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  • The EMBO Journal (2009) 28, 2650 - 2661
  • doi:10.1038/emboj.2009.203

Published online: 23 July 2009

Distinct donor and acceptor specificities of Trypanosoma brucei oligosaccharyltransferasesEMBO Open

Luis Izquierdo1,†, Benjamin L Schulz2,†, João A Rodrigues1,‡, Maria Lucia S Güther1, James B Procter1, Geoffrey J Barton1, Markus Aebi2 and Michael A J Ferguson1

  1. Division of Biological Chemistry and Drug Discovery, The College of Life Sciences, University of Dundee, Dundee, UK
  2. Department of Biology, Institute of Microbiology, Eidgenössische Technische Hochschule (ETH) Zurich, Zurich, Switzerland

Correspondence to:

Markus Aebi, Department of Biology, Institute of Microbiology, Eidgenössische Technische Hochschule (ETH) Zurich, 8093 Zurich, Switzerland. Tel.: +41 44 632 64 13; Fax: +41 44 632 11 48; E-mail: aebi@micro.biol.ethz.ch

Michael A J Ferguson, Division of Biological Chemistry and Drug Discovery, The College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK. Tel.: +44 1382 384219; Fax: +44 1382 322558; E-mail: m.a.j.ferguson@dundee.ac.uk

†These authors contributed equally to this work

‡Present address: Centro de Malaria e Doenças Tropicais-Laboratorio Associado, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira, 96, 1349-008 Lisboa, Portugal

Received 30 March 2009; Accepted 18 June 2009

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 Deltastt3 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 Man5GlcNAc2 to specific glycosylation sites whereas TbSTT3B selectively transfers triantennary Man9GlcNAc2 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.

  • Keywords:

    • glycosylation,
    • oligosaccharyltransferase,
    • STT3,
    • Trypanosoma

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The EMBO Journal is published by Nature Publishing Group on behalf of European Molecular Biology Organization