Functions in endoplasmic reticulum to Golgi vesicle-mediated transport and regulates the proper organization of the endoplasmic reticulum and the Golgi (PubMed:26077767, PubMed:33103737). Plays a key role in targeting to neuronal dendrites receptors such as HTR1A (By similarity). Also plays a role in primary cilium and sperm flagellum assembly probably through protein transport to these compartments (PubMed:33103737). Interacts with HTR1A (via C-terminus) (By similarity). Interacts with ABCB9 (via TMD0); this interaction allows (but is not essential) the ER-to-Golgi trafficking and strongly depends on a salt bridge within TMD0 (By similarity). Shuttles between the endoplasmic reticulum, the intermediate compartment and the Golgi apparatus. Highly expressed in brain. Expressed in Purkinje cells of the cerebellum. Homozygous knockout mice lacking Yif1b show impaired visual perception associated with retinal dysfunction and optic atrophy while no ventilator defects or increased susceptibility to seizures is observed. Some deficits in fine motor skills and coordination are also observed. Mutant mice have delayed cerebral myelination, enlarged ventricles, and cerebellar atrophy associated with a reduction in the number of Purkinje cells due to neurodegeneration and necrosis. Purkinje cells show fragmentation of the Golgi apparatus, large autophagosome-like vacuoles, and alteration of the endoplasmic reticulum with dilated cisternae. Male knockout mice are infertile due to abnormal spermatozoa flagella that show microtubule disorganization. Primary cilium abnormalities are also observed in cerebellar Purkinje cells and hippocampal pyramidal cells, for instance. Belongs to the YIF1 family.