Retinol Binding Protein 5, Cellular (RBP5)

The deduced 135-amino acid protein has a calculated molecular mass of 15.9 kD and shares 55.6% and 49.6% amino acid identity with RBP1 and RBP2, respectively. RNA dot-blot analysis of human tissues detected strong expression of RBP5 in adult kidney and liver with weak expression in fetal spleen, adult spleen, lymph node, appendix, fetal liver, and fetal kidney. Comparison of hybridization signals showed that RBP5 transcript levels in kidney and liver exceeded those of RBP1 by approximately 200 and 13 times, respectively.RBP5 bound all-trans retinol, and they suggested that RBP5 binds the retinol ligand with a specific interaction similar to that observed in the retinol-RBP1 complex. They estimated a binding of 0.66 mol of retinol ligand per mol of RBP5 and apparent Kd of 60 nM.