MCAK recognizes the nucleotide-dependent feature at growing microtubule ends.

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 growing microtubule ends. Here, we measure the end-binding kinetics of MCAK using single-molecule imaging and reveal that MCAK not only binds to the distalmost ends, but also to the proximal region of GTP cap where EB1 preferentially binds. Further analysis shows that MCAK strongly binds to GTPγS microtubules which mimic the GDP·Pi-tubulin-enriched region of GTP cap, and this binding preference is dependent on the nucleotide state of MCAK. This finding suggests that MCAK recognizes the nucleotide-dependent feature of microtubule ends. Moreover, we show that although MCAK and XMAP215 partly share binding regions at the distalmost ends, they act largely independently, influencing catastrophe frequency and growth rate, respectively. Overall, our findings provide new insights into how MCAK regulates microtubule end dynamics.