Cryo-EM Reveals the Chemo-Mechanical Coupling of the Oncogenic Kinesin-3 KIF14

KIF14 is a member of the kinesin-3 family that is involved in cell division. It localizes to the mitotic spindle during anaphase and to the midbody during cytokinesis. It is considered an oncogene as its overexpression causes proliferation and poor prognosis in breast and other cancers [1]. However, the role of KIF14 during cell division and its molecular action mechanism are still poorly understood. It was shown previously that KIF14 is a slow plus-end-directed motor that can stabilize microtubules in vitro [2]. To understand structurally the chemo-mechanical cycle of this kinesin and its relationship with microtubule stability we compared by cryo-EM constructs of mouse KIF14 in multiple nucleotide states. Three distinct constructs containing the KIF14 motor domain were designed with different lengths on the C-terminal end. The 3D structures of each of the 3 constructs were obtained by cryo-EM in several nucleotide states. The high resolution EM maps obtained reveal nucleotide specific structural changes that are coupled with the neck-linker docking. The structural changes observed correlate with the differences observed in functional assays designed to study microtubule binding and stabilization. Altogether the results provide a near-atomic model of the chemo-mechanical cycle of KIF14 that accounts for its in vitro properties. The structures also resolve general structural features that are key for the function of other motile kinesins. 1. Corson, T.W. and B.L. Gallie, KIF14 mRNA expression is a predictor of grade and outcome in breast cancer. International Journal of Cancer, 2006. 119(5): p. 1088-1094. 2. Arora, K., et al., KIF14 Binds Tightly to Microtubules and Adopts a Rigor-Like Conformation. Journal of Molecular Biology, 2014. 426(17): p. 2997-3015.