The protein encoded by this gene acts as a heterodimer with kinesin family member 3A to aid in chromosome movement during mitosis and meiosis. The encoded protein is a plus end-directed microtubule motor and can interact with the SMC3 subunit of the cohesin complex. In addition, the encoded protein may be involved in the intracellular movement of membranous organelles. This protein and kinesin family member 3A form the kinesin II subfamily of the kinesin superfamily.