Biophysical Society Conference | Tahoe 2024

Molecular Biophysics of Membranes

Poster Abstracts

21-POS Board 6 HIGH PRESSURE BIOPHYSICS FOR DISSECTING ROLES OF NON-BILAYER LIPIDS IN BIOLOGICAL MEMBRANES Daniel Milshteyn 1 ; Jacob R Winnikoff 2 ; Itay Budin 1 ; 1 University of California, San Diego, Chemistry and Biochemistry, La Jolla, CA, USA 2 Harvard University, Organismic and Evolutionary Biology, Cambridge, MA, USA While lamellar bilayers are the basis of cell membranes, many abundant biological lipids form nonlamellar structures, like the inverse hexagonal (H ii ) phase, that could facilitate high membrane curvature and fusion/fission processes in cells. To better understand the regulation of global membrane curvature and cellular access to nonlamellar phases, we have employed the use of hydrostatic pressure incubations of model microorganisms as an assay to challenge and test biophysical roles of non-bilayer lipids. Hydrostatic pressure compresses the acyl chains of conical lipids, like phosphatidylethanolamine (PE), into cylindrical geometries with less negative curvature resembling that of phosphatidylcholine (PC). To assess the roles of non-bilayer lipid abundance in preserving membrane dynamics under pressure, we screened the fitness of yeast strains engineered with varied PE/PC ratios under high pressure incubation. Polar lipid extracts of these strains were then analyzed by high pressure small angle x-ray scattering (HP-SAXS) to evaluate accessibility of lamellar to H ii phases. In parallel, we have tested the dependence of membrane fusion on negatively-curved lipids with synthetic vesicles featuring varied PE/PC ratios using a FRET-based high pressure stopped-flow assay. In combination, these methodologies allowed us to investigate the role of PE, and other non-bilayer lipids, in preserving access to nonlamellar topologies and membrane dynamics under biophysically constrained conditions. We demonstrate the applicability of high pressure experimental biology to uncover subtle roles of lipids and biochemical pathways involved in fundamental membrane biophysics that may be difficult to detect in ambient environments.

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