Polymer-like Model to Study the Dynamics of Dynamin Filaments on Deformable Membrane Tubes

Area of Science:

• Biophysics
• Cell Biology
• Structural Biology

Background:

• Peripheral membrane proteins modulate membrane shape and curvature.
• Dynamin, a mechanochemical GTPase, forms helical filaments that constrict and scission membrane tubes.
• The GTP-independent membrane remodeling role of dynamin's structure is not fully understood.

Purpose of the Study:

• To develop a dynamical polymer-chain model for helical elastic filaments bound to deformable membrane tubes.
• To investigate the role of dynamin's intrinsic shape and elasticity in membrane remodeling.
• To determine the equilibrium shapes and mechanical properties of dynamin-membrane interactions.

Main Methods:

• Development of a dynamical polymer-chain model incorporating thermal fluctuations and lipid flow.
• Molecular dynamics simulations of dynamin's tetrameric building block to obtain elastic parameters.
• Coarse-grained structure-based simulations of a 17-dimer dynamin filament.
• Analysis of equilibrium shapes and sensitivity to membrane tension and stiffness.

Main Results:

• Dynamin filament stiffness is comparable to membrane stiffness.
• Filament pitch, not radius, is sensitive to membrane tension and stiffness.
• Model predictions for inner tube radius closely match experimental estimates.
• Dynamin's stalk region is implicated in GTP-independent membrane shaping.

Conclusions:

• Dynamin's intrinsic elasticity and helical structure are key to its membrane constriction ability.
• The developed model provides a framework for understanding dynamin-mediated membrane remodeling.
• Further mesoscopic modeling can incorporate dynamin's motor function for a complete picture.