Kinesin's cover-neck bundle folds forward to generate force

Area of Science:

• Molecular biology
• Biophysics
• Cellular mechanics

Background:

• Kinesin motors are crucial for intracellular transport, but the precise mechanism of force generation remains unclear.
• Previous models focused on the neck linker and nucleotide-binding pocket for energy transduction.
• Recent simulations proposed a role for the N-terminal cover strand in forming a 'cover-neck bundle' for forward movement.

Purpose of the Study:

• To investigate the role of the N-terminal cover strand in kinesin's force generation mechanism.
• To experimentally validate the proposed cover-neck bundle model for kinesin stepping.

Main Methods:

• Utilized optical trapping to measure the motility of kinesin motor proteins.
• Compared the performance of wild-type kinesin with cover strand mutants.
• Performed kinetic analyses to assess force-generating capacity and load dependence.

Main Results:

• Kinesin mutants with altered or deleted cover strands showed significantly impaired force generation and increased load dependence.
• A complete deletion of the cover strand resulted in minimal motor function.
• An assisting load partially rescued motility in the cover strand deletion mutant, suggesting an alternative to the power stroke.

Conclusions:

• The N-terminal cover strand is essential for kinesin's force-generating stepping mechanism through dynamic cover-neck bundle formation.
• This finding challenges previous models by identifying a novel force-generating element.
• Targeting the cover strand offers a potential strategy for engineering kinesin motors with modified mechanical properties.