Fig. 1. Mesd binds to mature LRP6 at the cell surface with high affinity. (A) Time course of ¹²⁵I-Mesd (5 nM) binding to LRP6-transduced HT1080 cells and the control cells. Assay was carried out for the indicated periods at 4°C in the absence (total) or presence of 500 nM Mesd (non-specific). (B) Saturation binding of ¹²⁵I-Mesd to LRP6-transduced HT1080 cells and the control cells. Assay was carried out at indicated concentrations for 3 hours at 4°C in the absence (total) or presence (non-specific) of 500 nM Mesd. (C) Scatchard plots of data in B. All values are the average of triple determinations with the s.d. indicated by error bars.