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Title | Cryo-electron microscopy structures of human oligosaccharyltransferase complexes OST-A and OST-B. |
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Journal, issue, pages | Science, Vol. 366, Issue 6471, Page 1372-1375, Year 2019 |
Publish date | Dec 13, 2019 |
Authors | Ana S Ramírez / Julia Kowal / Kaspar P Locher / |
PubMed Abstract | Oligosaccharyltransferase (OST) catalyzes the transfer of a high-mannose glycan onto secretory proteins in the endoplasmic reticulum. Mammals express two distinct OST complexes that act in a ...Oligosaccharyltransferase (OST) catalyzes the transfer of a high-mannose glycan onto secretory proteins in the endoplasmic reticulum. Mammals express two distinct OST complexes that act in a cotranslational (OST-A) or posttranslocational (OST-B) manner. Here, we present high-resolution cryo-electron microscopy structures of human OST-A and OST-B. Although they have similar overall architectures, structural differences in the catalytic subunits STT3A and STT3B facilitate contacts to distinct OST subunits, DC2 in OST-A and MAGT1 in OST-B. In OST-A, interactions with TMEM258 and STT3A allow ribophorin-I to form a four-helix bundle that can bind to a translating ribosome, whereas the equivalent region is disordered in OST-B. We observed an acceptor peptide and dolichylphosphate bound to STT3B, but only dolichylphosphate in STT3A, suggesting distinct affinities of the two OST complexes for protein substrates. |
External links | Science / PubMed:31831667 |
Methods | EM (single particle) |
Resolution | 3.5 Å |
Structure data | EMDB-10110, PDB-6s7o: EMDB-10112, PDB-6s7t: |
Chemicals | ChemComp-KZB: ChemComp-EGY: ChemComp-MG: ChemComp-KZE: ChemComp-0K3: |
Source |
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Keywords | TRANSFERASE / N-glycosylation / Oligosaccharyltransferase / OSTA / OSTB |