Hohmann, H. P. and Bozzaro, S. and Yoshida, M. and Merkl, Rainer and Gerisch, G. (1987) Two-step Glycosylation of the Contact Site A Protein of Dictyostelium discoideum and Transport of an Incompletely Glycosylated Form to the Cell Surface. The Journal of Biological Chemistry 262 (34), pp. 16618-16624.
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Two different types of oligosaccharides, designated type 1 and 2 carbohydrate residues, are present on the contact site A molecule, an 80-kDa glycoprotein involved in the formation of EDTA-stable cell adhesion during cell aggregation in Dictyostelium discoideum. The first precursor detected by pulse-chase labeling with [35S]methionine was a 68-kDa glycoprotein carrying type 1 carbohydrate. Conversion of the precursor into the 80-kDa form occurred simultaneously with the addition of type 2 carbohydrate. Tunicamycin inhibited type 1 glycosylation more efficiently than type 2 glycosylation. The first precursor detected in tunicamycin-treated cells by pulse-chase labeling was a 53-kDa protein lacking both carbohydrates, which was converted through addition of type 2 carbohydrate into a 66-kDa final product. Labeling of intact cells indicated that this 66-kDa glycoprotein is transported to the cell surface. Prolonged treatment with tunicamycin resulted in the accumulation within the cells of the 53-kDa precursor with no detectable exposure of this protein on the cell surface. It is concluded that type 1 carbohydrate, which is cotranslationally added in N-glycosidic linkages, is neither required for transport of the protein to the Golgi apparatus nor for type 2 glycosylation or protection of the protein against proteolytic degradation. Incapability of tunicamycin-treated cells of forming EDTA-stable cell contacts suggests a role for type 1 carbohydrate in cell adhesion. Type 2 carbohydrate is added posttranslationally. It is required in the absence of type 1 glycosylation for transport of the protein to the cell surface.
|Institutions:||Biology, Preclinical Medicine > Institut für Biophysik und physikalische Biochemie > Prof. Dr. Reinhard Sterner > Arbeitsgruppe PD Dr. Rainer Merkl|
|Keywords:||Antibodies, Monoclonal Biological Transport, Active Carbohydrates/analysis Concanavalin A/metabolism Dictyostelium/*analysis Fluorescent Antibody Technique Glycosylation Molecular Weight Support, Non-U.S. Gov't Surface Properties Viral Proteins/*metabolism Wheat Germ Agglutinins/metabolism|
|Subjects:||500 Science > 570 Life sciences|
|Refereed:||Yes, this version has been refereed|
|Created at the University of Regensburg:||No|
|Deposited On:||16 Nov 2009 10:36|
|Last Modified:||21 Dec 2009 07:46|