title: The structure of Legionella pneumophila LegK4 type four secretion system (T4SS) effector reveals a novel dimeric eukaryotic-like kinase.
abstract: Bacterial pathogens subvert signalling pathways to promote invasion and/or replication into the host. LegK1-4 proteins are eukaryotic-like serine/threonine kinases that are translocated by the Dot/Icm type IV secretion system (T4SS) of several Legionella pneumophila strains. We present the crystal structures of an active fragment of the LegK4 protein in apo and substrate-bound states. The structure of LegK4(1-445) reveals a eukaryotic-like kinase domain flanked by a novel cap domain and a four-helix bundle. The protein self-assembles through interactions mediated by helices αF and αG that generate a dimeric interface not previously observed in a protein kinase. The helix αG is displaced compared to previous kinase structures, and its role in stabilization of the activation loop is taken on by the dimerisation interface. The apo-form of the protein has an open conformation with a disordered P-loop but a structured activation segment in absence of targeted phosphorylation. The nucleotide-binding site of LegK4 contains an unusual set of residues that mediate non-canonical interactions with AMP-PNP. Nucleotide binding results in limited changes in the active site, suggesting that LegK4 constitutive kinase activity does not depend on phosphorylation of the activation loop but on the stabilizing effects of the dimer.
authors.affiliation: UMR 5086 BMSSI CNRS-Université de Lyon, Institut de Biologie et Chimie des Protéines, 7 Passage du Vercors, F-69367 Lyon Cedex 07, France.
authors.forename: Ali
authors.initials: A
authors.lastname: Flayhan
authors.affiliation: UMR 5086 BMSSI CNRS-Université de Lyon, Institut de Biologie et Chimie des Protéines, 7 Passage du Vercors, F-69367 Lyon Cedex 07, France.
authors.forename: Célia
authors.initials: C
authors.lastname: Bergé
authors.affiliation: Legionella Pathogenesis Group, International Center for Infectiology Research, Université de Lyon Lyon, France.|INSERM U1111 Lyon, France.|Ecole Normale Suptérieure de Lyon Lyon, France.|Centre International de Recherche en Infectiologie, Université Lyon 1 Lyon, France.|CNRS, UMR5308 Lyon, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Baïlo
authors.affiliation: Legionella Pathogenesis Group, International Center for Infectiology Research, Université de Lyon Lyon, France.|INSERM U1111 Lyon, France.|Ecole Normale Suptérieure de Lyon Lyon, France.|Centre International de Recherche en Infectiologie, Université Lyon 1 Lyon, France.|CNRS, UMR5308 Lyon, France.
authors.forename: Patricia
authors.initials: P
authors.lastname: Doublet
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom.
authors.forename: Richard
authors.initials: R
authors.lastname: Bayliss
authors.affiliation: Department of Biochemistry, University of Leicester, Leicester LE1 9HN, United Kingdom.
authors.forename: Laurent
authors.initials: L
authors.lastname: Terradot
mesh_terms: D001665:Binding Sites; D020134:Catalytic Domain; D016952:Legionella pneumophila / Q000378:metabolism*; D008958:Models, Molecular; D009711:Nucleotides / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism*; D055503:Protein Multimerization; D055550:Protein Stability; D000069319:Type IV Secretion Systems / Q000378:metabolism*
chemical_list: D009711:Nucleotides; D000069319:Type IV Secretion Systems; D011494:Protein Kinases