Characterizing Toxin-Membrane Interactions and Lasso Peptide Folding with Enhanced Free Energy Sampling

John Nguyen, Graduate Research Assistant
Seminar
DSL Seminar

Molecular dynamics (MD) simulations provide atomistic insight into biological processes but are often limited by poor sampling of rare events and long-timescale transitions. Enhanced sampling methods overcome these limitations by enabling efficient exploration of complex free-energy landscapes. In this talk, I will present enhanced sampling studies of toxin–membrane interactions and the folding of lasso peptides. For mycolactone, a cytotoxic macrolide responsible for Buruli ulcer, simulations with mammalian plasma and endoplasmic reticulum (ER) membrane models reveal a probabilistic preference for the ER, driven by membrane hydration, deformation, and lipid-specific interactions. Isomer-specific simulations further show that cytotoxic mycolactone B stabilizes a closed Sec61 translocon conformation, inhibiting protein translocation. I will also discuss enhanced sampling approaches to characterize lasso peptide folding, identifying reaction coordinates that distinguish pre-lasso from nonthreaded states and demonstrating how sequence optimization and chemical modification can significantly stabilize the pre-lasso ensemble.