The crystal structure of LidA,a translocated substrate of the Legionella pneumophila type IV secretion system

Dear Editor,Legionella pneumophila,a gram-neg-ative bacterium,is the causative agent of Legionnaires’pneumonia by infecting human lung macrophages(Muder et al.,1986).Upon uptake into macrophages,the bacteria are internalized to escape the endocytic pathway and lysosomal network,and establish the Legionella-containing vacuole(LCV)as an intracel-lular replicative organelle(Roy et al.,1998).The LCV hijacks and recruits the early secretory ER-derived vesicles and transforms them into ER-like vacuole.Within the specialized ER-like vacuole,L.pneumophila replicates to a high den-sity and subsequently kills the host cell by lysing the host cell membrane.The released bacteria can infect neighboring cells to initiate a new round of infection(Tilney et al.,2001).