Why is the microtubule lattice helical?

Area of Science:

• Biophysics
• Cell Biology
• Structural Biology

Background:

• Microtubules are essential cellular structures formed by tubulin heterodimers.
• The helical lattice of microtubules exhibits a consistent left-handed chirality, the reason for which remains unexplained.
• Understanding microtubule structure is crucial for cell division and intracellular transport.

Purpose of the Study:

• To investigate the functional necessity of left-handed chirality in microtubule polymerization.
• To explore the physical and dynamical implications of microtubule helicity.
• To determine if chirality is essential for the mechanical properties or assembly process of microtubules.

Main Methods:

• Computational simulations were employed to model microtubules lacking inherent helicity ('counterfactual biology').
• The mechanical properties of helical and non-helical simulated microtubules were compared.
• The 'blind mason' problem was used as a conceptual framework to analyze assembly dynamics.

Main Results:

• Simulated microtubules without helicity exhibited comparable mechanical properties to naturally occurring helical microtubules.
• The study suggests that helicity is not essential for the fundamental mechanical stability of microtubules.
• Helical chirality was found to provide a solution to the 'blind mason' problem in microtubule assembly.

Conclusions:

• The left-handed chirality of microtubules is likely driven by a dynamical, rather than a purely structural or mechanical, requirement.
• Helicity facilitates the self-assembly process of microtubules, ensuring correct structure formation from tubulin subunits.
• Further research is needed to fully elucidate the dynamical role of chirality in microtubule polymerization and cellular function.