STT3A
Description
The STT3A (STT3 oligosaccharyltransferase complex catalytic subunit A) is a protein-coding gene located on chromosome 11.
STT3A, catalytic subunit of the oligosaccharyltransferase complex is a protein that in humans is encoded by the STT3A gene. The protein encoded by this gene is a catalytic subunit of the N-oligosaccharyltransferase (OST) complex, which functions in the endoplasmic reticulum to transfer glycan chains to asparagine residues of target proteins. A separate complex containing a similar catalytic subunit with an overlapping function also exists. Multiple transcript variants encoding different isoforms have been found for this gene.
STT3A is the catalytic subunit of the oligosaccharyltransferase (OST) complex, responsible for the initial transfer of a specific 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. This process, known as protein N-glycosylation, occurs cotranslationally. The OST complex associates with the Sec61 complex, which mediates protein translocation across the endoplasmic reticulum (ER). All subunits of the OST complex are required for optimal enzymatic activity. STT3A contains the active site and binding pockets for both the acceptor peptide and the donor lipid-linked oligosaccharide (LLO). STT3A is the dominant catalytic subunit in most OST complexes and mediates cotranslational N-glycosylation of the majority of sites on target proteins. In contrast, STT3B-containing complexes are necessary for efficient post-translational glycosylation, particularly for sites that were missed by STT3A.
STT3A is also known as CDG1WAD, CDG1WAR, ITM1, STT3-A, TMC.
Associated Diseases
- Congenital disorder of glycosylation, type Iw
- STT3A-CDG
- Congenital disorder of glycosylation, type Iw, autosomal dominant
