Crystal Structure of the KIF5C Motor Domain With ADP
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Contents |
Introduction
Proteopedia page made by Urvija Rajeshkumar Agrawal to fulfill 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 [1]
The ADP-bound structure of KIF5C defines a critical intermediate in its ATPase cycle. It captures the motor in a state where nucleotide retention, destabilisation, and eventual release are governed by precise movements within the switch regions and nearby helices.
Nucleotide Pocket Configuration
Switch II and the neck-linker remain arranged similarly to ATP-like kinesin states, but switch I is shifted outward. This displacement rotates helix α3, moving L9 away from the pocket and disrupting the Arg191–Asp232 Mg-stabiliser. Without this stabiliser, Mg-ADP becomes inherently unstable, priming the motor for microtubule-stimulated nucleotide exchange.
Contrast With MT-Bound Conformations
When KIF5C binds GTP-state GMPCPP microtubules, the motor undergoes a coordinated conformational tightening, switch I closes, α4 rotates inward, L11 elongates to wedge between α4 and α6, and the neck-linker begins docking. These transitions are absent in the ADP structure and define the rigour-like, strong-binding state required for rapid ADP release.
Functional Relevance of L11
L11, flexible and undocked in the ADP state, emerges as a central determinant of microtubule nucleotide-state sensing. Mutations in L11 abolish KIF5C’s preference for GTP-state microtubules and reduce MT-activated ATPase activity.
Conclusion
The ADP structure provides a mechanistic baseline, clarifying how GTP-state microtubule recognition reshapes the KIF5C motor into its force-generating form. Because GTP-state lattices are enriched in axons relative to dendrites, this structural preference directly explains why KIF5C selectively enters axons and not dendrites. Accordingly, the ADP-bound conformation represents a primed intermediate that supports polarised neuronal transport upon recognition of the appropriate microtubule substrate.
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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
