IP-MS analysis of Legionella pneumophila SdcB for detecting noncanonical ubiquitin crosslink by Legionella transglutaminase MavC.

To identify the unique ubiquitin conjugation to Legionella pneumophila SdcB, we investigated the modified SdcB by IP-MS analysis. We revealed that a Legionella transglutaminase MavC has a catalytic activity to crosslink Gln residues of ubiquitin to Lys residues of SdcB, resulting in a noncanonical ubiquitin modification, and that this modification abolish the enzymatic activity of SdcB as a E3 ubiquitin ligase.