RSC School Seminar - Dr Evelyne Deplazes (University of Queensland)

Title: An integrative approach to characterise membrane-altering peptides

Abstract:

Pore-forming and membrane-altering peptides and proteins have evolved independently several times to perform a range of biological functions. Examples include antimicrobial peptides, bacterial toxins and viroporins. Many of these peptides self-assembles into oligomeric,  membrane-embedded pores. Due to their small size, dynamic nature and the presence of a membrane, these pores are challenging to characterise using structural biology approaches.

In this seminar, I will use two selected projects to illustrate how we combine MD simulations, tethered lipid bilayer membranes (tBLM/EIS) in conjunction with electrical impedance spectroscopy (EIS) and other biophysical chemistry experiments to characterise the structure, ion and lipid selectivity of oligomeric pores and other membrane-altering peptides.

The first project focuses on GALA, a pH-responsive, pore-forming peptide designed to facilitate endosomal drug release. We demonstrate that tBLM/EIS experiments can provide both ion selectivity and estimates on pore size. This information can be used to validate pores with different oligomeric sizes predicted from MD simulations1. For the second project, I present data from a project aimed at elucidating the synergy mechanism between the antifungal drug amphotericin B and Lactofungin, a peptide derived from Lactoferrin2 . Our recent shows that the synergy between Lactofungin and AMB is lipid-dependent and ergosterol-specific without the peptide directly interacting with the membrane.

1. Deplazes, E.; Hartmann, L. M.; Cranfield, C. G.; Garcia, A., Structural Characterization of a Cation-Selective, Self-Assembled Peptide Pore in Planar Phospholipid Bilayers. The Journal of Physical Chemistry Letters 2020, 11 (19), 8152-8156.
2. Fernandes, K. E.; Payne, R. J.; Carter, D. A., Lactoferrin-Derived Peptide Lactofungin Is Potently Synergistic with Amphotericin B. Antimicrobial Agents and Chemotherapy 2020, 64 (10), e00842-20.