TY - JOUR
T1 - The lectin domain of UDP-N-acetyl-D-galactosamine
T2 - Polypeptide N-acetylgalactosaminyltransferase-T4 directs its glycopeptide specificities
AU - Hassan, Helle
AU - Reis, Celso A.
AU - Bennett, Eric Paul
AU - Mirgorodskaya, Ekaterina
AU - Roepstorff, Peter
AU - Hollingsworth, Michael A.
AU - Burchell, Joy
AU - Taylor-Papadimitriou, Joyce
AU - Clausen, Henrik
PY - 2000/12/8
Y1 - 2000/12/8
N2 - The initiation step of mucin-type O-glycosylation is controlled by a large family of homologous UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (GalNAc-transferases). Differences in kinetic properties, substrate specificities, and expression patterns of these isoenzymes provide for differential regulation of O-glycan attachment sites and density. Recently, it has emerged that some GalNAc-transferase isoforms in vitro selectively function with partially GalNAc O-glycosylated acceptor peptides rather than with the corresponding unglycosylated peptides. O-Glycan attachment to selected sites, most notably two sites in the MUC1 tandem repeat, is entirely dependent on the glycosylation-dependent function of GalNAc-T4. Here we present data that a putative lectin domain found in the C terminus of GalNAc-T4 functions as a GalNAc lectin and confers its glycopeptide specificity. A single amino acid substitution in the lectin domain of a secreted form of GalNAc-T4 selectively blocked GalNAc-glycopeptide activity, while the general activity to peptides exerted by this enzyme was unaffected. Furthermore, the GalNAc-glycopeptide activity of wild-type secreted GalNAc-T4 was selectively inhibited by free GalNAc, while the activity with peptides was unaffected.
AB - The initiation step of mucin-type O-glycosylation is controlled by a large family of homologous UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (GalNAc-transferases). Differences in kinetic properties, substrate specificities, and expression patterns of these isoenzymes provide for differential regulation of O-glycan attachment sites and density. Recently, it has emerged that some GalNAc-transferase isoforms in vitro selectively function with partially GalNAc O-glycosylated acceptor peptides rather than with the corresponding unglycosylated peptides. O-Glycan attachment to selected sites, most notably two sites in the MUC1 tandem repeat, is entirely dependent on the glycosylation-dependent function of GalNAc-T4. Here we present data that a putative lectin domain found in the C terminus of GalNAc-T4 functions as a GalNAc lectin and confers its glycopeptide specificity. A single amino acid substitution in the lectin domain of a secreted form of GalNAc-T4 selectively blocked GalNAc-glycopeptide activity, while the general activity to peptides exerted by this enzyme was unaffected. Furthermore, the GalNAc-glycopeptide activity of wild-type secreted GalNAc-T4 was selectively inhibited by free GalNAc, while the activity with peptides was unaffected.
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U2 - 10.1074/jbc.M005783200
DO - 10.1074/jbc.M005783200
M3 - Article
C2 - 10984485
AN - SCOPUS:0034624056
VL - 275
SP - 38197
EP - 38205
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 49
ER -