6ftj | pdb_00006ftj
Cryo-EM Structure of the Mammalian Oligosaccharyltransferase Bound to Sec61 and the Non-programmed 80S Ribosome
Structural highlights
Function[STT3A_CANLF] Catalytic 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. 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). SST3A seems to be involved in complex substrate specificity. STT3A is present in the majority of OST complexes and mediates cotranslational N-glycosylation of most sites on target proteins, while STT3B-containing complexes are required for efficient post-translational glycosylation and mediate glycosylation of sites that have been skipped by STT3A.[UniProtKB:P46977][1] [U3KPD5_RABIT] Binds to the 23S rRNA.[RuleBase:RU000576] [OSTC_CANLF] May act as substrate-specific component 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. May be involved in N-glycosylation of APP (amyloid-beta precursor protein). Can modulate gamma-secretase cleavage of APP by enhancing endoprotelysis of PSEN1.[UniProtKB:Q9NRP0] [RPN1_CANLF] 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.[2] Publication Abstract from PubMedProtein synthesis, transport and N-glycosylation are coupled at the mammalian endoplasmic reticulum (ER) by complex formation between the ribosome, the Sec61 protein-conducting channel and the oligosaccharyltransferase (OST). Here, we used different cryo-electron microscopy approaches to determine structures of native and solubilized ribosome-Sec61-OST complexes. A molecular model for the catalytic OST subunit revealed how STT3A is integrated into the OST and how STT3 paralog specificity for translocon-associated OST is achieved. The OST subunit DC2 was placed at the interface between Sec61 and STT3A, where it acts as a versatile module for recruitment of STT3A-containing OST to the ribosome-Sec61 complex. This detailed structural view on the molecular architecture of the co-translational machinery for N-glycosylation provides the basis for a mechanistic understanding of glycoprotein biogenesis at the ER. Structural basis for coupling protein transport and N-glycosylation at the mammalian endoplasmic reticulum.,Braunger K, Pfeffer S, Shrimal S, Gilmore R, Berninghausen O, Mandon EC, Becker T, Forster F, Beckmann R Science. 2018 Mar 8. pii: science.aar7899. doi: 10.1126/science.aar7899. PMID:29519914[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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