Magainin 1 is an antimicrobial peptide discovered in the skin of Xenopus laevis.

Magainin 1 kill bacteria by permeabilizing the cell membranes without exhibiting significant toxicity against mammalian cells. The main target of the peptide is considered to be the lipid matrix of the membranes[1]. Magainin 1 and 2 have a similar amino-acid sequence. Magainin 2 has higher antimicrobial activity than magainin 1[2]. Magainin 1 interacts with acidic lipids through electrostatic interactions followed by hydrophobic interactions to form an amphiphilic helix, inducing the leakage. Magainin 1 induces the leakage of calcein specifically out of negatively-charged vesicles. The peptide binds to bovine brain phosphatidylserine sonicated vesicles according to the Langmuir isotherm with a binding constant of 3.8×105 M-1 and a binding-site number of 0.10 per lipid molecule[3]. Magainin 2 displays antibiotic activity against numerous Gram-negative and Gram-positive bacteria. A similar spectrum of activity is seen on assay of magainin 1[4].

[1]. Matsuzaki K, et al. Magainins as paradigm for the mode of action of pore forming polypeptides. Biochim Biophys Acta. 1998 Nov 10;1376(3):391-400. [2]. Watanabe H, et al. Channel Current Analysis for Pore-forming Properties of an Antimicrobial Peptide, Magainin 1, Using the Droplet Contact Method. Anal Sci. 2016;32(1):57-60. [3]. Matsuzaki K, et al. Magainin 1-induced leakage of entrapped calcein out of negatively-charged lipid vesicles. Biochim Biophys Acta. 1989 May 19;981(1):130-4. [4]. Zasloff M, et al. Magainins, a class of antimicrobial peptides from Xenopus skin: isolation, characterization of two active forms, and partial cDNA sequence of a precursor. Proc Natl Acad Sci U S A. 1987 Aug;84(15):5449-53.