Control of Motor Landing and Processivity by the CAP-Gly Domain in the KIF13B Tail

Abstract

Microtubules are a major component of the eukaryotic cytoskeleton that play crucial roles in diverse cellular process. Posttranslational modifications (PTMs) of tubulin dimers regulate the dynamics and organization of microtubules, as well as the interactions between microtubules and microtubule-associated proteins (MAPs). One unique PTM that occurs on microtubules is the cyclical removal and re-addition of the C-terminal tyrosine of α-tubulin. CAP-Gly (cytoskeleton-associated protein glycine-rich) domain containing proteins specifically recognize tyrosinated microtubules, a property exploited to regulate and spatially localize diverse microtubule effectors. KIF13B is a member of the long-distance transport kinesin-3 family, and the only kinesin motor that contains a conserved C-terminal CAP-Gly domain. What role the CAP-Gly domain plays in KIF13B’s motility along microtubules is unknown. Here, we investigated the interaction between KIF13B’s CAP-Gly domain, and the tyrosinated C-terminal tail domain of α-tubulin. We found that KIF13B’s CAP-Gly domain strongly influences the initial motor-microtubule interaction, as well as the processive motility of KIF13B along microtubules. The effect of the CAP-Gly domain on kinesin-microtubule binding is specific to the nucleotide state of the motor domain, suggesting an interplay between the N-terminal motor domain and C-terminal CAP-Gly domain underlies the KIF13B-microtubule interaction. These results reveal that specialized kinesin tail domains play active roles in the initiation and continuation of motor movement.