Crystal Structure of the KIF5C Motor Domain With ADP
From Proteopedia
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Introduction
Proteopedia page made by Urvija Rajeshkumar Agrawal (20231269) to fulfil the credit requirements of BI3323-Aug2025 Structural Biology.
Source - X-ray and Cryo-EM structures reveal mutual conformational changes of Kinesin and GTP-state microtubules upon binding by M Morikawa et. al. [1]
Function
KIF5C is a microtubule-based motor protein that moves along MTs using ATP hydrolysis. It preferentially binds GTP-state microtubules (GMPCPP-MTs) over GDP-taxol-MTs, enabling selective axonal entry in neurons. Binding to the GTP-state MT induces a strong-binding “rigor” conformation in KIF5C, accelerating ADP release and supporting rapid ATP-dependent motility. Recognition of the GTP-state lattice depends on structural features of tubulin, especially the H4–S5 loop of β-tubulin and H11′ of α-tubulin.
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KIF5C Binding to Microtubules
The KIF5C–MT interface comprises three regions: L8, the α4–L11 region, and the C-terminal part of L12, adjacent to H12 of β-tubulin. GMPCPP-MTs strengthen these contacts, while GDP-taxol-MTs distort tubulin loops, weakening binding. KIF5C reshapes the MT lattice upon binding, and MT conformation in turn determines KIF5C affinity and ATPase activation.
Structural States of KIF5C
Cryo-EM structures of KIF5C bound to GMPCPP- MT and GDP-taxol-MT and the crystal structure of nucleotide-free KIF5C, reveal nucleotide-dependent rearrangements in switch I, switch II, helix α3–L9, L11, and the neck-linker.
On GMPCPP-MTs:
- Switch I (α3–L9) adopts a closed state that facilitates Mg²⁺/ADP release.
- Switch II helix α4 rotates toward the MT axis.
- L11 elongates and inserts between α4 and α6.
- The neck-linker initial segment docks.
These changes define the strong-binding rigour conformation.
Role of L11
Loop L11 is essential for discriminating GTP-state from GDP-state MTs. Replacing KIF5C L11 with KIF1A L11 abolishes GTP-state specificity. Triple alanine mutations reduce but do not eliminate it. L11 is also required for the acceleration of MT-activated ATPase.
Mechanochemical Cycle
On GTP-state MTs, KIF5C transitions from a weak Mg·ADP state to the rigour conformation upon ADP release, followed by Mg.ATP entry, neck-linker docking, and the power stroke that advances the motor.
References
- ↑ Morikawa M, Yajima H, Nitta R, Inoue S, Ogura T, Sato C, Hirokawa N. X-ray and Cryo-EM structures reveal mutual conformational changes of Kinesin and GTP-state microtubules upon binding. EMBO J. 2015 Mar 16. pii: e201490588. PMID:25777528 doi:http://dx.doi.org/10.15252/embj.201490588
