Analysis of microtubule rigidity using hydrodynamic flow and thermal fluctuations

Area of Science:

• Biophysics
• Cell Biology
• Structural Biology

Background:

• Microtubules are essential cytoskeletal polymers involved in cell structure, division, and transport.
• Understanding the mechanical properties of microtubules, such as flexural rigidity, is crucial for elucidating their biological functions.
• Existing methods for measuring microtubule mechanics have limitations.

Purpose of the Study:

• To develop and validate two novel, independent methods for accurately measuring the flexural rigidity of microtubules.
• To investigate how ligand binding affects microtubule mechanical properties.
• To correlate mechanical properties with microtubule structure and biological function.

Main Methods:

• Developed a hydrodynamic flow method to analyze microtubule bending at equilibrium.
• Developed a thermal fluctuation method to measure rigidity from free end movements.
• Grew microtubules from axonemal pieces adhered to a coverslip for both methods.

Main Results:

• Standard GDP microtubules exhibit a flexural rigidity of 0.85 x 10^-23 Nm^2 and a persistence length of 2 mm.
• Phosphate analogs (AlF4-, [BeF3-, H2O]) increased flexural rigidity and persistence length approximately 3-fold.
• Microtubule-stabilizing drugs Taxol and Taxotere decreased flexural rigidity and altered microtubule superstructure.

Conclusions:

• The developed methods provide reliable measurements of microtubule flexural rigidity.
• Microtubule mechanical properties are sensitive to biochemical modifications and drug interactions.
• Changes in flexural rigidity and superstructure likely influence microtubule's role in cellular processes.