Abstract
Magainin 2 and PGLa are antimicrobial peptides found together in frog skin secretions. When added as a mixture they show an order of magnitude increase in antibacterial activity and in model membrane permeation assays. Here we demonstrate that both peptides can form fibers with beta-sheet/turn signature in ATR-FTIR- and CD-spectroscopic analyses, but with different morphologies in EM images. Whereas, fiber formation results in acute reduction of the antimicrobial activity of the individual peptides, the synergistic enhancement of activity remains for the equimolar mixture of PGLa and magainin 2 also after fibril formation. The biological significance and potential applications of such supramolecular aggregates are discussed.
Highlights
Magainin 2 and PGLa were among the first cationic amphipathic peptides for which the biological regulation and antimicrobial activity was explored in greater depth (Zasloff, 1987; Gibson, 1991)
We have found that both peptides can form large supramolecular assemblies including fibers under physiological conditions and that this association has a strong effect on their antimicrobial activity
The antimicrobial activities of magainin 2a and PGLa have been suggested to be associated with their cationic and amphiphilic character that allows them to partition into the interface of bacterial membranes (Bechinger, 1999; Zasloff, 2002)
Summary
Magainin 2 and PGLa were among the first cationic amphipathic peptides for which the biological regulation and antimicrobial activity was explored in greater depth (Zasloff, 1987; Gibson, 1991). In nature these peptides are both produced by and stored together in the granular glands of the South African clawed frog Xenopus laevis (Giovannini et al, 1987) and from each frog up to tens of milligrams of highly concentrated gel-like vesicular skin secretions have been isolated upon stimulation of release (Kiss and Michl, 1962; Gibson et al, 1986; Giovannini et al, 1987). The molecular mechanisms for synergistic membrane disruption and antibacterial activities
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