Kinesin has three nucleotide-dependent conformations. Implications for strain-dependent release

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Limited crystallographic data exists for nucleotide-bound states of kinesin, hindering understanding of its ATPase cycle.
• Previous studies focused on myosin, leaving kinesin's structural dynamics less understood at a molecular level.

Purpose of the Study:

• To investigate the molecular-level structural changes in human kinesin motor domain during its ATPase cycle.
• To characterize the communication between catalytic and microtubule-binding sites in kinesin.

Main Methods:

• Production of single tryptophan mutants in monomeric human kinesin motor domain.
• Utilizing fluorescence resonance energy transfer (FRET) to measure intramolecular distances in different binding states.
• Performing kinetic studies of fluorescent nucleotide binding.

Main Results:

• Mutants exhibited nucleotide-dependent microtubule affinity changes similar to wild-type kinesin.
• FRET measurements provided direct evidence for the essential role of the switch II loop and helix movement in mediating communication.
• Molecular modeling supported the observed structural communication pathways.
• Kinetic studies indicated that ADP binding induces two distinct structural transitions, differing from ATP binding.

Conclusions:

• Movement of the switch II loop and helix is crucial for kinesin's mechanochemical cycle.
• ADP binding induces unique structural changes, distinct from ATP binding, impacting kinesin's function.
• This research provides a foundation for understanding kinesin's structural dynamics and mechanochemical cycle.