Turbidimetric studies on microtubule sliding using the stopped-flow-light-scattering method

Area of Science:

• Biophysics
• Cell Biology
• Biochemistry

Background:

• The active sliding of microtubules within axonemes is crucial for flagellar motility.
• Understanding the precise velocity of this sliding is key to deciphering the mechanics of ciliary and flagellar movement.

Purpose of the Study:

• To investigate the utility of stopped-flow light-scattering turbidimetry for quantifying microtubule sliding velocity.
• To establish a correlation between turbidimetry measurements and established methods for determining microtubule sliding speed.

Main Methods:

• Utilized demembranated sea-urchin sperm flagellar axonemes.
• Employed a high time-resolution stopped-flow light-scattering assay to measure turbidity changes during ATP-induced disintegration.
• Analyzed the time course of turbidity using single exponential function to determine the rate of disintegration (R).
• Compared R with microtubule sliding velocity (V) obtained via cinematomicrography.

Main Results:

• A strong correlation (r = 0.9973) was found between the rate of disintegration (R) measured by turbidimetry and the microtubule sliding velocity (V).
• The relationship was defined as R = 0.22 x V.
• The temperature dependence (Q10) of the sliding velocity was estimated to be 2.0-2.3 within a MgATP concentration range of 43-820 microM.

Conclusions:

• Light-scattering turbidimetry is a validated and effective method for measuring microtubule sliding velocity in axonemes.
• This technique offers a high-resolution approach to study the kinetics of microtubule-based motor proteins.
• The findings provide insights into the thermal properties of flagellar motor function.