BACKGROUND: Kinesin-3 family motors drive diverse cellular processes and have significant clinical importance. The ATPase cycle is integral to the processive motility of kinesin motors to drive long-distance intracellular transport. Our previous work has demonstrated that kinesin-3 motors are fast and superprocessive with high microtubule affinity. However, chemomechanics of these motors remain poorly understood.
RESULTS: We purified kinesin-3 motors using the Sf9-baculovirus expression system and demonstrated that their motility properties are on par with the motors expressed in mammalian cells. Using biochemical analysis, we show for the first time that kinesin-3 motors exhibited high ATP turnover rates, which is 1.3- to threefold higher compared to the well-studied kinesin-1 motor. Remarkably, these ATPase rates correlate to their stepping rate, suggesting a tight coupling between chemical and mechanical cycles. Intriguingly, kinesin-3 velocities (KIF1A > KIF13A > KIF13B > KIF16B) show an inverse correlation with their microtubule-binding affinities (KIF1A < KIF13A < KIF13B < KIF16B). We demonstrate that this differential microtubule-binding affinity is largely contributed by the positively charged residues in loop8 of the kinesin-3 motor domain. Furthermore, microtubule gliding and cellular expression studies displayed significant microtubule bending that is influenced by the positively charged insert in the motor domain, K-loop, a hallmark of kinesin-3 family.
CONCLUSIONS: Together, we propose that a fine balance between the rate of ATP hydrolysis and microtubule affinity endows kinesin-3 motors with distinct mechanical outputs. The K-loop, a positively charged insert in the loop12 of the kinesin-3 motor domain promotes microtubule bending, an interesting phenomenon often observed in cells, which requires further investigation to understand its cellular and physiological significance.
Bibliographical noteFunding Information:
V.S. acknowledges funding through DBT (Grant No.: BT/PR15214/BRB/10/1449/2015 and BT/RLF/Re-entry/45/2015) and DST-SERB (Grant No.: ECR/2016/000913). P.K.N acknowledges ICMR for funding (Grant No. 5/13/13/2019/NCD-III). P.S. acknowledges funding from DST (Grant No.: SR/WOS-A/LS-73/2017). N.M.P and D.J.S acknowledges fellowship from IIT Gandhinagar.
© 2022, The Author(s).
- Microtubule bending
- Adenosine Triphosphate/metabolism
- Adenosine Triphosphatases/analysis
- Protein Binding
PubMed: MeSH publication types
- Research Support, Non-U.S. Gov't
- Journal Article