Identification and modelling of a PPM protein phosphatase fold in the Legionella pneumophila deAMPylase SidD

The intracellular parasitic bacterium Legionella pneumophila subverts host vesicle transport through reversible AMPylation of Rab1. The effector enzyme for deAMPylation is SidD. Here a complete PPM protein phosphatase fold catalytic domain in SidD is identified and modelled. The SidD model reveals insertions and deletions near the metal ion containing catalytic site which presumably determine its novel activity. It also sheds light on possible substrate binding residues and highlights the lack of an obvious group to act as general acid during reaction. Assignment of a PPM fold to SidD offers an important pointer towards identification of further deAMPylases.

► Legionella pneumophila de AMPylase SidD contains a PPM protein phosphatase fold catalytic domain.
► PPM fold hitherto associated exclusively with protein phosphatase activity.
► Modelling sheds light on substrate binding and catalysis.
► Results suggest further deAMPylases may be found in protein phosphatase superfamilies.