Mean-field study of the role of lateral cracks in microtubule dynamics

Area of Science:

• Biophysics
• Cell Biology
• Computational Biology

Background:

• Microtubules (MTs) are crucial cytoskeletal polymers.
• Understanding MT dynamics at the molecular level is essential for cell function.
• Previous theoretical models lacked explicit representation of key structural features and kinetics.

Purpose of the Study:

• To develop a novel 2D mean-field model (MFM) for microtubule dynamics.
• To bridge the gap between dimer-scale processes and macroscale MT behavior.
• To analytically predict and quantify critical MT dynamic features.

Main Methods:

• Developed a novel 2D mean-field model (MFM) incorporating dimer-level kinetics.
• Explicitly represented inter-protofilament cracks and both longitudinal/lateral dimer interactions.
• Compared MFM predictions with numerical simulations of a computational dimer-scale model.

Main Results:

• The MFM analytically predicts a minimal soluble tubulin concentration for polymerization.
• Identified steady-state growth and shortening phases with quantifiable velocities.
• Described an unstable pause state near zero velocity.
• Estimated the size of the GTP cap in growing MTs.
• MFM predictions showed good agreement with numerical simulations.

Conclusions:

• The 2D MFM provides a robust analytical framework for microtubule dynamics.
• The model successfully links molecular interactions to emergent macroscopic properties of MTs.
• This work offers quantitative insights into polymerization, depolymerization, and cap dynamics.