cecropin-b-protein--insecta 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