STT3 oligosaccharyltransferase complex catalytic subunit A (STT3A)

STT3 oligosaccharyltransferase complex catalytic subunit A (STT3A) is the **catalytic subunit** of the oligosaccharyltransferase (OST) complex, a multi-protein enzyme complex located in the **endoplasmic reticulum**. STT3A catalyzes the **transfer of preassembled glycans from a dolichol-pyrophosphate lipid carrier to asparagine residues** within the Asn-X-Ser/Thr consensus sequon of nascent polypeptides, performing **cotranslational N-glycosylation**—the initial and essential step of protein N-linked glycosylation in eukaryotes[1][2][5]. The STT3A-containing OST complex is functionally distinct from the STT3B-containing isoform: STT3A primarily mediates cotranslational glycosylation, while STT3B is required for efficient post-translational modification of glycosylation sites missed by STT3A[1][6]. Mutations in STT3A lead to human disease, specifically congenital disorders of glycosylation, characterized by defective N-linked protein glycosylation and a broad range of clinical symptoms[6]. STT3A complexes are evolutionarily conserved and are required for normal protein folding and quality control, as improper glycosylation can result in misfolded proteins and endoplasmic reticulum stress[1][3][6].

Other names

Dolichyl-diphosphooligosaccharide–protein glycosyltransferase subunit STT3AITM1TMCOligosaccharyltransferase subunit STT3AB5Integral membrane protein 1Transmembrane protein TMCMGC9042CDG1WADCDG1WAR