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Exploitation of the host cell lipidation machinery by the Legionella pneumophilla U-box E3 ligase GobX

Wednesday, September 24, 2014 — Poster Session IV

10:00 a.m. –12:00 p.m.

FAES Academic Center



* FARE Award Winner


  • Y. Lin
  • T.R. Evans
  • M.P. Machner


Legionella pneumophila, the causative agent of Legionnaire’s disease, represents an ideal model organism to study bacterial effector proteins. L. pneumophila translocates over 300 effector proteins into host cells during infection. Most effector proteins have no known functions due to lack of primary sequence homology. We used a bioinformatics approach to search for L. pneumophila effector proteins that contain E3 ubiquitin ligase domains. We identified 15 additional L. pneumophila effectors of unknown function as putative E3 ligases, 6 of which we confirmed experimentally in vitro or in vivo. Among them, GobX contains a U-box E3 ligase domain, and in transiently transfected COS-1 cells, it showed intense localization to the Golgi. The Golgi localization is depending on the region between aa171-190, and biochemical analyses using the metabolic labeling agent 17-ODYA followed by click chemistry revealed that GobX is S-palmitoylated on Cys175. Transfection of HEK293T cells with GobX and 23 mammalian DHHC acyl transferases indicated that GobX is preferentially palmitoylated by DHHC12, 20, 21, 22, and 23. Our study shows that E3 ligases are more abundant in bacterial pathogens than predicted, and GobX represents the first example of a Legionella pneumophila effector protein that can simultaneously exploit two host machineries, ubiquitination and lipidation.

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