Molecular basis for glycan recognition and reaction priming of eukaryotic oligosaccharyltransferase

Oligosaccharyltransferase (OST) is the central enzyme of N -linked protein glycosylation. It catalyzes the transfer of a pre-assembled glycan, GlcNAc 2 Man 9 Glc 3 , from a dolichyl-pyrophosphate donor to acceptor sites in secretory proteins in the lumen of the endoplasmic reticulum. Precise recogni...

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Bibliographic Details
Published in:Nature communications 2022-11, Vol.13 (1), p.7296-7296, Article 7296
Main Authors: Ramírez, Ana S., de Capitani, Mario, Pesciullesi, Giorgio, Kowal, Julia, Bloch, Joël S., Irobalieva, Rossitza N., Reymond, Jean-Louis, Aebi, Markus, Locher, Kaspar P.
Format: Article
Language:English
Subjects:
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Binding
Biosynthesis
Catalysis
Catalytic subunits
Endoplasmic reticulum
Enzymes
Eukaryotic Cells
Glycan
Glycoproteins
Glycosylation
Hexosyltransferases
Humanities and Social Sciences
Humans
Male
multidisciplinary
Oligosaccharyltransferase
Polysaccharides
Priming
Proteins
Quality control
Recognition
Saccharomyces cerevisiae
Science
Science (multidisciplinary)
Substrates
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Summary:Oligosaccharyltransferase (OST) is the central enzyme of N -linked protein glycosylation. It catalyzes the transfer of a pre-assembled glycan, GlcNAc 2 Man 9 Glc 3 , from a dolichyl-pyrophosphate donor to acceptor sites in secretory proteins in the lumen of the endoplasmic reticulum. Precise recognition of the fully assembled glycan by OST is essential for the subsequent quality control steps of glycoprotein biosynthesis. However, the molecular basis of the OST-donor glycan interaction is unknown. Here we present cryo-EM structures of S. cerevisiae OST in distinct functional states. Our findings reveal that the terminal glucoses (Glc 3 ) of a chemo-enzymatically generated donor glycan analog bind to a pocket formed by the non-catalytic subunits WBP1 and OST2. We further find that binding either donor or acceptor substrate leads to distinct primed states of OST, where subsequent binding of the other substrate triggers conformational changes required for catalysis. This alternate priming allows OST to efficiently process closely spaced N -glycosylation sites. Oligosaccharyltransferase (OST), the central enzyme in N-glycosylation, modifies acceptor proteins by attaching a complex glycan. Cryo-EM structures of OST in distinct states, reveal the molecular basis of substrate recognition and catalysis.
ISSN:2041-1723
2041-1723
DOI:10.1038/s41467-022-35067-x