Effect of Anionic Antimicrobial Peptides on model lipid membranes.

NOE, M. M; RODRIGUEZ JA; BARREDO VACCHELLI GR; CAMPERI SA; PERILLO, M A; NOLAN MV

Córdoba

Congreso; LI Reunión Anual de la Sociedad Argentina de Biofísica,; 2023

Sociedad Argentina de Biofísica,

Anionic antimicrobial peptides (AAP) were first reported in the early 1980s. They have been established as part of the innate immune systems of vertebrates, invertebrates and plants, and they are active against bacteria, fungi, viruses and pests such as insects. Membrane interaction appears key to the antimicrobial function of AAMPs. In the present work we use the anionic peptide β-lg125-135 that is obtained from tryptic hydrolysate of β-lactoglobulin and evaluate its interaction with model membranes. We use DPPC or DPPC:DPPG mixtures as a model of eukaryotic or bacterial membrane, respectively. I previous works we showed that β-lg125-135 interacts preferentially with anionic monolayers. In the present work we evaluate the effect o β-lg125-135 on membrane order and permeability. Unilamelar vesicles were used as model membranes. DPH and TMA-DPH fluorescence anisotropy was used to evaluate the effect of peptide interaction on membrane order: DPH probe sense the hydrocarbon region whereas the fluorescent probe TMA-DPH, with an additional charged group, is anchored at the lipid/water interface and reports on a bilayer region that is distinct from that of the hydrophobic DPH, which senses a deeper region. Results obtained show that for vesicles composed of the equimolar mixture of lipids, the anisotropy of both probes tested increases in the presence of peptide. For dpPC vesicles this effect was not so noticeable at the temperatures tested. These would indicate that the peptide partitions into the lipid mixing bilayers, increasing the molecular order. The effect of peptide-membrane interaction on vesicles permeability was evaluated as the release of the carboxyfluorescein trapped in liposomes. We measured the increase in carboxyfluorescein fluorescence intensity at increasing AAP concentrations to elucidate the relationship between bilayer disruption and lipid bilayer perturbation. Results obtained showed that the higher the peptide-lipid molar ratio, the higher the percentage of release of the fluorescent probe.