抄録
A binding protein specific for asialoglycoproteins was isolated from rat liver by affinity chromatography. The protein is composed of a single glycoprotein with an estimated molecular weight of 52, 000 in which sialic acid, galactose, mannose, and glucosamine make up 10% of the total molecule. The binding activity of the rough microsomes was one third that of the smooth microsomes. Rough and smooth microsomes were digested with trypsin and neuraminidase and also incubated with the antibody to the binding protein in the absence or presence of Triton X-100. Without Triton X-100, 25-30% and 50% of the binding activity of the rough and smooth microsomes, respect-ively, were always protected from digestion by the enzymes or were freed from inhibition by the antibody. In the presence of Triton X-100, trypsin inactivated 100%, but neuraminidase inactivated 80% and 70% of the binding activity of the rough and smooth microsomes. These results suggest that the binding activity on the luminal side of the microsomal membrane is due to the precursor form(s) of the binding protein.
