Fig. 6.

Comparison of the binding properties of iodinated WT OS₂ and C-terminal chimera to mouse brain membranes. All of the binding experiments were performed in parallel and on the same membrane preparations (n=3). (A and B), Direct equilibrium binding assays with the two iodinated ligands. Membranes were incubated with various concentrations of labeled ligands in the absence (*) or presence (—) of 100 nM unlabeled homologous ligand. The specific binding (▯) represents the difference between total (*) and non specific binding (—). (C and D), Scatchard plot analysis of the specific binding. (E and F), Competition experiments between iodinated ligands and unlabeled WT recombinant OS₂ and the different chimeras. Membranes were incubated with 50 pM of WT ¹²⁵I-OS₂ or ¹²⁵I-C-terminal chimera and various concentrations of unlabeled competitors. Results are expressed as the percentage of ¹²⁵I-OS₂ specific binding measured in the absence of competitor. The non specific binding was measured in the presence of 100 nM unlabeled homologous ligand and was below 15% of total binding.