KIF1B, A NOVEL MICROTUBULE PLUS END-DIRECTED MONOMERIC MOTOR PROTEIN FOR TRANSPORT OF MITOCHONDRIA

To further elucidate the mechanism of organelle transport, we cloned a navel member of the mouse kinesin superfamily, KIF1B. This N-terminal -type motor protein is expressed ubiquitously in various kinds of tiss ues. In situ hybridization revealed that KIF1B is expressed abundantly in differentiated nerve cells. Interestingly, KIF1B works as a monome r, having a microtubule plus end-directed motility, Our rotary shadowi ng electron microscopy revealed mostly single globular structures. Imm unocytochemically, KIF1B was colocalized with mitochondria in vivo. Fu rthermore, a subcellular fractionation study showed that KIF1B was con centrated in the mitochondrial fraction, and purified KIF1B could tran sport mitochondria along microtubules in vitro. These data strongly su ggested that KIF1B works as a monomeric motor for anterograde transpor t of mitochondria.