Structure of N-linked oligosaccharide chains in the triple-helical domains of human type VI and mouse type IV collagen.

Asparagine-linked oligosaccharides were liberated from pepsin-treated type VI collagen and the 7S domain of type IV collagen by hydrazinolysis and their structures analysed by exoglycosidase treatment. The major component in both proteins was complex biantennary oligosaccharide being partly modified by the addition of fucose and sialic acid residues. The 7S domain contained in addition distinct amounts of truncated biantennary structures lacking one or two beta-galactose residues and a minor triantennary structure. Carbohydrate analysis indicated that all of the N-linked and 80-90% of the O-linked acceptor sites are occupied. The lack of galactosamine content in both collagens showed the O-linked oligosaccharides were only those attached to hydroxylysine and not to serine or threonine. The high carbohydrate density along both triple helical domains is discussed with regard to their limited ability to form lateral aggregates.