STT3A Antibody - #DF12757

Catalytic subunit of the oligosaccharyl transferase (OST) complex that catalyzes the initial transfer of a defined glycan (Glc(3)Man(9)GlcNAc(2) in eukaryotes) from the lipid carrier dolichol-pyrophosphate to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains, the first step in protein N-glycosylation. N-glycosylation occurs cotranslationally and the complex associates with the Sec61 complex at the channel-forming translocon complex that mediates protein translocation across the endoplasmic reticulum (ER). All subunits are required for a maximal enzyme activity. This subunit contains the active site and the acceptor peptide and donor lipid-linked oligosaccharide (LLO) binding pockets (By similarity). STT3A is present in the majority of OST complexes and mediates cotranslational N-glycosylation of most sites on target proteins, while STT3B-containing complexes are required for efficient post-translational glycosylation and mediate glycosylation of sites that have been skipped by STT3A.

Endoplasmic reticulum. Endoplasmic reticulum membrane>Multi-pass membrane protein.

Expressed at high levels in placenta, liver, muscle and pancreas, and at very low levels in brain, lung and kidney. Expressed in skin fibroblasts (at protein level).

Despite low primary sequence conservation between eukaryotic catalytic subunits and bacterial and archaeal single subunit OSTs (ssOST), structural comparison revealed several common motifs at spatially equivalent positions, like the DXD motif 1 on the external loop 1 and the DXD motif 2 on the external loop 2 involved in binding of the metal ion cofactor and the carboxamide group of the acceptor asparagine, the conserved Glu residue of the TIXE/SVSE motif on the external loop 5 involved in catalysis, as well as the WWDYG and the DK/MI motifs in the globular domain that define the binding pocket for the +2 Ser/Thr of the acceptor sequon. In bacterial ssOSTs, an Arg residue was found to interact with a negatively charged side chain at the -2 position of the sequon. This Arg is conserved in bacterial enzymes and correlates with an extended sequon requirement (Asp-X-Asn-X-Ser/Thr) for bacterial N-glycosylation.

Belongs to the STT3 family.