Disruption of Saccharomyces cerevisiae by Plantaricin 149 and investigation of its mechanism of action with biomembrane model systems

Abstract

The action of a synthetic antimicrobial peptide analog of Plantaricin 149 (Pln149a) against Saccharomyces 24 ^ cerevisiae and its interaction with biomembrane model systems were investigated. Pln149a was shown to 25 inhibit S. cerevisiae growth by more than 80% in YPD medium, causing morphological changes in the yeast 26 wall and remaining active and resistant to the yeast proteases even after 24 h of incubation. Different 27 membrane model systems and carbohydrates were employed to better describe the Pln149a interaction with 28 cellular components using circular dichroism and fluorescence spectroscopies, adsorption kinetics and 29 surface elasticity in Langmuir monolayers. These assays showed that Pln149a does not interact with either 30 mono/polysaccharides or zwitterionic LUVs, but is strongly adsorbed to and incorporated into negatively 31 charged surfaces, causing a conformational change in its secondary structure from random-coil to helix upon 32 adsorption. From the concurrent analysis of Pln149a adsorption kinetics and dilatational surface elasticity 33 data, we determined that 2.5 μM is the critical concentration at which Pln149a will disrupt a negative DPPG 34 monolayer. Furthermore, Pln149a exhibited a carpet-like mechanism of action, in which the peptide initially 35 binds to the membrane, covering its surface and acquiring a helical structure that remains associated to the 36 negatively charged phospholipids. After this electrostatic interaction, another peptide region causes a strain 37 in the membrane, promoting its disruption.