title: The Legionella autoinducer synthase LqsA produces an alpha-hydroxyketone signaling molecule.
abstract: The opportunistic pathogen Legionella pneumophila replicates in human lung macrophages and in free-living amoebae. To accommodate the transfer between host cells, L. pneumophila switches from a replicative to a transmissive phase. L. pneumophila harbors a gene cluster homologous to the Vibrio cholerae cqsAS quorum sensing system, encoding a putative autoinducer synthase (lqsA) and a sensor kinase (lqsS), which flank a response regulator (lqsR). LqsR is an element of the L. pneumophila virulence regulatory network, which promotes pathogen-host cell interactions and inhibits entry into the replicative growth phase. Here, we show that lqsA functionally complements a V. cholerae cqsA autoinducer synthase deletion mutant and, upon expression in L. pneumophila or Escherichia coli, produces the diffusible signaling molecule LAI-1 (Legionella autoinducer-1). LAI-1 is distinct from CAI-1 (Cholerae autoinducer-1) and was identified as 3-hydroxypentadecan-4-one using liquid chromatography coupled to high resolution tandem mass spectrometry. The activity of both LqsA and CqsA was abolished upon mutation of a conserved lysine, and covalent binding of the cofactor pyridoxal 5'-phosphate to this lysine was confirmed by mass spectrometry. Thus, LqsA and CqsA belong to a family of pyridoxal 5'-phosphate-dependent autoinducer synthases, which produce the alpha-hydroxyketone signaling molecules LAI-1 and CAI-1.
authors.affiliation: Institute of Microbiology, ETH Zürich, Zürich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Spirig
authors.forename: André
authors.initials: A
authors.lastname: Tiaden
authors.forename: Patrick
authors.initials: P
authors.lastname: Kiefer
authors.forename: Carmen
authors.initials: C
authors.lastname: Buchrieser
authors.forename: Julia A
authors.initials: JA
authors.lastname: Vorholt
authors.forename: Hubert
authors.initials: H
authors.lastname: Hilbi
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D001665:Binding Sites; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D007659:Ketones / Q000737:chemistry*; D016952:Legionella pneumophila / Q000378:metabolism*; D013058:Mass Spectrometry; D008954:Models, Biological; D008956:Models, Chemical; D010641:Phenotype; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry / Q000502:physiology*; D011732:Pyridoxal Phosphate / Q000737:chemistry; D015398:Signal Transduction; D013997:Time Factors; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D007659:Ketones; D011732:Pyridoxal Phosphate; D011494:Protein Kinases