The structural switch of nucleotide-free kinesin

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Kinesin-1 is a crucial motor protein for intracellular transport.
• Understanding its nucleotide-binding cycle is key to cellular mechanics.
• Structural data for apo-kinesin-1 (without nucleotide) were previously lacking.

Purpose of the Study:

• To elucidate the structural states of apo-kinesin-1.
• To investigate the role of nucleotide release in kinesin-1's function.
• To resolve the structural dynamics of the kinesin-1 nucleotide cycle.

Main Methods:

• Site-directed mutagenesis to create kinesin-1 mutants affecting ADP binding (T87A, T92V).
• X-ray crystallography to determine the structures of apo-kinesin-1 mutants.
• Comparison of mutant structures with wild-type and tubulin-bound states.

Main Results:

• Mutations revealed a dual mechanism for ADP release from kinesin-1.
• Apo-kinesin-1 was found to adopt two distinct conformations.
• Nucleotide-depleted wild-type kinesin-1 also adopted these conformations.

Conclusions:

• Apo-kinesin-1 exists in two conformations when detached from microtubules.
• Microtubule binding induces a conformational change and ADP release, priming for ATP binding.
• This clarifies the structural transitions in the kinesin-1 nucleotide cycle.