STRUCTURAL-ANALYSIS OF N-LINKED OLIGOSACCHARIDE OF MITOGENIC LECTIN-BFROM THE ROOTS OF POKEWEED (PHYTOLACCA-AMERICANA)

The structure of an asparagine (N-) linked oligosaccharide of pokeweed lectin-B (PL-B) and the amino acid sequences around two glycosylation sites were identified. The pyridylamino (PA) oligosaccharide prepared from PL-B was eluted as a single peak on both reversed-phase (RP-) HP LC and size-fractionation (SF-) HPLC, and its structure was estimated to be Man alpha 1-->6(Man alpha 1--> 3)(Xyl beta 1-->2) Man beta 1-4Gl cNAc beta 1-->4(Fuc alpha 1-->3)GlcNAc by a combination of component a nalysis, successive exoglycosidase digestions, IS-MS analysis, and 500 MHz H-1-NMR. Two tryptic glycopeptides were isolated from the reduced and S-pyridylethylated PL-B after gel filtration followed by RP-HPLC, indicating the presence of two glycosylation sites in PL-B. The amino acid sequences around the two glycosylation sites were determined to b e Cys-Gly-Val-Asp-Phe-Gly-Asn(CHO)-Arg.