Structural Analysis of Conformational Changes in Kinesin and GTP-state Microtubules Upon Binding

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.

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 “rigour” conformation in KIF5C, accelerating ADP release and supporting rapid ATP-dependent motility. Recognition of the GTP-state lattice depends on structural features of α and β-tubulins.

See Kinesin.

spinqualitylabelsall models Crystal Structure of the KIF5C Motor Domain With ADP (PDB code 3x2t) Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D

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 helices.
• The neck-linker initial segment docks adjacent to α6.

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, implying that overall L11 architecture is required for precise microtubule recognition and 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.

Proteopedia Page Contributors and Editors (what is this?)

Urvija Rajeshkumar Agrawal, Michal Harel