<p dir="ltr">Ubiquitination and ADP-ribosylation are reversible post-translational modifications involved in various cellular activities. Pathogens like <i>Legionella pneumophila</i> and <i>Chromobacterium violaceum</i> target host ubiquitin system via modifications involving ADP-ribosylation. Specifically, <i>Legionella pneumophila</i> mediates atypical ubiquitination of host targets using the SidE effector family in a process that involves ubiquitin ADP-ribosylation on arginine 42 as an obligatory step. On the other hand, <i>Chromobacterium violaceum</i> effector CteC ADP-ribosylates threonine 66 of ubiquitin and causes overall blocking of host ubiquitin signaling. Removal of ADP-ribosylation requires (ADP-ribosyl)hydrolases, with macrodomain enzymes being a major family in this category. In the current study, a proteome-wide screening of ubiquitin interactors in the <i>Legionella</i> secreted proteome was performed, which led to the <i>Legionella</i> macrodomain effector MavL as a regulator of the SidE-mediated ubiquitination pathway by reversing the ubiquitin arginine ADP-ribosylation, likely to minimize potential detrimental effects caused by modified ubiquitin. Crystal structure of ADP-ribose-bound MavL was determined, providing structural insights into substrate recognition and catalytic mechanism. Further bioinformatical analyses reveal DUF4804 as a class of MavL-like macrodomain enzymes uniquely selective for mono-ADP-ribosylated arginine residue. The arginine-specific macrodomains are also present in eukaryotes, as exemplified by two previously uncharacterized (ADP-ribosyl)hydrolases in <i>Drosophila melanogaster</i>. Crystal structures of several proteins in this class provide insights into arginine specificity and a shared mode of ADP-ribose interaction distinct from previously characterized macrodomains. The crystal structure of NAD<sup>+</sup>-bound CteC was also determined, which provided insights into its ADP-ribosylation activity and its ubiquitin specificity. Collectively, the studies described here provide biochemical and structural characterizations and mechanistic insights into bacterial effectors associated with ubiquitin ADP-ribosylation.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/24232969 |
| Date | 02 October 2023 |
| Creators | Zhengrui Zhang (17081689) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/BIOCHEMICAL_AND_STRUCTURAL_STUDIES_OF_PATHOGEN_EFFECTORS_ASSOCIATED_WITH_UBIQUITIN_ADP-RIBOSYLATION/24232969 |
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