Structure Determination Of Effector Protein VipF From Legionella Pneumophila

Legionella pneumophila is Gram-negative bacterium that exists in the aquatic environment of the world.When the person inhales the aerosol containing amoeba,the flagellated Legionella pneumophila enters the alveolar macrophages.Upon contact,Legionella pneumophila begins to alter the host and begins translocation through the Dot/Icm translocation system.More than 300 effector proteins enter the host and replicate in vivo,infecting the cells.Acetylation is one of most common protein post-translational modifications in eukaryotic cells.Acetyltransferases play a vital role in triggering acetyl group in acetyl-CoA transferred to its substrate.This process is conserved across different life branches and essential for the regulation of different physiological processes.The frequency of proteins being acetylated is tightly correlated with the complexity of the organism.VipF is one of the conserved effector proteins that can catalyze the acetylation process.Previous data inferred that VipF is a GNAT family N-acetyltransferase based on sequence conservation.However,the detail mechanisms for VipF binding to acetyl-CoA and its substrate is still unclear.In this thesis,we have determined the complex structures of VipF/acetyl-CoA and VipF/CoA by crystallography.The complex structures showed that VipF has a canonical acetyl-CoA binding pocket,confirming that it is belong to GNAT family acetyltransferase.We also compared these complex structures and revealed that there are some subtle conformational changes of VipF with different cofactors.Moreover,we also have determined the complex structures of VipF with its substrate chloramphenicol and VipF/chloramphenicol/acetyl-CoA and identified the binding pocket for VipF substrate.In summary,our study proposed a partial mechanism of VipF-mediated acetylation modification that provides an important improvement for further study of its physiological functions.