6p25
Structure of S. cerevisiae protein O-mannosyltransferase Pmt1-Pmt2 complex bound to the sugar donor and a peptide acceptor
Structural highlights
FunctionPMT1_YEAST Protein O-mannosyltransferase involved in O-glycosylation which is essential for cell wall rigidity. Forms a heterodimeric complex with PMT2 and more rarely with PMT3 to transfer mannose from Dol-P-mannose to Ser or Thr residues on proteins. The PMT1-PMT2 complex participates in oxidative protein folding, ER-associated protein degradation (ERAD), as well as ER export. Required for incorporation of proteins in the cell wall.[1] [2] [3] [4] [5] Publication Abstract from PubMedIn eukaryotes, a nascent peptide entering the endoplasmic reticulum (ER) is scanned by two Sec61 translocon-associated large membrane machines for protein N-glycosylation and protein O-mannosylation, respectively. While the structure of the eight-protein oligosaccharyltransferase complex has been determined recently, the structures of mannosyltransferases of the PMT family, which are an integral part of ER protein homeostasis, are still unknown. Here we report cryo-EM structures of the Saccharomyces cerevisiae Pmt1-Pmt2 complex bound to a donor and an acceptor peptide at 3.2-A resolution, showing that each subunit contains 11 transmembrane helices and a lumenal beta-trefoil fold termed the MIR domain. The structures reveal the substrate recognition model and confirm an inverting mannosyl-transferring reaction mechanism by the enzyme complex. Furthermore, we found that the transmembrane domains of Pmt1 and Pmt2 share a structural fold with the catalytic subunits of oligosaccharyltransferases, confirming a previously proposed evolutionary relationship between protein O-mannosylation and protein N-glycosylation. Structure of the eukaryotic protein O-mannosyltransferase Pmt1-Pmt2 complex.,Bai L, Kovach A, You Q, Kenny A, Li H Nat Struct Mol Biol. 2019 Jul 8. pii: 10.1038/s41594-019-0262-6. doi:, 10.1038/s41594-019-0262-6. PMID:31285605[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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