Dynein arms are oscillating force generators

Area of Science:

• Biophysics
• Cell Biology
• Molecular Motors

Background:

• Eukaryotic flagella generate rhythmic motion crucial for cellular functions.
• Dynein motor proteins are responsible for powering flagellar beating.
• The intrinsic properties of dynein and the axoneme's role in oscillation are not fully understood.

Purpose of the Study:

• To investigate whether oscillation is an intrinsic property of dynein arms.
• To determine if an intact axoneme is required for dynein-driven oscillation.
• To characterize the force generation and oscillatory behavior of individual or small groups of dynein arms.

Main Methods:

• Utilized optical trapping nanometry to measure forces generated by dynein arms.
• Isolated doublet microtubules were used as tracks for dynein motor activity.
• Activated dynein arms using photolysis of caged ATP to initiate force generation measurements.

Main Results:

• A few dynein arms generated a peak force of ~6 pN, moving microtubules processively.
• Observed oscillatory force and displacement with peak-to-peak force of ~2 pN and amplitude of ~30 nm.
• Oscillation frequency (~70 Hz at 0.75 mM ATP) was dependent on ATP concentration and observed even with inner dynein arms alone.

Conclusions:

• Dynein arms exhibit intrinsic oscillatory force generation, potentially independent of the full axoneme structure.
• The data suggest that dynein arm oscillation is a fundamental mechanism underlying flagellar beating.
• This finding provides insights into the basic mechanics of molecular motors driving biological movement.