Structural Basis Of Ubiquitin Modification By Sdea From Legionella Pneumophila

Protein ubiquitination is a multifaceted post-translational modification that controls almost every process in eukaryotic cells.Recently,an effector protein of Legionella pneumophila,SdeA,was reported to mediate ubiquitination in a unique approach through two modifications of the R42 residue of ubiquitin(Ub),First to ADP-ribosylated Ub(ADPrUb),and then to phosphoribosylated Ub(PrUb),by its mono-ADP-ribosyltransferase(mART)and phosphodiesterase(PDE)domains,respectively.ADPrUb and PrUb were also shown to be novel and important Ub modifications influencing both the host ubiquitination and deubiquitination systems.however,the mechanism of SdeA-mediated Ub modifications remains unknown.In the work of this thesis,we report the crystal structures of SdeA in its ligand-free,Ub-bound,and Ub-NADH-bound states,respectively.The structure reveals that SdeAmART and SdeAPDE form a catalytic core.In the structure,the canonical ARTT and PN loops in SdeAmART undergo marked conformational changes.Notably,UbR72 is much closer to the active site of SdeAmART than UbR42 in the structure.Combined with biochemical and molecular dynamics simulation analysis,these results suggest that UbR72 Plays Like "Probe" Interaction with SdeAmART,and then pronounced movements occur in the sidechains of UbR72 and UbR42 during Ub ADP-ribosylation.Our study revealed the mechanism of SdeA-mediated ubiquitin modification and provided an important structural basis for the design of small molecule drugs targeting the SdeA family as potential antibiotics for the treatment of Legionella pneumonia and further study of the function of ADPrUb and PrUb.