used as a control. The peptides did not affect the viability of B. abortus smooth strains but some of the peptides affected viability of the rough strains. Magainin 2 at a concentration of 100 micrograms ml-1 did not reduce the viability of the rough B. abortus strains. Cecropin at a concentration of 15 micrograms ml-1 reduced the viability of the rough strains by approximately 10-fold. Mastoparan at a concentration of 50 micrograms ml-1 reduced the viability of the rough strains by approximately 100-fold. Melittin at a concentration of 20 micrograms ml-1 reduced the viability of the rough strains of B. abortus by approximately 1000-fold. The brucellae were significantly more resistant to all the cationic peptides than was S. typhimurium.

Topics: Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Brucella abortus; Intercellular Signaling Peptides and Proteins; Magainins; Melitten; Microbial Sensitivity Tests; Peptides; Wasp Venoms; Xenopus Proteins