Protein O-Mannosyltransferases Associate with the Translocon to Modify Translocating Polypeptide Chains
O-Mannosylation and N-glycosylation are essential protein modifications that are initiated in the endoplasmic reticulum (ER). Protein translocation across the ER membrane and N-glycosylation are highly coordinated processes that take place at the translocon-oligosaccharyltransferase (OST) complex. I...
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| Main Authors: | , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
February 11, 2014
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| In: |
The journal of biological chemistry
Year: 2014, Volume: 289, Issue: 12, Pages: 8599-8611 |
| ISSN: | 1083-351X |
| DOI: | 10.1074/jbc.M113.543116 |
| Online Access: | Verlag, kostenfrei, Volltext: http://dx.doi.org/10.1074/jbc.M113.543116 Verlag, kostenfrei, Volltext: http://www.jbc.org/content/289/12/8599 
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| Author Notes: | Martin Loibl, Lina Wunderle, Johannes Hutzler, Benjamin L. Schulz, Markus Aebi, Sabine Strahl |
| Summary: | O-Mannosylation and N-glycosylation are essential protein modifications that are initiated in the endoplasmic reticulum (ER). Protein translocation across the ER membrane and N-glycosylation are highly coordinated processes that take place at the translocon-oligosaccharyltransferase (OST) complex. In analogy, it was assumed that protein O-mannosyltransferases (PMTs) also act at the translocon, however, in recent years it turned out that prolonged ER residence allows O-mannosylation of un-/misfolded proteins or slow folding intermediates by Pmt1-Pmt2 complexes. Here, we reinvestigate protein O-mannosylation in the context of protein translocation. We demonstrate the association of Pmt1-Pmt2 with the OST, the trimeric Sec61, and the tetrameric Sec63 complex in vivo by co-immunoprecipitation. The coordinated interplay between PMTs and OST in vivo is further shown by a comprehensive mass spectrometry-based analysis of N-glycosylation site occupancy in pmtΔ mutants. In addition, we established a microsomal translation/translocation/O-mannosylation system. Using the serine/threonine-rich cell wall protein Ccw5 as a model, we show that PMTs efficiently mannosylate proteins during their translocation into microsomes. This in vitro system will help to unravel mechanistic differences between co- and post-translocational O-mannosylation. |
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| Item Description: | Gesehen am 16.05.2017 |
| Physical Description: | Online Resource |
| ISSN: | 1083-351X |
| DOI: | 10.1074/jbc.M113.543116 |