Legionella pneumophila secretes ~300 effector proteins into the host cytosol during infection. These effectors exert multitude of biochemical activities and drive the maturation of Legionella containing vacuole (LCV) by hijacking several host defense pathways. Deletion of the effector SidJ negatively impacts legionella’s intra cellular growth. We recently showed that SidJ acts as a glutamylating enzyme that adopts a novel fold with distant similarity to kinase domains. SidJ shows no sequence or structural homology to mammalian glutamylating enzymes and contains two nucleotide-binding pockets. My proposal aims to address how SidJ recognizes its target proteins for glutamylation, how the two ATP-bindings pockets of SidJ co-ordinate to achieve target protein glutamylation and what host proteins does SidJ target especially after early stages of legionella infection.