Expression and Mutagenesis of Retinol-Binding Protein

Vitamin A is transported in the plasma as retinol bound to a carrier protein, called retinol-binding protein (RBP), which itself forms a complex with the thyroxine-binding protein, known as transthyretin (TTR). This complex exists in equilibrium with free holo-RBP, which can then interact with a specific cell-surface receptor, thereby inducing the release of its retinol to the target cell. Thus, RBP possesses at least three molecular-recogmtion properties it binds retinol and it interacis with both TTR and the cell-surface receptor (for reviews, see refs. 1 and 2 ).