Glycopeptide N-acetylgalactosaminyltransferase specificities for O-glycosylated sites on MUC5AC mucin motif peptides.
The recombinant proteins of the two novel UDP-N-acetylgalactosamine (GalNAc) glycopeptide:N-acetylgalactosaminyltransferases (designated gpGaNTase-T7 and gpGaNTase-T9) were assayed with O-glycosylated products obtained from the prior action of the ubiquitous transferases (GaNTase-T1 and GaNTase-T2) towards MUC5AC mucin motif peptides (GTTPSPVPTTSTTSAP and peptides with single amino acid substitutions, GTTPSAVPTTSTTSVP and GTTPSPVPTTSITSVP, that are a reflection of mucin molecule polymorphism). gpGaNTase-T9 is known to be expressed differentially and more abundantly than gpGaNTase-T7 in some tissues; the results of in vitro glycosylation also indicates a difference in acceptor substrate specificities between the gpGaNTase isoforms. With the use of capillary electrophoresis, MS and Edman degradation, our study suggests that, in the O-glycosylation of mucin-type proteins, approach and recognition signalling by gpGaNTase-T7 and gpGaNTase-T9 depend largely on the peptide's primary structure (for example the presence of multiple clusters of hydroxy amino acids and the number of GalNAc residues attached to the peptide backbone). O-glycosylation in terms of sites of attachment seems to be less random than previously described and, if sequential reactions are ordered throughout the Golgi stack, the complete O-glycosylation of the mucin molecules seems to be finely tuned to respond to specific damage to, or attack on, epithelia.
Tetaert
D
D
Unité INSERM No. 377, Biologie et Physiopathologie de Cellules Mucipares, Place de Verdun, 59045 Lille Cédex, France. tetaert@lille.inserm.fr
Ten Hagen
K G
KG
Richet
C
C
Boersma
A
A
Gagnon
J
J
Degand
P
P
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D006031:Glycosylation; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D055271:Mucin 5AC; D009077:Mucins / Q000737:chemistry* / Q000378:metabolism*; D017350:N-Acetylgalactosaminyltransferases / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013379:Substrate Specificity; D014162:Transfection
D007527:Isoenzymes; D055271:Mucin 5AC; D009077:Mucins; D010446:Peptide Fragments; D010455:Peptides; D011994:Recombinant Proteins; D017350:N-Acetylgalactosaminyltransferases