A Pseudomonas aeruginosa type VI secretion phospholipase D effector targets both prokaryotic and eukaryotic cells.
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The paper characterises PldB, the paralogous phospholipase D effector encoded at PA5089, together with its three immunity proteins.
"Here we describe the characterization of a P. aeruginosa H3-T6SS-dependent phospholipase D effector, PldB, and its three tightly linked cognate immunity proteins."
Genetic and biochemical analyses of a eukaryotic-like phospholipase D of Pseudomonas aeruginosa suggest horizontal acquisition and a role for persistence in a chronic pulmonary infection model.
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Cloned pldA expresses a ~116 kDa protein with calcium-regulated phospholipase D activity localised to the periplasm.
"The pldA gene was cloned and shown to express an approximately 116 kDa protein with calcium-regulated PLD activity that is localized to the periplasm."
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pldA is absent from some strains and is always linked to a vgr gene, suggesting horizontal acquisition.
"When present, pldA is always linked to an open reading frame (ORF), ORF4, and a gene (vgrA1) encoding a protein homologous to Vgr from Escherichia coli."
Diverse type VI secretion phospholipases are functionally plastic antibacterial effectors.
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PldA is Tle5PA; purified protein releases choline from phosphatidylcholine and the activity depends on the catalytic histidine His855.
"Consistent with prior observations, Tle5PA catalyzes the release of choline from phosphatidylcholine (PC), in a manner dependent upon a predicted catalytic histidine residue (His855)"
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In target cells the effector acts mainly on phosphatidylethanolamine, and death follows accumulation of phosphatidic acid.
"Taken together, these data strongly suggest that Tle5PA-imposed cell death occurs through PA accumulation via PLD activity, primarily directed against PE."
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The Tle5 family is defined by dual HxKxxxxD motifs of phospholipase D enzymes.
"Four of the families (Tle1-4) exhibit the GxSxG motif common in esterases and many lipases, while the fifth (Tle5) possesses dual HxKxxxxD motifs found in PLD enzymes"
Structural insights into PA3488-mediated inactivation of Pseudomonas aeruginosa PldA.
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The PldA structure shows the conserved HKD catalytic core, with a eukaryotic-like active-site conformation.
"As noted, as a member of the PLD family, PldA possesses the highly conserved HxK(xxxx)nD consensus sequence."
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PldA accommodates a wide range of phospholipid substrates, unlike the narrower eukaryotic enzymes.
"In contrast to the substrate preferences of eukaryotic PLDs, PldA can accommodate a wide range of phospholipids as substrates"
Delivery of the Pseudomonas aeruginosa Phospholipase Effectors PldA and PldB in a VgrG- and H2-T6SS-Dependent Manner.
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PldA is encoded by PA3487 and PldB by PA5089; they are distinct genes with distinct cognate VgrG proteins.
"vgrG5 (PA5090, blue) is encoded directly upstream of pldB (PA5089, cyan)"
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PldA secretion depends on VgrG4b and is restored by complementation.
"Here, we show that the lack of PldA secretion is solely due to the absence of VgrG4b since PldA release is restored by complementing the vgrG4b mutant"
Gene Ontology annotation through association of InterPro records with GO terms
Gene Ontology annotation based on Enzyme Commission mapping
Annotation inferences using phylogenetic trees