F Type Retinoid Binding Protein:Proteins which bind with retinol. The retinol-binding protein found in plasma has an alpha-1 mobility on electrophoresis and a molecular weight of 21,000-22,000. The protein has one binding site for retinol and is responsible for the transport of Vitamin A. The retinol- protein complex (molecular weight 80,000 to 90,000) circulates in plasma in the form of a protein-protein complex with prealbumin. The retinol-binding protein found in tissue has a molecular weight of 14,000 and carries retinol as a non-covalently-bound ligand.