| Modification Notes |
Members of the oxyserol-binding protein (OSBP) family function as intracellular lipid receptors. OSBPs are involved in lipid metabolism and signal transduction, as well as vesicle transport, and can translocate to the periphery of Golgi membranes when they are bound to oxysterols. ORPs (OSBP-related proteins) belong to a subfamily of OSBPs and consists of ORP-1 and ORP-2. The ORPs have a highly conserved OSBP-type sterol-binding region and a pleckstrin homology domain. They strongly bind to phosphatidic acid and weakly bind to phosphatidylinositol 3-phosphate. Three isoforms of ORP-1 are produced due to alternative splicing. Isoform ORP-1A is expressed only in retina, brain, pineal gland, fetal brain, and cultured retinal pigment epithelial cells, whereas ORP-1B is expressed ubiquitously. |