Involved in synaptic functions in photoreceptor cells, the signal transduction in immune cells as a Src family kinase activator, endosome recycling, the uptake of bacteria and endocytosis, protein trafficking in sensory neurons and as lipid-binding chaperone with specificity for a diverse subset of myristoylated proteins. Specifically binds the myristoyl moiety of a subset of N-terminally myristoylated proteins and is required for their localization. Binds myristoylated GNAT1 and is required for G-protein localization and trafficking in sensory neurons. Probably plays a role in trafficking proteins in photoreceptor cells. Plays important roles in mediating Src family kinase signals for the completion of cytokinesis via RAB11A. Interacts with CABP4; in the absence of calcium (By similarity). Interacts with DNM1; leading to a decrease of DNM1 GTPase activity (By similarity). May interact with GTP-bound ARL1. Interacts with ARL2 and ARL3 (GTP-bound forms); this promotes the release of myyristoylated cargo proteins (PubMed:22960633, PubMed:30945270). Found in a complex with ARL3, RP2 and UNC119; RP2 induces hydrolysis of GTP ARL3 in the complex, leading to the release of UNC119. Interacts with NPHP3 (when myristoylated). Interacts with CYS1 (when myristoylated). Interacts with MACIR; interaction only takes place when UNC119 is not liganded with myristoylated proteins. Interacts with LCK; this interaction plays a crucial role in activation of LCK. Interacts with FYN. Interacts with RAB11A; in a cell cycle-dependent manner. Interacts with LYN (via SH2 and SH3 domains); leading to LYN activation. Found in a complex with ABL1, ABL2, CRK and UNC119; leading to the inhibition of CRK phosphorylation by ABL kinases. Interacts with CD44; leading to Shigella invasion. Interacts with KLHL18 (via kelch repeats) (PubMed:31696965). Interacts with PPP3CA, PPP3CB and PPP3CC (By similarity). Localizes to the centrosome in interphase cells and begins to translocate from the spindle pole to the spindle midzone after the onset of mitosis; it then localizes to the intercellular bridge in telophase cells and to the midbody in cytokinetic cells. Abundantly expressed in retina, in photoreceptor synapses and inner segments. Expressed in a much lesser extent in several other tissues. Adopts an immunoglobulin-like beta-sandwich fold forming a hydrophobic cavity that captures N-terminally myristoylated target peptides (PubMed:21642972). Phe residues within the hydrophobic beta sandwich are required for myristate binding (PubMed:22085962). Phosphorylation suppresses its interaction with KLHL18 and down-regulates its KLHL18-mediated degradation (PubMed:31696965). Phosphorylated more under light conditions than dark conditions (PubMed:31696965). Dephosphorylated by calcineurin (PubMed:31696965). Defects in UNC119 may be a cause of cone-rod dystrophy. A mutation was found in a 57-year-old woman with late-onset cone-rod dystrophy: from 40 year old, the patient suffered from poor night vision, defective color vision and light-sensitivity. At 57 year old, she displayed reduced visual acuity, myopa, macular atrophy and pericentral ring scotomas. The disease was caused by a heterozygous mutation causing premature termination and truncated UNC119 protein with dominant-negative effect. The disease is caused by variants affecting the gene represented in this entry. Belongs to the PDE6D/unc-119 family. According to some authors, acts by extracting target proteins from membranes (PubMed:21642972). According to a another report, rather acts by targeting proteins to membranes (PubMed:22085962).