The large sialoglycoprotein of human lymphocytes. II. Biochemical features.
Large sialoglycoprotein of human lymphocytes (L-LSGP) from thymocytes and from peripheral blood lymphocytes (PBL) of normal donor and of B chronic lymphocytic leukemia (CLL) patients was purified by affinity chromatography to Maclura pomifera agglutinin (MPA)-Sepharose followed by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). L-LSGP from the three different sources was very similar in amino acid composition. It contained a high proportion of acidic and hydroxy amino acids and also significant amounts of cysteine. No reduction in mobility in SDS-PAGE was noted for unreduced L-LSGP. The molecule may already in its native form have an extended conformation containing either free sulfhydryl groups or small S-S loops not affecting mobility in SDS-PAGE. L-LSGP was found to be highly glycosylated, the thymocyte glycoprotein containing somewhat less carbohydrate by weight (44%) than that of PBL (normal PBL 53% and B CLL 52%). This was due primarily to a lower content of sialic acid. The molecules contained mannose, galactose, N-acetyl galactosamine, N-acetylglucosamine and sialic acid in molar ratios 1.0:3.0:1.1:1.2:1.3 (thymocyte L-LSGP), 1.0:3.8:1.2:1.0:1.7 (PBL L-LSGP) and 1.0:3.5:2.2:1.3:2.8 (B CLL L-LSGP). The weak interaction of L-LSGP with lentil lectin, concanavalin A (Con A) and leucoagglutinin (La), its unchanged mobility in SDS-PAGE after tunicamycin treatment and its high amount of hydroxy amino acids suggest that most carbohydrate chains are O-glycosidically linked to the peptide chain. Native as well as Nase-treated L-LSGP show size microheterogeneity. This is probably due to small chemical differences in the L-LSGP molecules from different lymphocyte subsets.
D000596:Amino Acids / Q000032:analysis; D001402:B-Lymphocytes / Q000032:analysis*; D006801:Humans; D037102:Lectins; D007945:Leukemia, Lymphoid / Q000378:metabolism; D008970:Molecular Weight; D009005:Monosaccharides / Q000032:analysis; D009439:Neuraminidase; D012795:Sialoglycoproteins / Q000097:blood*; D013601:T-Lymphocytes / Q000032:analysis*; D014357:Trypsin; D014415:Tunicamycin / Q000494:pharmacology
D000596:Amino Acids; D037102:Lectins; D009005:Monosaccharides; D012795:Sialoglycoproteins; D014415:Tunicamycin; D009439:Neuraminidase; D014357:Trypsin