ITM1 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. 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. Belongs to the STT3 family. 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). 2 alternatively spliced human isoforms have been reported. Note: This description may include information from UniProtKB.
Protein type: EC; Endoplasmic reticulum; Membrane protein, integral; Membrane protein, multi-pass; Transferase
Chromosomal Location of human Ortholog: 11q24.2
Cellular Component:  endoplasmic reticulum membrane; oligosaccharyltransferase complex; oligosaccharyltransferase III complex
Molecular Function:  dolichyl-diphosphooligosaccharide-protein glycotransferase activity; metal ion binding; protein binding
Biological Process:  co-translational protein modification; post-translational protein modification; protein N-linked glycosylation; protein N-linked glycosylation via asparagine
Disease: Congenital Disorder Of Glycosylation, Type Iw; Congenital Disorder Of Glycosylation, Type Iw, Autosomal Dominant
Reference #:  P46977 (UniProtKB)
Alt. Names/Synonyms: B5; dolichyl-diphosphooligosaccharide protein glycotransferase; Dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit STT3A; FLJ27038; Integral membrane protein 1; integral transmembrane protein 1; ITM1; MGC9042; Oligosaccharyl transferase subunit STT3A; STT3 oligosaccharyltransferase complex catalytic subunit A; STT3, subunit of the oligosaccharyltransferase complex, homolog A; STT3, subunit of the oligosaccharyltransferase complex, homolog A (S. cerevisiae); STT3-A; STT3A; STT3A, catalytic subunit of the oligosaccharyltransferase complex; STT3A, cataylic subunit of the oligosaccharyltransferase complex; STT3A, subunit of the oligosaccharyltransferase complex (catalytic); TMC; transmembrane conserved; Transmembrane protein TMC
Gene Symbols: STT3A
Molecular weight: 80,530 Da
Basal Isoelectric point: 8.28  Predict pI for various phosphorylation states
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Protein Structure Not Found.

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