Catalytic mechanism of an Actin-dependent adenylyltransferase involved in ubiquitin signaling

The two effectors LnaB and MavL of Legionella pneumophila coordinate the conversion of phosphoribosyl ubiquitin (PR-Ub) released by reversal of ubiquitination induced by members of the SidE effector family into functional Ub. LnaB acts as an actin-dependent phosphoryl AMPylase that converts PR-Ub into ADP-ribosylated (ADPR)-Ub. Catalysis by LnaB requires the novel conserved S-HxxxE motif present in a large family of bacterial toxins. Here we uncovered a novel adenylylation mechanism involved in two-step ATP hydrolysis.