6S7O

Cryo-EM structure of human oligosaccharyltransferase complex OST-A

Summary for 6S7O

• Entry DOI: 10.2210/pdb6s7o/pdb
• EMDB information: 10110
• Descriptor: Dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit STT3A, alpha-D-mannopyranose-(1-2)-alpha-D-mannopyranose-(1-2)-alpha-D-mannopyranose-(1-3)-[alpha-D-mannopyranose-(1-6)-alpha-D-mannopyranose-(1-6)]beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, alpha-D-mannopyranose-(1-2)-alpha-D-mannopyranose-(1-3)-[alpha-D-mannopyranose-(1-3)-[alpha-D-mannopyranose-(1-6)]alpha-D-mannopyranose-(1-6)]beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, ... (15 entities in total)
• Functional Keywords: n-glycosylation, oligosaccharyltransferase, osta, transferase
• Biological source: Homo sapiens (Human); More
• Total number of polymer chains: 8
• Total formula weight: 325886.44

Authors

Ramirez, A.S.,Kowal, J.,Locher, K.P. (deposition date: 2019-07-05, release date: 2019-12-18, Last modification date: 2024-11-06)

Primary citation

Ramirez, A.S.,Kowal, J.,Locher, K.P.
Cryo-electron microscopy structures of human oligosaccharyltransferase complexes OST-A and OST-B.
Science, 366:1372-1375, 2019

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 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.

PubMed: 31831667
DOI: 10.1126/science.aaz3505

Experimental method

ELECTRON MICROSCOPY (3.5 Å)