Structural model of microtubule dynamics inhibition by kinesin-4 from the crystal structure of KLP-12 –tubulin complex
Shinya Taguchi, Juri Nakano, Tsuyoshi Imasaki, Tomoki Kita, Yumiko Saijo‐Hamano, Naoki Sakai, Hideki Shigematsu, Hiromichi Okuma, Takahiro Shimizu, Eriko Nitta, Satoshi Kikkawa, Satoshi Mizobuchi, Shinsuke Niwa, Ryo Nitta
Abstract
Kinesin superfamily proteins are microtubule-based molecular motors driven by the energy of ATP hydrolysis. Among them, the kinesin-4 family is a unique motor that inhibits microtubule dynamics. Although mutations of kinesin-4 cause several diseases, its molecular mechanism is unclear because of the difficulty of visualizing the high-resolution structure of kinesin-4 working at the microtubule plus-end. Here, we report that KLP-12, a C. elegans kinesin-4 ortholog of KIF21A and KIF21B, is essential for proper length control of C. elegans axons, and its motor domain represses microtubule polymerization in vitro. The crystal structure of the KLP-12 motor domain complexed with tubulin, which represents the high-resolution structural snapshot of the inhibition state of microtubule-end dynamics, revealed the bending effect of KLP-12 for tubulin. Comparison with the KIF5B-tubulin and KIF2C-tubulin complexes, which represent the elongation and shrinking forms of microtubule ends, respectively, showed the curvature of tubulin introduced by KLP-12 is in between them. Taken together, KLP-12 controls the proper length of axons by modulating the curvature of the microtubule ends to inhibit the microtubule dynamics.