KIF1A alternately uses two loops to bind microtubules

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Kinesin is a motor protein that transports cargo within cells along microtubule tracks.
• The mechanism by which kinesin converts adenosine triphosphate (ATP) hydrolysis into mechanical force remains incompletely understood.

Purpose of the Study:

• To elucidate the structural basis of kinesin's mechanical movement during ATP hydrolysis.
• To investigate the role of specific kinesin loops in microtubule interaction and detachment.

Main Methods:

• Determined crystal structures of monomeric kinesin KIF1A in complex with transition-state analogs: adenylyl imidodiphosphate (AMP-PNP), ADP-vanadate, and ADP-AlFx.
• Compared these structures with existing ADP- and AMP-PCP-bound states.

Main Results:

• Kinesin utilizes two microtubule-binding loops (L11 and L12) in an alternating fashion.
• Loop L11 is extended in the AMP-PNP bound state, while loop L12 is extended in the ADP bound state.
• ADP-vanadate reveals an intermediate state where both loops are raised, facilitating active detachment from microtubules.

Conclusions:

• Kinesin's mechanical cycle involves dynamic conformational changes in switch regions.
• Alternating extension and retraction of microtubule-binding loops mediate kinesin's movement and detachment.
• Structural insights into transition states provide a detailed understanding of kinesin's energy transduction mechanism.