Recognition of the Nucleotide-Dependent Feature Facilitates the Microtubule End-Binding of MCAK

The growing plus-end is a key regulatory site for microtubule dynamics. MCAK (mitotic centromere-associated kinesin), a microtubule depolymerizing kinesin, is an end-binding regulator of catastrophe frequency. It is intriguing how MCAK specifically binds to dynamic microtubule ends. Here, we measure the end-binding kinetics of MCAK using single-molecule imaging and reveal the end-binding preference. MCAK binds to the entire GTP cap, including the EB cap and the distalmost cap. Further analysis shows that MCAK strongly binds to GTPγS microtubules, suggesting that it could recognize the nucleotide-dependent feature of microtubules. Moreover, the binding preference is independent on the nucleotide state of MCAK, and this feature facilitates the high-affinity end-binding of MCAK. Finally, we show that despite partially sharing the binding regions, MCAK and XMAP215 function in an additive manner, demonstrating a simple logic of how the end-binding regulators work in co-ordination. In all, our results provide novel insights into understanding how MCAK regulates the dynamics of microtubule ends.