pre-printExpressed ubiquitously, PrBP/d functions as chaperone/co-factor in the transport of a subset of prenylated proteins. PrBP/d features an immunoglobulin-like b-sandwich fold for lipid binding, and interacts with diverse partners. PrBP/d binds both C-terminal C15 and C20 prenyl side chains of phototransduction polypeptides and small GTP-binding (G) proteins of the Ras superfamily. PrBP/d also interacts with the small GTPases, ARL2 and ARL3, which act as release factors (GDFs) for prenylated cargo. Targeted deletion of the mouse Pde6d gene encoding PrBP/d resulted in impeded trafficking to the outer segments of GRK1 and cone PDE6 which are predicted to be farnesylated and geranylgeranylated, respectively. Rod and cone transducin trafficking was largely unaffected. These trafficking defects produce progressive cone-rod dystrophy in the Pde6d/ mouse
