3ga4 | pdb_00003ga4
Crystal structure of Ost6L (photoreduced form)
Structural highlights
Function[OST6_YEAST] Essential subunit of the N-oligosaccharyl transferase (OST) complex which catalyzes the transfer of a high mannose oligosaccharide from a lipid-linked oligosaccharide donor to an asparagine residue within an Asn-X-Ser/Thr consensus motif in nascent polypeptide chains. Can participate in redox reactions and is able to catalyze dithiol-disulfide exchange reactions with other proteins, albeit with relatively low efficiency. May form transient disulfide bonds with nascent polypeptides in the endoplasmic reticulum and thereby promote efficient glycosylation. N-glycosylation occurs cotranslationally and the complex associates with the Sec61 complex at the channel-forming translocon complex that mediates protein translocation across the endoplasmic reticulum (ER). All subunits are required for a maximal oligosaccharyl transferase activity.[1] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedAsparagine-linked glycosylation is a common posttranslational modification of diverse secretory and membrane proteins in eukaryotes, where it is catalyzed by the multiprotein complex oligosaccharyltransferase. The functions of the protein subunits of oligoasccharyltransferase, apart from the catalytic Stt3p, are ill defined. Here we describe functional and structural investigations of the Ost3/6p components of the yeast enzyme. Genetic, biochemical and structural analyses of the lumenal domain of Ost6p revealed oxidoreductase activity mediated by a thioredoxin-like fold with a distinctive active-site loop that changed conformation with redox state. We found that mutation of the active-site cysteine residues of Ost6p and its paralogue Ost3p affected the glycosylation efficiency of a subset of glycosylation sites. Our results show that eukaryotic oligosaccharyltransferase is a multifunctional enzyme that acts at the crossroads of protein modification and protein folding. Oxidoreductase activity of oligosaccharyltransferase subunits Ost3p and Ost6p defines site-specific glycosylation efficiency.,Schulz BL, Stirnimann CU, Grimshaw JP, Brozzo MS, Fritsch F, Mohorko E, Capitani G, Glockshuber R, Grutter MG, Aebi M Proc Natl Acad Sci U S A. 2009 Jul 7;106(27):11061-6. Epub 2009 Jun 23. PMID:19549845[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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