Characterization of the asialoglycoprotein receptor in a continuous hepatoma line

The asialoglycoprotein receptor has been identified on a continuous human hepatoma cell line, HepG2. This receptor requires Ca²⁺ for ligand binding and is specific for asialoglycoprotein. There are approximately 150,000 ligand molecules bound/cell at 4° C. These receptors represent a homogeneous population of high affinity binding sites with K[d] = 7 x 10^-9 M. From the rate of ¹²⁵I-ASOR binding at 4°C, k[on] was 0.95 x 10⁶ M^-1 min^-1. Uptake of ¹²⁵I-ASOR at 37°C was approximately 0.02 pmol/min/10⁶ cells.