Kinesin that supports microtubule movement in an ATP- dependent manner and that functions as a minus-end directed motor as well as a plus-end tracking protein. During mitosis; is involved in early spindle assembly. Participates in the capture of antiparallel interpolar microtubules and helps in generating force to coalign microtubules. {ECO:0000269|PubMed:15659646; ECO:0000269|PubMed:17220198}.