Function
Retinol-binding protein (RBP) are carrier proteins which bind retinol (vitamin A alcohol). Human RBP4 is the carrier of retinol in the blood. It delivers retinol from the liver to the peripheral tissues. RBP also functions in regulation, metabolism and activities of retinoids. Retinol is being protected from oxidation and becomes soluble when bound to RBP. RBP is classified according to its site of activity. Plasma RBP (PRBP) carries retinol in blood[1] while cellular RBP (CRBP) carries retinol in the cell[2].
- Interphotoreceptor retinoid-binding protein (iRBP) is involved in the regeneration of rhodopsin in the visual cycle[3].
Relevance
RBP is used to assess vitamin A deficiency as it binds 1:1 to retinol[4]. RBP IV is used as biomarker for renal dysfunction and cardiovascular disease in type II diabetes[5].
Structural highlights
[6]. . Water molecules are shown as red spheres.
3D structures of retinol-binding protein
Retinol-binding protein 3D structures