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Updated: Aug 25, 2026
Preparation of Segmented Microtubules to Study Motions Driven by the Disassembling Microtubule Ends
Published on: March 15, 2014
Structure of a kinesin microtubule depolymerization machine
Krista Shipley1, Mohammad Hekmat-Nejad, Jennifer Turner
1Graduate Group in Biophysics, University of California, San Francisco, CA, USA.
Abstract:
With their ability to depolymerize microtubules (MTs), KinI kinesins are the rogue members of the kinesin family. Here we present the 1.6 A crystal structure of a KinI motor core from Plasmodium falciparum, which is sufficient for depolymerization in vitro. Unlike all published kinesin structures to date, nucleotide is not present, and there are noticeable differences in loop regions L6 and L10 (the plus-end tip), L2 and L8 and in switch II (L11 and helix4); otherwise, the pKinI structure is very similar to previous kinesin structures. KinI-conserved amino acids were mutated to alanine, and studied for their effects on depolymerization and ATP hydrolysis. Notably, mutation of three residues in L2 appears to primarily affect depolymerization, rather than general MT binding or ATP hydrolysis. The results of this study confirm the suspected importance of loop 2 for KinI function, and provide evidence that KinI is specialized to hydrolyze ATP after initiating depolymerization.
Insights
KinI kinesins depolymerize microtubules through unique structural features. This study reveals the crystal structure of a Plasmodium falciparum KinI motor, highlighting loop 2
Area of Science:
- Molecular Biology
- Structural Biology
- Parasitology
Background:
- KinI kinesins are a unique class of motor proteins known for their ability to depolymerize microtubules (MTs).
- Understanding their distinct mechanism is crucial for comprehending kinesin family diversity and function.
Purpose of the Study:
- To elucidate the structural basis of KinI kinesin's microtubule depolymerization activity.
- To investigate the role of specific structural regions in KinI function, including ATP hydrolysis and MT depolymerization.
Main Methods:
- Determined the 1.6 Å crystal structure of the KinI motor core from Plasmodium falciparum (pKinI).
- Performed site-directed mutagenesis of conserved KinI residues to assess functional impacts.
- Assayed depolymerization activity and ATP hydrolysis rates in vitro.
Main Results:
- The pKinI structure, lacking nucleotide, shows significant differences in loop regions compared to other kinesins, particularly L2 and L10.
- Mutagenesis of three residues in loop 2 specifically impaired depolymerization without affecting general MT binding or ATP hydrolysis.
- KinI kinesins appear specialized to hydrolyze ATP subsequent to initiating microtubule depolymerization.
Conclusions:
- Loop 2 is critical for the depolymerization function of KinI kinesins.
- The structural and functional data suggest a specialized mechanism for KinI-mediated microtubule disassembly.
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