Inflence on the cell membrane of Trichosporon beigelii by fungicidal peptide derived from cecropin A(1-8)-magainin 2(1-12)

Abstract

The fungicidal activities of the cecropin A(1-8)-magainin 2(1-12) (CA- MA) and its analogues with amino acid substitution were measured by a growth inhibition assay using Trichosporon beigelii. CA-MA displayed potent fungicidal activity (minimal inhibitory concentration: 5 μg/ml) against Trichosporon beigelii with no hemolytic activity. Substitution (A12-CA-MA: analogue 2) of Ala to Lys at position 12 of CA-MA caused an increase in fungicidal activity without any increase in hemolytic activity. In order to investigate the fungicidal mechanism of analogue 2, it was reacted with Trichosporon beigelii protoplasts. The morphological changes and the failure of the cell wall regeneration of the protoplast by analogue 2 were observed. Moreover, the amounts of released potassium ion by the peptide were increased. These results suggested that the fungicidal mechanism of analogue 2 may be due to the pore formation or the detergent-like disruption of cell membranes.