A necessary and sufficient determinant for protein-selective glycosylation in vivo

J Biol Chem. 2008 Jan 25;283(4):1985-91. doi: 10.1074/jbc.M708160200. Epub 2007 Nov 29.

Abstract

A limited number of glycoproteins including luteinizing hormone and carbonic anhydrase-VI (CA6) bear N-linked oligosaccharides that are modified with beta1,4-linked N-acetylgalactosamine (GalNAc). The selective addition of GalNAc to these glycoproteins requires that the beta1,4-N-acetylgalactosaminyltransferase (betaGT) recognize both the oligosaccharide acceptor and a peptide recognition determinant on the substrate glycoprotein. We report here that two recently cloned betaGTs, betaGT3 and betaGT4, that are able to transfer GalNAc to GlcNAc in beta1,4-linkage display the necessary glycoprotein specificity in vivo. Both betaGTs transfer GalNAc to N-linked oligosaccharides on the luteinizing hormone alpha subunit and CA6 but not to those on transferrin (Trf). A single peptide recognition determinant encoded in the carboxyl-terminal 19-amino acid sequence of bovine CA6 mediates transfer of GalNAc to each of its two N-linked oligosaccharides. The addition of this 19-amino acid sequence to the carboxyl terminus of Trf confers full acceptor activity onto Trf for both betaGT3 and betaGT4 in vivo. The complete 19-amino acid sequence is required for optimal GalNAc addition in vivo, indicating that the peptide sequence is both necessary and sufficient for recognition by betaGT3 and betaGT4.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acetylglucosamine / genetics
  • Acetylglucosamine / metabolism*
  • Carbonic Anhydrases / genetics
  • Carbonic Anhydrases / metabolism*
  • Cell Line
  • Glycoproteins / genetics
  • Glycoproteins / metabolism
  • Glycosylation
  • Humans
  • Luteinizing Hormone / genetics
  • Luteinizing Hormone / metabolism*
  • N-Acetylgalactosaminyltransferases / genetics
  • N-Acetylgalactosaminyltransferases / metabolism*
  • Oligosaccharides / genetics
  • Oligosaccharides / metabolism
  • Peptides / genetics
  • Peptides / metabolism
  • Protein Modification, Translational / physiology*
  • Substrate Specificity / physiology
  • Transferrin / genetics
  • Transferrin / metabolism

Substances

  • Glycoproteins
  • Oligosaccharides
  • Peptides
  • Transferrin
  • Luteinizing Hormone
  • B4GALNT3 protein, human
  • B4GALNT4 protein, human
  • N-Acetylgalactosaminyltransferases
  • Carbonic Anhydrases
  • carbonic anhydrase VI
  • Acetylglucosamine