title: Effect of glycosylation on the protein pattern in 2-D-gel electrophoresis.
abstract: Single proteins, when analyzed with 2-D-PAGE, often show multiple spots due to PTMs. In gels of human body fluids, the spot patterns facilitate the assignment and identification of the proteins. We analyzed serums from patients with congenital disorders of glycosylation (CDG) in which glycoproteins are strongly impacted and exhibit highly distinguishable spot patterns compared to healthy controls. We detected a typical protein pattern for alpha1-acid glycoprotein (AGP) and transferrin (Trf) that are markers for CDG. AGP contains five glycosylation sites which results in a complex microheterogeneity of the glycoprotein. On the other hand, in Trf, a glycoprotein with only two glycosylation sites, mainly biantennary complex-type-N-linked glycans are bound. We used 2-D-PAGE, MALDI-TOF-MS, and ESI-MS for the analysis of these glycoproteins and their corresponding glycans. In AGP, the heterogenic glycosylation of the different glycosylation sites is responsible for the complex spot pattern. In contrast to AGP, the protein spots of Trf cannot be explained by glycosylation. We found strong evidence that oxidation of cysteine is responsible for the spot pattern. This study contradicts the commonly accepted assumption that the multiple protein spots of Trf observed in 2-D-PAGE are due, as in AGP, to the glycosylation of the protein.
authors.affiliation: Department of Pediatrics, Division of Clinical Chemistry and Biochemistry, University of Zurich, Zurich, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Kleinert
authors.forename: Thomas
authors.initials: T
authors.lastname: Kuster
authors.forename: Daniel
authors.initials: D
authors.lastname: Arnold
authors.forename: Jaak
authors.initials: J
authors.lastname: Jaeken
authors.forename: Claus W
authors.initials: CW
authors.lastname: Heizmann
authors.forename: Heinz
authors.initials: H
authors.lastname: Troxler
mesh_terms: D002239:Carbohydrate Metabolism, Inborn Errors / Q000097:blood / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods; D006031:Glycosylation; D006801:Humans; D009961:Orosomucoid / Q000032:analysis; D011134:Polysaccharides / Q000032:analysis; D020543:Proteome / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014168:Transferrin / Q000032:analysis
chemical_list: D009961:Orosomucoid; D011134:Polysaccharides; D020543:Proteome; D014168:Transferrin