Distinct donor and acceptor specificities of Trypanosoma brucei oligosaccharyltransferases

Luis Izquierdo, Benjamin L. Schulz, Joao A. Rodrigues, Maria Lucia S. Guther, James B. Procter, Geoffrey J. Barton, Markus Aebi (Lead / Corresponding author), Michael A. J. Ferguson (Lead / Corresponding author)

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    Abstract

    Asparagine-linked glycosylation is catalysed by oligosaccharyltransferase (OTase). In Trypanosoma brucei OTase activity is catalysed by single-subunit enzymes encoded by three paralogous genes of which TbSTT3B and TbSTT3C can complement a yeast Delta stt3 mutant. The two enzymes have overlapping but distinct peptide acceptor specificities, with TbSTT3C displaying an enhanced ability to glycosylate sites flanked by acidic residues. TbSTT3A and TbSTT3B, but not TbSTT3C, are transcribed in the bloodstream and procyclic life cycle stages of T. brucei. Selective knockdown and analysis of parasite protein N-glycosylation showed that TbSTT3A selectively transfers biantennary Man(5)GlcNAc(2) to specific glycosylation sites whereas TbSTT3B selectively transfers triantennary Man(9)GlcNAc(2) to others. Analysis of T. brucei glycosylation site occupancy showed that TbSTT3A and TbSTT3B glycosylate sites in acidic to neutral and neutral to basic regions of polypeptide, respectively. This embodiment of distinct specificities in single-subunit OTases may have implications for recombinant glycoprotein engineering. TbSTT3A and TbSTT3B could be knocked down individually, but not collectively, in tissue culture. However, both were independently essential for parasite growth in mice, suggesting that inhibiting protein N-glycosylation could have therapeutic potential against trypanosomiasis. The EMBO Journal (2009) 28, 2650-2661. doi: 10.1038/emboj.2009.203; Published online 23 July 2009 Subject Categories: microbiology & pathogens; proteins

    Original languageEnglish
    Pages (from-to)2650-2661
    Number of pages12
    JournalEMBO Journal
    Volume28
    Issue number17
    DOIs
    Publication statusPublished - 2 Sep 2009

    Keywords

    • glycosylation
    • oligosaccharyltransferase
    • STT3
    • Trypanosoma
    • VARIANT SURFACE GLYCOPROTEIN
    • N-GLYCOSYLATION
    • LEISHMANIA-MAJOR
    • AFRICAN TRYPANOSOMES
    • REPETITIVE PROTEIN
    • MEMBRANE ANCHOR
    • LINKED GLYCANS
    • IN-VIVO
    • GENE
    • STT3

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