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 (PubMed:21642972). Probably plays a role in trafficking proteins in photoreceptor cells (PubMed:17174953). Plays important roles in mediating Src family kinase signals for the completion of cytokinesis via RAB11A. May interact with GTP-bound ARL1. Interacts with ARL2 and ARL3 (GTP-bound forms); this promotes the release of myristoylated cargo proteins (By similarity). 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 (By similarity). Interacts with CABP4; in the absence of calcium. Interacts with DNM1; leading to a decrease of DNM1 GTPase activity. Interacts with LCK; this interaction plays a crucial role in activation of LCK (By similarity). Interacts with FYN (By similarity). Interacts with RAB11A; in a cell cycle-dependent manner (By similarity). Interacts with LYN (via SH2 and SH3 domains); leading to LYN activation (By similarity). Found in a complex with ABL1, ABL2, CRK and UNC119; leading to the inhibition of CRK phosphorylation by ABL kinases. Interacts with CD44 (By similarity). Interacts with KLHL18 (via kelch repeats). Interacts with PPP3CA, PPP3CB and PPP3CC (PubMed:31696965). ocalizes 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. Localized in photoreceptor synapses in the outer plexiform layer of the retina. Adopts an immunoglobulin-like beta-sandwich fold forming a hydrophobic cavity that captures N-terminally myristoylated target peptides. Phe residues within the hydrophobic beta sandwich are required for myristate binding (By similarity). 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). Mice develop a slowly progressive retinal degeneration, characterized by mottling in the fundus, mild thinning of the photoreceptor layer, and increase in apoptosis as early as 6 months, dramatic acceleration at approximately 17 months, and virtual obliteration of the photoreceptors by 20 months. Phenotypes are due to defects in protein trafficking, such as Gnat1 mislocalization. Belongs to the PDE6D/unc-119 family.