A synthetic peptide has been developed that "may lead to the creation of a new class of antimicrobial agents", according to Dr Emilie Porter and colleagues (University of Wisconsin, Madison, US).
They describe magainins in Nature (2000;404:565) as a naturally occurring class of medium-sized peptides used by organisms as a defence against microbial infection.
Magainin molecules contain an a helix. They are attracted to bacterial membranes, where the helix disrupts the bacterial membrane by an unknown mechanism. However, they are rapidly degraded in living tissue and can be toxic to human cells as well as to those of bacteria.
The researchers developed a synthetic b-chain magainin derivative that mimicked the natural molecules. They found that the antimicrobial activity of the b-magainin derivative matched that of naturally occurring magainin. In addition, the synthetic molecule was effective against a vancomycin-resistant strain of Enterococcus faecalis and a methicillin-resistant Staphylococcus aureus.
The authors say that because similar peptides are haemolytic, which would not be desirable in an antimicrobial, they tested the effect of the b-derivative on human blood cells. They found that it was only weakly haemolytic.
The b-chain magainins are promising antimicrobials, say the authors, because they mimic the natural defensive activity displayed by natural peptides, the b-peptide "backbone" is resistant to degradation by proteases and a choice of structures is possible.