KLIF (Kinesin-Like Intermediate Filament-associated protein) functions as a novel microtubule (MT)-organizing motor, essential for cytokinesis in Trypanosoma brucei by bundling and aligning microtubules to define the new posterior end of the cell.
It operates as a non-motile or slow-motile kinesin that organizes MT networks through the following mechanisms:
Crosslinking and Parallel Bundling: KLIF acts as a crosslinker that sorts microtubules into parallel bundles. While it can crosslink antiparallel microtubules and cause them to slide relative to one another, it keeps parallel-oriented microtubules static, leading to the formation of stable, ordered parallel bundles.
Plus-End Stabilization: KLIF stabilizes the alignment of microtubule plus ends, acting as an organizing center that gathers these ends together.
Structural Composition: The functional unit is a parallel dimer. It possesses an intrinsically disordered N-terminal extension that acts as a secondary microtubule-binding domain, which is essential for its bundling activity.
Slow Motor Activity: The KLIF motor domain contains specific active site mutations—common in other MT-organizing motors—that slow down its motor activity while enhancing its ability to bundle microtubules.
In summary, KLIF acts as a structural organizer that uses its dimeric, crosslinking nature to create stable, aligned bundles of microtubules, essential for cell shape maintenance and division. If you’d like, I can:
Compare KLIF to other known MT-organizing kinesins (like kinesin-14).
Describe the role of KLIF in T. brucei cell division more specifically.
Explain the role of the “intrinsically disordered N-terminal extension” in more detail.