Myristoyl-binding protein that acts as a cargo adapter: specifically binds the myristoyl moiety of a subset of N-terminally myristoylated proteins and is required for their localization. Binds myristoylated NPHP3 and plays a key role in localization of NPHP3 to the primary cilium membrane. Does not bind all myristoylated proteins. Probably plays a role in trafficking proteins in photoreceptor cells (By similarity). Found in a complex with ARL3, RP2 and UNC119B; RP2 induces hydrolysis of GTP ARL3 in the complex, leading to the release of UNC119B. Interacts with NPHP3 (when myristoylated). Interacts with CYS1 (when myristoylated). Interacts with MACIR; interaction only takes place when UNC119B is not liganded with myristoylated proteins (By similarity). Enriched at the transition zone and extended into the proximal end of the cilium. Adopts an immunoglobulin-like beta-sandwich fold forming a hydrophobic cavity that capture N-terminally myristoylated target peptides. Phe residues within the hydrophobic beta sandwich are required for myristate binding (By similarity). Belongs to the PDE6D/unc-119 family.