Binding of 11-cis retinaldehyde to the partially purified cellular retinaldehyde binding protein from bovine retinal pigment epithelium.

11-cis retinaldehyde binding analysis was performed on a bovine retinal pigment epithelium preparation of cellular retinaldehyde binding protein (CRALBP), whose purity degree was estimated as 75%. Equilibrium binding studies were carried out measuring the replacement of tritium-labeled with unlabeled 11-cis retinaldehyde at 25 degrees C. Analysis of the experimental data both by a direct curve-fitting procedure utilizing a non linear least square regression analysis and by a conventional Scatchard plot revealed a single non-interacting binding site with an apparent equilibrium constant of 0.9 X 10(-7) M. A binding stoichiometry of approximately 1 mol of 11-cis retinaldehyde/mol of binding protein can be calculated from the experimental data. Competition studies carried out in the presence of unlabeled 'trans' and 'cis' isomers of vitamin A derivatives confirm the high degree of specificity of the 11-cis retinaldehyde binding.