Pseudin-2: An antimicrobial peptide with low hemolytic activity from the skin of the paradoxical frog

Four structurally related peptides (pseudins 1-4) with antimicrobial activi ty were isolated from an extract of the skin of the paradoxical frog Pseudi s paradoxa (Pseudidae). Pseudin-2 (GLNALKKVFQGIHEA-IKLINNHVQ) was the most abundant peptide (22 nmol/g tissue) and also the most potent (minimum inhib itory concentrations, MIC = 2.5 muM against Escherichia coli, 80 muM agains t Staphylococcus aureus, and 130 muM against Candida albicans). The concent ration of pseudin-2 producing 50% hemolysis of human erythrocytes was > 300 muM. Circular dichroism studies showed that the pseudins belong to the cla ss of cationic, amphipathic alpha -helical antimicrobial peptides but their amino acid sequences are not similar to any previously characterized pepti des from frog skin. The pseudins do, however, show sequence similarity with a region at the C-terminus of DEFT, a death effector domain-containing pro tein expressed in mammalian testicular germ cells that is involved in the r egulation of apoptosis. (C) 2001 Academic Press.