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Ubiquitination independent of E1 and E2 enzymes by bacterial effectors

Nature volume 533, pages 120124 (05 May 2016) | Download Citation

This article has been updated


Signalling by ubiquitination regulates virtually every cellular process in eukaryotes. Covalent attachment of ubiquitin to a substrate is catalysed by the E1, E2 and E3 three-enzyme cascade1, which links the carboxy terminus of ubiquitin to the ε-amino group of, in most cases, a lysine of the substrate via an isopeptide bond. Given the essential roles of ubiquitination in the regulation of the immune system, it is not surprising that the ubiquitination network is a common target for diverse infectious agents2. For example, many bacterial pathogens exploit ubiquitin signalling using virulence factors that function as E3 ligases, deubiquitinases3 or as enzymes that directly attack ubiquitin4. The bacterial pathogen Legionella pneumophila utilizes approximately 300 effectors that modulate diverse host processes to create a permissive niche for its replication in phagocytes5. Here we demonstrate that members of the SidE effector family of L. pneumophila ubiquitinate multiple Rab small GTPases associated with the endoplasmic reticulum. Moreover, we show that these proteins are capable of catalysing ubiquitination without the need for the E1 and E2 enzymes. A putative mono-ADP-ribosyltransferase motif critical for the ubiquitination activity is also essential for the role of the SidE family in intracellular bacterial replication in a protozoan host. The E1/E2-independent ubiquitination catalysed by these enzymes is energized by nicotinamide adenine dinucleotide, which activates ubiquitin by the formation of ADP-ribosylated ubiquitin. These results establish that ubiquitination can be catalysed by a single enzyme, the activity of which does not require ATP.

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  • 04 May 2016

    Details for ref. 28 were updated.


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We thank P. Hollenbeck (Purdue University) for critical reading of the manuscript. J. Barbieri (Medical College of Wisconsin) for plasmids. This work was supported by National Institutes of Health grants R56AI103168, K02AI085403 and R21AI105714 (Z.-Q.L.), 2R01GM103401 (C.D.) and National Natural Science Foundation of China grants 21305006 and 21475005 (X.L.).

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Author notes

    • Yunhao Tan

    Present address: Division of Gastroenterology, Boston Children’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.


  1. Purdue Institute for Inflammation, Immunology and Infectious Disease and Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA

    • Jiazhang Qiu
    • , Yunhao Tan
    •  & Zhao-Qing Luo
  2. Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA

    • Michael J. Sheedlo
    •  & Chittaranjan Das
  3. Institute of Analytical Chemistry and Synthetic and Functional Biomolecules Center, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China

    • Kaiwen Yu
    •  & Xiaoyun Liu
  4. Biological Science Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA

    • Ernesto S. Nakayasu


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J.Q. and Z.-Q.L. conceived the general ideas for this work. J.Q. and Z.-Q.L. planned, performed and interpreted experiments. Y.T. initiated the project, performed the bioinformatics analysis and determined the importance of the predicted mART motif in yeast toxicity. M.S., E.S.N., J.Q. and C.D. determined the reaction intermediates. K.Y., X.L. and E.S.N. performed mass spectrometric analyses. J.Q. and Z.-Q.L. wrote the manuscript and all authors provided editorial input.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Zhao-Qing Luo.

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