Model: The β-CTT interacts with the kinesin-5 N-terminus to promote motility. (A) Spindle localization of kinesin-5 reaches maximum prior to anaphase onset with higher levels of Cin8 relative to Kip1. The β-CTT increases Cin8 spindle localization. During spindle elongation in anaphase, the β-CTT increases Cin8 motility and promotes midzone localization. (B) Interactions between the β-CTT and Cin8 N-terminus increase Cin8 localization to microtubules. (C) Then, during the Cin8 mechanochemical cycle, this interaction could promote the binding of the forward motor domain, increasing the Cin8 velocity. (D) Finally, this interaction could help release the trailing motor domain as well as maintain the association between the motor domain and microtubules within the midzone during spindle elongation.