Molecular mechanism of elongation factor 1A inhibition by a Legionella pneumophila glycosyltransferase

Legionnaires' disease is caused by a lethal colonization of alveolar macrophages with the Gram-negative bacterium Legionella pneumophila. LpGT (L. pneumophila glucosyltransferase: also known as Lgt1) has recently been identified as a virulence factor, shutting Clown protein synthesis in the human cell by specific glucosylation of EF1A (elongation factor 1A), using all Unknown mole of substrate recognition and a retaining mechanism for glycosyl transfer. We have determined the crystal Structure of LpGT in complex with Substrates, revealing a GT-A fold with two unusual protruding domains. Through structure-guided mutagenesis of LpGT, several residues essential for binding of the UDP-glucose-donor and EF1A-acceptor substrates were identified, which also affected L. pneumophila virulence as demonstrated by microinjection studies. Together, these results suggested that a positively charged EF1A loop binds to a negatively charged conserved groove oil the LpGT structure. and that two asparagine residues are essential for catalysis. Furthermore, we showed that two further L. pneumophila glycosyltransferases possessed the conserved UDP-glucose-binding sites and EF1A-binding grooves. and are. like LpGT, translocated into the macrophage through the Icm/Dot (intracellular multiplication/defect in organelle trafficking) system.