Microtubule-based molecular motor that transport intracellular cargos, such as vesicles, organelles and protein complexes. Uses ATP hydrolysis to generate force to bind and move along the microtubule (By similarity). Plays a role in cilia formation (PubMed:32386558). Involved in photoreceptor integrity and opsin trafficking in rod photoreceptors (PubMed:32386558). Transports vesicles containing N-methyl-D-aspartate (NMDA) receptor subunit GRIN2A into neuronal dendrites (By similarity). Heterodimer of KIF3A and KIF3B (By similarity). KIF3A/KIF3B heterodimer interacts with KIFAP3 forming a heterotrimeric (KIF3A/KIF3B/KIFAP3) complex (By similarity). Interacts directly with IFT20 (By similarity). Interacts with the SMC3 subunit of the cohesin complex (PubMed:9506951). Interacts with FLCN (PubMed:27072130). The gene represented in this entry may be involved in disease pathogenesis. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Kinesin family. Kinesin II subfamily.