Glycoproteins with N-acetylglucosamine and mannose residues in Chinese hamster metaphase chromosomes.

Abstract

Distribution of glycosylated proteins in Chinese hamster metaphase chromosomes was studied with fluorescein isothiocyanate conjugated lectins. Three substructural domains with distinct glycoprotein compositions were identified. In situ binding of the lectins Wheat germ agglutinin (WGA) and Datura stramonium agglutinin (DSA) showed that chromosomal proteins containing N-acetylglucosamine residues preferentially localize to the surface domain and the helically coiled substructure of chromatids. In Western blots, digoxigenin conjugated WGA and DSA bound to several chromosomal proteins with molecular weight ranges of 45-220 kD and 66-220 kD, respectively. Binding of Galanthus nivalis agglutinin revealed that mannosylated chromosomal proteins are enriched at the surface and G/Q band domains, and their molecular weights range from 97 to 200 kD. The carbohydrate side chain structure of these mannosylated proteins must be quite specific, as after binding of another mannose-specific lectin, Concanavalin A, only a faint fluorescence was observed in metaphase chromosomes and only one protein band of 185 kD was weakly stained in Western blots. These data suggest that chromosomal glycoproteins containing N-acetylglucosamine and mannose residues play a role in the higher order structural organization of metaphase chromosomes.