Carbohydrate structures of the third component of rat complement. Presence of both high-mannose and complex type oligosaccharide chains.
We investigated the carbohydrate structure of the third component of complement (C3) newly synthesized by cultured rat hepatocytes. When the cells were incubated with [3H]mannose, [3H]galactose or [3H]glucosamine, these radioactive precursors were incorporated only into the alpha subunit of C3, demonstrating that only the alpha subunit contains oligosaccharide chains. [3H]Mannose-labelled C3 was purified from the culture medium by immunoaffinity chromatography. Oligosaccharides prepared by Pronase digestion and strong alkaline hydrolysis were separated into two fractions by Bio-Gel P-2 chromatography (Fractions I and II). The two fractions were analysed by concanavalin A-Sepharose chromatography, ion-exchange high-performance liquid chromatography, and Bio-Gel P-4 gel filtration before and after sequential exoglycosidase digestions. It was found that Fraction I contained two complex type oligosaccharide chains, (NeuAc)2(Gal)2(GlcNAc)2(Man)3(GlcNAc)2 and (NeuAc)3(Gal)3(GlcNAc)3(Man)3(GlcNAc)2, and Fraction II contained the high-mannose type, consisting mainly of (Man)8(GlcNAc)2. Taken together with the carbohydrate composition of rat serum C3, the results suggest that rat C3 has one high-mannose type oligosaccharide chain and two complex type chains in the alpha subunit, which is different from the proposal for human C3.
D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D002850:Chromatography, Gel; D003176:Complement C3; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D008358:Mannose / Q000032:analysis*; D009844:Oligosaccharides / Q000032:analysis*; D051381:Rats
D002241:Carbohydrates; D003176:Complement C3; D009844:Oligosaccharides; D008358:Mannose