title: Characterization and distribution of O-glycosylated carbohydrates in the cell adhesion molecule, contact site A, from Dictyostelium discoideum.
abstract: This paper presents further investigation of the properties of carbohydrate II in the cell adhesion molecule, contact site A, from Dictyostelium discoideum. A purified contact site A was digested with Achromobacter protease I to produce a 31-kDa fragment to which carbohydrate II was mainly bound and a 21-kDa fragment containing the NH2 terminus of contact site A, which was identified as Ala-Pro-Thr-Ile-Thr-Ala. The NH2 terminus of the 31-kDa fragment was Thr-Glu-Ala-Thr-Thr-Ser. It was estimated from the cDNA sequence data of contact site A that more than 20 Ser/Thr residues exist as target sites for the O-linked oligosaccharides in the 31-kDa fragment, but not for the N-linked oligosaccharides. These results suggest that carbohydrate II exists as clustered O-linked oligosaccharides in the COOH terminus of contact site A. The results of two-dimensional electrophoresis confirm that oligosaccharides of contact site A contain sialic acids. Immunoelectron microscopy was carried out to define the organelle in which O-glycosylation by carbohydrate II occurs and how carbohydrate II antigens are distributed on the cell surface. The results show that O-glycosylation can occur in the Golgi apparatus in D. discoideum as observed in other cells, although this O-glycosylation was inhibited by tunicamycin. Furthermore, gold particles were densely concentrated in cell-cell contact regions but sparsely distributed in noncontact regions.
authors.affiliation: Research Institute of Food Science, Kinki University, Higashi-Osaka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yoshida
authors.forename: S
authors.initials: S
authors.lastname: Yokota
authors.forename: S
authors.initials: S
authors.lastname: Ouchi
mesh_terms: D000818:Animals; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism*; D004023:Dictyostelium / Q000378:metabolism*; D006031:Glycosylation; D016253:Microscopy, Immunoelectron; D010446:Peptide Fragments / Q000032:analysis; D010835:Phytohemagglutinins / Q000494:pharmacology; D015800:Protozoan Proteins; D012794:Sialic Acids / Q000378:metabolism
chemical_list: D002241:Carbohydrates; D015815:Cell Adhesion Molecules; D010446:Peptide Fragments; D010835:Phytohemagglutinins; D015800:Protozoan Proteins; D012794:Sialic Acids; C052291:cell cohesion molecule, Dictyostelium; C100156:leukoagglutinins, plants