Magainin 2

Magainin 2 (Magainin II) is an?antimicrobial?peptide (AMP) isolated from the skin of the African clawed frog Xenopus laevis. Magainin 2 displays antibiotic activity against numerous gram-negative and gram-positive bacteria. Magainin 2 also is active against protozoa^[1]. Magainin 2 exerts its cytotoxicity effects by preferential interactions with anionic phospholipids abundant in bacterial membranes^[2]. In Vitro: Magainin 2 exhibits bactericidal effects and induces morphological changes in Escherichia coli regarding early apoptosis. Magainin 2 induces the expression of a bacterial protein with affinity for the caspase substrate and effects the expression of RecA as a caspase-like protein^[1]. Magainin 2 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. Application of 10 μg /mL magainin 2 to Paramecium caudatum, a protozoan, in pond water caused an osmotic swelling of the cell and a subsequent cell burst, suggesting that the peptide could perturb membrane functions responsible for osmotic balance^[2]. Magainin 2 permeabilizes bacterial and mammalian membranes in significantly different ways. The peptide forms pores with a diameter of about 2.8 nm (less than 6.6 nm) in B. megaterium, and translocates into the cytosol. In contrast, the peptide significantly perturbes the membrane of CHO-K1 cells, permitting the entry of a large molecule (larger than 23 nm) into the cytosol, accompanied by membrane budding and lipid flip-flop, mainly accumulating in mitochondria and nuclei^[3].