Figure 4. A region of the basigin-1 Ig0 domain with sequence homology to L1cam binds to basigin-2. A: A sequence comparison of the basigin-1 Ig0 domain and the L1cam is shown. Identical amino acids are indicated, and homologous amino acids are highlighted. B: Binding assays were performed using the Ig0–6XHis, Ig0L1–6XHis, and L1cam-6XHis recombinant proteins with endogenous basigin captured from the mouse neural retina. C: An affinity binding curve was generated using serial dilutions of Ig0L1–6XHis from 5 μM to 0.3125 μM with endogenous basigin gene products captured from the mouse neural retina. D: Binding assays were performed using the Ig0L1–6XHis (black circles) and C-6XHis (white circles) recombinant proteins with endogenous basigin from the mouse neural retina (NR) or BSA (BSA). For the binding assays, the interactions were 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 of the triplicate runs. The error bars represent the standard deviation of the mean. A one-way ANOVA (B) or two-way ANOVA (C) with Tukey’s multiple comparison test was performed. The p values are indicated (α level = 5%). For the affinity curve, 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.