Chemical and physical properties of an hepatic membrane protein that specifically binds asialoglycoproteins.

The state of aggregation found in water-soluble preparations of an hepatic membrane protein responsible for the clearance of serum asialoglycoproteins has been shown to result from the self-associating properties of a single oligomeric protein. The smallest functional unit identifiable in aqueous solution possessed an estimated molecular weight of 500,000 with each of the successive components increasing in size by an equal amount to form an oligomeric series bearing an integral ratio of 1:2:3:4:5. The tendency towards self-association was promptly and completely reversed by the addition of Triton X-100 with the concomitant appearance of a single component. Extensive treatment with sodium dodecyl sulfate permitted the identification and isolation of two subunits with estimated molecular weights of 48,000 and 40,000, respectively. Amino acid and carbohydrate analyses revealed both subunits to be glycoproteins with a closely similar, but not identical, composition.