ricin B-type lectin domain, beta-trefoil fold, found in Drosophila melanogaster polypeptide N-acetylgalactosaminyltransferase 3 (Pgant3) and similar proteins
Pgant3, also called pp-GaNTase 3, protein-UDP acetylgalactosaminyltransferase 3, or UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 3, 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. Pgant3 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 EA2 as a substrate and has weak activity toward Muc5AC-3, -13 and -3/13 substrates. Pgant3 plays a critical role in the regulation of integrin-mediated cell adhesion during wing development by influencing, via glycosylation, the secretion and localization of the integrin ligand Tig to the basal cell layer interface. It may have a role in protein O-glycosylation in the Golgi and thereby in establishing and/or maintaining a proper secretory apparatus structure. Together with Pgant35A, Pgant3 regulates integrin levels and activity-dependent integrin signaling at the synapse in neurons and muscles. 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.
Jiyao W et al.(2023). "The conserved domain database in 2023.",