Snf7 spirals sense and alter membrane curvature

Area of Science:

• Cell Biology
• Biophysics
• Structural Biology

Background:

• The Endosomal Sorting Complex Required for Transport III (ESCRT-III) system mediates membrane scission.
• Understanding how planar ESCRT-III assemblies transition to 3D structures is crucial but poorly understood.

Purpose of the Study:

• To investigate the structural dynamics and membrane interaction of Snf7, a key ESCRT-III component, under non-planar conditions.
• To elucidate the mechanisms by which ESCRT-III proteins induce membrane topological transitions.

Main Methods:

• Utilized high-speed atomic force microscopy (HS-AFM) on non-planar, non-crowded, and non-rigid lipid bilayers.
• Observed Snf7 monomer and spiral assembly behavior in response to varying membrane geometries and support properties.

Main Results:

• Snf7 monomers showed curvature insensitivity, while Snf7-spirals adapted conformation to membrane geometry.
• Snf7-spirals remodeled to minimize stress in uncrowded conditions and compacted/buckled on non-rigid supports.
• Observed deformation of underlying bilayers by Snf7-spirals.

Conclusions:

• Snf7 protein structure is sufficient to mediate topological membrane transitions.
• Findings support the loaded spiral spring model for ESCRT-III function in membrane scission.