The chromokinesin Kid (KIF22) forms a homodimer, moves processively along microtubules, and transports double-stranded DNA

During prometaphase in mitosis, chromosomes are moved toward the spindle equator. The chromokinesin Kid, also known as KIF22, plays a role in this process by moving chromosomes along spindle microtubules. Traditionally, Kid was thought to be a monomeric and nonprocessive motor, distinct from typical kinesins. However, a recent study reveals that the full-length Kid forms a homodimer and exhibits processive movement along microtubules.

A conserved coiled-coil domain within the stalk region of Kid is sufficient for this homodimer formation and is essential for its processivity. Additionally, the neck linker and coiled-coil domains of Kid can enhance the processive activity of the motor domain of KIF1A. This suggests that Kid possesses both a functional neck linker and dimerization capability, which are vital for kinesin motor domain processivity.

Furthermore, the full-length Kid, containing a helix–hairpin–helix domain, has been found to transport double-stranded DNA along microtubules in vitro. According to AlphaFold3 prediction, the dimerization of Kid stabilizes its association with DNA. Collectively, these findings challenge the previous classification of Kid as a nonprocessive monomer and propose a reclassification as a processive and dimeric motor that transports DNA along microtubules.