Fine structure of the arabinogalactan-protein from Lolium multiflorum

The extracellular arabinogalactan-protein from suspension-cultured cells of Lolium multiflorum (ryegrass) was purified in a single step by affinity chromatography of the culture medium on myeloma protein J539-Sepharose. The product obtained after two Smith-degradations had an apparent molecular size corresponding to that of galactoheptaose and was mainly (1→3)-linked. The Smith-degradation products were essentially monodisperse with respect to molecular size, indicating that periodate-oxidisable residues were distributed regularly along the polysaccharide chains. The polysaccharide chains in the arabinogalactan-protein were probably attached to hydroxyprolyl residues of the protein core via O-glycosylic linkages. No carbohydrate appears to be linked to serine or threonine residues. No oligo-arabinosides linked to hydroxyproline could be detected. © 1987.