Microtubules and associated motor proteins provide an important structural basis for intracellular motility such as organelle transports, mitosis, meiosis, and cilia and flagellar motility. Organelle transports are very important for cellular morphogenesis and activities, conveying and targeting indispensable materials to the correct destination, often at considerable velocities. In order to clarify this trafficking mechanism by motor proteins, systematical search for novel, putative members of this family have been achieved and a series of cDNA, containing consensus sequences encoding both the ATP-binding and the microtubule-binding domains of kinesin heavy chain, were cloned and characterized from murine brain libraries (1–3). They form kinesin superfamily proteins (KIFs). Now, 10 members (KIF1A, KIF1B, KIF2, KIF3A, KIF3B, KIF4, KIF5A, KIF5B, KIF5C, KIFC1, KIFC2, KIFC3) have been identified and characterized (1–10).