ASGR is a heterooligomeric receptor that is abundantly expressed on the sinusoidal surface of the hepatic plasma membrane. It is an endocytic receptor that rapidly binds and internalizes galactose-terminated glycoproteins (asialoglycoproteins or ASGP) from the circulation. The mouse ASGPR belongs to the long-form subfamily of the C-type/Ca2+ dependent lectin family. It is a complex of two noncovalently-linked and highly homologous subunits, a major 42 kDa glycoprotein ASGPR1(MHL-1) and a minor 51 kDa glycoprotein ASGR2 (MHL-2). ASGPR1 is synthesized as a type II transmembrane protein that contains a cytosolic N-terminal domain, a single transmembrane segment, and an extracellular domain which contains two important structural regions. The first is a stalk domain that contributes to noncovalent oligomerization, and the second is a Ca2+-dependent carbohydrate binding domain at the very C-terminus that is unusually stabilized by three ions. The aa sequence of mouse ASGPR1 ECD is 89% and 79% identical to the ASGPR1 ECD of rat and human, respectively.