Cryo-electron microscopy structures of human oligosaccharyltransferase complexes OST-A and OST-B.Ramirez, A.S., Kowal, J., Locher, K.P.
(2019) Science 366: 1372-1375
- PubMed: 31831667
- DOI: https://doi.org/10.1126/science.aaz3505
- Primary Citation of Related Structures:
- 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.
Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH), CH-8093 Zürich, Switzerland. firstname.lastname@example.org.