This domain found in the SidE bacterial effector protein mediates the mono-ADP-ribosylation of ubiquitin, which is then ligated to host proteins by the Pfam:PF12252 domain [1].

1: Mechanism of phosphoribosyl-ubiquitination mediated by a single Legionella effector. Akturk A, Wasilko DJ, Wu X, Liu Y, Zhang Y, Qiu J, Luo ZQ, Reiter KH, Brzovic PS, Klevit RE, Mao Y; Nature. 2018;557:729-733. PMID:29795346