ricin B-type lectin domain, beta-trefoil fold, found in Drosophila melanogaster polypeptide N-acetylgalactosaminyltransferase 1 (Pgant1) and similar proteins
Pgant1, also called pp-GaNTase 1, protein-UDP acetylgalactosaminyltransferase 1, or UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 1, functions as a GalNAc transferase (EC 2.4.1.41) that catalyzes 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. Pgant1 can both act as a peptide transferase that transfers GalNAc onto unmodified peptide substrates, and as a glycopeptide transferase that requires the prior addition of a GalNAc on a peptide before adding additional GalNAc moieties. It prefers the monoglycosylated Muc5AC-3 as a substrate. Members of this subfamily contain a ricin B-type lectin domain at the C-terminus. The ricin B-type lectin domain shows a beta-trefoil fold, which is characterized by 12 beta strands folded into three similar trefoil subdomains (alpha, beta, and gamma) associated to give an overall structure with pseudo-3-fold symmetry. Each subdomain bears a potential sugar binding site.
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