Mass spectrometric identification of N- and O-glycosylation sites of full-length rat selenoprotein P and determination of selenide-sulfide and disulfide linkages in the shortest isoform.

Ma S, Hill KE, Burk RF, Caprioli RM
Biochemistry. 2003 42 (32): 9703-11

PMID: 12911312 · DOI:10.1021/bi0346300

Rat selenoprotein P is an extracellular glycoprotein of 366 amino acid residues that is rich in cysteine and selenocysteine. Plasma contains four isoforms that differ principally by length at the C-terminal end. Mass spectrometry was used to identify sites of glycosylation on the full-length protein. Of the potential N-glycosylation sites, three located at residues 64, 155, and 169 were occupied, while the two at residues 351 and 356 were not occupied. Threonine 346 was variably O-glycosylated. Thus, full-length selenoprotein P is both N- and O-glycosylated. The shortest isoform of selenoprotein P, which terminates at residue 244, was analyzed for selenide-sulfide and disulfide linkages. In this isoform, a single selenocysteine and seven cysteines are present. Mass spectrometric analysis indicated that a selenide-sulfide bond exists between Sec40 and Cys43. Two disulfides were also detected as Cys149-Cys167 and Cys153-Cys156. The finding of a selenide-sulfide bond in the shortest isoform is compatible with a redox function of this pair that might be analogous to the selenol-thiol pair near the C terminus of animal thioredoxin reductase. The disulfide formed by Cys153-Cys156 also has some characteristics of a redox active pair.

MeSH Terms (19)

Amino Acid Sequence Animals Binding Sites Carbohydrate Sequence Disulfides Glycosylation Molecular Sequence Data Peptide Fragments Peptide Mapping Protein Isoforms Proteins Rats Selenium Selenocysteine Selenoprotein P Selenoproteins Spectrometry, Mass, Electrospray Ionization Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization Sulfides

Connections (2)

This publication is referenced by other Labnodes entities: