SEMINÁRIO DO GRUPO DE BIOFÍSICA - FGE
“The antimicrobial peptide K0-W6-Hya1 induces stable structurally modified lipid domains in anionic membranes”
Profa. Dra. Maria Teresa Lamy, IFUSP
Dia: 19 de abril, quarta-feira, às 13h.
Local: Sala 201 – Ala 1, IFUSP
Abstract:
Considering the known different mode of action of antimicrobial peptides in neutral and anionic cell membranes, the present work compares the action of the antimicrobial peptide K0-W6-Hya1 (Lys-IlePhe-Gly-Ala-Ile-Trp-Pro-Leu-Ala-Leu-Gly-Ala-Leu-Lys-Asn-Leu-Ile-Lys-NH2) with neutral and negatively charged model membranes, namely, liposomes composed of DPPC (dipalmitoyl phosphatidyl choline) and DPPG (dipalmitoyl phosphatidyl glycerol), and a mixture of the two lipids. Differential Scanning Calorimetry (DSC), steady state fluorescence of the Trp residue, Dynamic Light Scattering (DLS) and the measurement of the leakage of an entrapped fluorescent dye were performed with large unilamellar vesicles (LUVs). All techniques evidenced the different action of the peptide in neutral and anionic vesicles. Trp fluorescence spectroscopy shows that the differences are related not only to the partition of the cationic peptide in neutral and anionic membranes, but also to the different penetration of the peptide into the lipid bilayers: Trp goes deeper into DPPG than into DPPC. DSC shows that the peptide is strongly attached to anionic bilayers, giving rise to the coexistence of two different lipid regions, one depleted of peptide and another peptidedisturbed, possibly a stable or transient polar pore. This contrasts with the average effect produced by the peptide in DPPC membranes, probably related to peptide-membrane diffusion. Moreover, in mixed bilayers (DPPC:DPPG), the peptide sequesters negatively charged lipids, creating peptide-rich anionic lipid regions, strongly disturbing the membrane. The distinct structural interactions displayed by the peptide in DPPC and DPPG membranes could be related to the different mechanisms of action of the peptide in anionic prokaryotic and neutral eukaryotic cell membranes.
