title: An ABC transporter and an outer membrane lipoprotein participate in posttranslational activation of type VI secretion in Pseudomonas aeruginosa.
abstract: Pseudomonas aeruginosa is capable of injecting protein toxins into other bacterial cells through one of its three type VI secretion systems (T6SSs). The activity of this T6SS is tightly regulated on the posttranslational level by phosphorylation-dependent and -independent pathways. The phosphorylation-dependent pathway consists of a Threonine kinase/phosphatase pair (PpkA/PppA) that acts on a forkhead domain-containing protein, Fha1, and a periplasmic protein, TagR, that positively regulates PpkA. In the present work, we biochemically and functionally characterize three additional proteins of the phosphorylation-dependent regulatory cascade that controls T6S activation: TagT, TagS and TagQ. We show that similar to TagR, these proteins act upstream of the PpkA/PppA checkpoint and influence phosphorylation of Fha1 and, apparatus assembly and effector export. Localization studies demonstrate that TagQ is an outer membrane lipoprotein and TagR is associated with the outer membrane. Consistent with their homology to lipoprotein outer membrane localization (Lol) components, TagT and TagS form a stable inner membrane complex with ATPase activity. However, we find that outer membrane association of T6SS lipoproteins TagQ and TssJ1, and TagR, is unaltered in a ΔtagTS background. Notably, we found that TagQ is indispensible for anchoring of TagR to the outer membrane fraction. As T6S-dependent fitness of P. aeruginosa requires TagT, S, R and Q, we conclude that these proteins likely participate in a trans-membrane signalling pathway that promotes H1-T6SS activity under optimal environmental conditions.
authors: INSERM, UMR-S 1036, Biology of Cancer and Infection, Grenoble, France.
authors: Maria G
authors: MG
authors: Casabona
authors: Julie M
authors: JM
authors: Silverman
authors: Khady M
authors: KM
authors: Sall
authors: Frédéric
authors: F
authors: Boyer
authors: Yohann
authors: Y
authors: Couté
authors: Jessica
authors: J
authors: Poirel
authors: Didier
authors: D
authors: Grunwald
authors: Joseph D
authors: JD
authors: Mougous
authors: Sylvie
authors: S
authors: Elsen
authors: Ina
authors: I
authors: Attree
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D058947:Bacterial Secretion Systems / Q000502:physiology*; D001692:Biological Transport; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D055106:Genome-Wide Association Study; D008969:Molecular Sequence Data; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D058947:Bacterial Secretion Systems; D017346:Protein Serine-Threonine Kinases; D010744:Phosphoric Monoester Hydrolases