Molecular basis for glycan recognition and reaction priming of eukaryotic oligosaccharyltransferase
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Date
2022-11-26
Publication Type
Journal Article
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Abstract
Oligosaccharyltransferase (OST) is the central enzyme of N-linked protein glycosylation. It catalyzes the transfer of a pre-assembled glycan, GlcNAc2Man9Glc3, 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 (Glc3) 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.
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published
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Journal / series
Volume
13 (1)
Pages / Article No.
7296
Publisher
Nature
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Subject
Cryoelectron microscopy; Enzyme mechanisms; Glycobiology; Polysaccharides
Organisational unit
03652 - Locher, Kaspar / Locher, Kaspar
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Funding
173709 - GlycoSTART: Structure and function of eukaryotic oligosaccharyltransferase (SNF)
196862 - Structural and mechanistic investigations of membrane-integral enzymes involved in eukaryotic protein N-glycosylation pathway (SNF)
196862 - Structural and mechanistic investigations of membrane-integral enzymes involved in eukaryotic protein N-glycosylation pathway (SNF)