Retinol-binding protein that mediates retinol transport in blood plasma. Delivers retinol from the liver stores to the peripheral tissues. Transfers the bound all-trans retinol to STRA6, that then facilitates retinol transport across the cell membrane. Interacts with TTR (PubMed:2209607). Interaction with TTR prevents its loss by filtration through the kidney glomeruli (Probable). Interacts with STRA6 (PubMed:17255476, PubMed:18419130). Detected in blood plasma (at protein level). Belongs to the calycin superfamily. Lipocalin family.