Single fungal kinesin motor molecules move processively along microtubules

Area of Science:

• Molecular Biology
• Biophysics
• Cell Biology

Background:

• Kinesins are molecular motors that transport cargo along microtubules, powered by ATP hydrolysis.
• Processivity, the ability of a motor to take many steps before detaching, is crucial for efficient transport.
• While dimeric kinesins are typically processive, structural elements like the neck domain can influence this behavior.

Purpose of the Study:

• To quantify and compare the processivity of Neurospora kinesin (NKin), a phylogenetically distant dimeric kinesin.
• To investigate the role of NKin's unusual neck domain in its motor activity.
• To compare NKin's processivity to that of human kinesin (HKin) under identical experimental conditions.

Main Methods:

• Gliding assays to observe microtubule translocation by single NKin molecules.
• Fluorescence-based assays to track the movement and detachment of single, labeled NKin and HKin motors.
• Quantitative analysis of translocation distances and motor detachment events.

Main Results:

• Neurospora kinesin (NKin) demonstrates significant processivity, moving an average of 2.14 micrometers in gliding assays.
• Single-molecule tracking revealed NKin motors travel an average of 1.75 micrometers before detaching from microtubules.
• NKin exhibits at least twice the processivity of human kinesin (HKin), which moved an average of 0.83 micrometers under identical conditions.

Conclusions:

• Neurospora kinesin (NKin) is a highly processive molecular motor, exceeding the processivity of human kinesin (HKin).
• The findings suggest that NKin's unique structural features, particularly its neck domain, contribute to its enhanced processivity.
• This study provides a foundation for further research into the molecular mechanisms underlying kinesin-based processive motility.