The binding stoichiometry of human plasma retinol-binding protein to prealbumin.

The stoichiometry of binding between all-trans-retinolretinol-binding protein (RRP) and prealbumin was investigated by means of gel filtration chromatography, electrophoresis, absorption, and circular dichroism. Using protein concentrations of up to 2.0 mg per ml, it was found that under a variety of experimental conditions 1 prealbumin molecule binds 1 to 1.35 molecules of retinal-RRP at pH 7.0 in an 0.033 M sodium phosphate buffer containing 0.1 M NaCl. These results were further supported by hybridization experiments using both all-frans-retinol-RRP and all-frans-3dehydroretinol-RRP and prealbumin. It was found that the free chromophore-RRP molecules were freely exchangeable with the chromophore-RRP molecules which were bound to prealbumin, but the sum total of chromophore-RRP bound to prealbumin was 1: 1 on a molar basis.