FunctionCatalyzes the initial reaction in O-linked oligosaccharide biosynthesis, the transfer of an N-acetyl-D-galactosamine residue to a serine or threonine residue on the protein receptor. Has a broad spectrum of substrates for peptides such as EA2, Muc5AC, Muc1a, Muc1b. Probably involved in O-linked glycosylation of the immunoglobulin A1 (IgA1) hinge region.
Tissue specificityWidely expressed.
PathwayProtein modification; protein glycosylation.
Sequence similaritiesBelongs to the glycosyltransferase 2 family. GalNAc-T subfamily. Contains 1 ricin B-type lectin domain.
DomainThere are two conserved domains in the glycosyltransferase region: the N-terminal domain (domain A, also called GT1 motif), which is probably involved in manganese coordination and substrate binding and the C-terminal domain (domain B, also called Gal/GalNAc-T motif), which is probably involved in catalytic reaction and UDP-Gal binding. The ricin B-type lectin domain binds to GalNAc and contributes to the glycopeptide specificity.
Cellular localizationGolgi apparatus > Golgi stack membrane. Secreted. Resides preferentially in the trans and medial parts of the Golgi stack. A secreted form also exists.