Figure 3. The amino half of the basigin-1 Ig0 domain binds to basigin-2. A: Binding assays were performed using the Ig0–6XHis, Ig0N-6XHis, Ig0C-6XHis, and C-6XHis recombinant proteins with endogenous basigin captured from the mouse neural retina. The interaction was measured using an antibody specific to the six-histidine epitope at the C-terminus of the recombinant proteins and a secondary antibody conjugated to alkaline phosphatase (AP). Conversion of the AP substrate to the product was measured at 405 nm, and the absorbance was used as the binding units. The binding units were plotted as the mean from duplicate runs. B: An affinity binding curve was generated using serial dilutions of Ig0N-6XHis from 5 μM to 0.3125 μM with endogenous basigin gene products captured from the mouse neural retina. Interactions were measured as described for the binding assays. Absorbance at 405 nm was used to determine percent binding in reference to the 5 μM sample. The percent binding was plotted as the mean of duplicate runs. The error bars represent the standard deviation of the mean. The equation from the trendline was used to calculate affinity.