title: A bacterial inhibitor of host programmed cell death defenses is an E3 ubiquitin ligase.
abstract: The Pseudomonas syringae protein AvrPtoB is translocated into plant cells, where it inhibits immunity-associated programmed cell death (PCD). The structure of a C-terminal domain of AvrPtoB that is essential for anti-PCD activity reveals an unexpected homology to the U-box and RING-finger components of eukaryotic E3 ubiquitin ligases, and we show that AvrPtoB has ubiquitin ligase activity. Mutation of conserved residues involved in the binding of E2 ubiquitin-conjugating enzymes abolishes this activity in vitro, as well as anti-PCD activity in tomato leaves, which dramatically decreases virulence. These results show that Pseudomonas syringae uses a mimic of host E3 ubiquitin ligases to inactivate plant defenses.
authors.affiliation: Laboratory of Structural Microbiology, Rockefeller University, New York, NY 10021, USA.
authors.forename: Radmila
authors.initials: R
authors.lastname: Janjusevic
authors.forename: Robert B
authors.initials: RB
authors.lastname: Abramovitch
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Martin
authors.forename: C Erec
authors.initials: CE
authors.lastname: Stebbins
mesh_terms: D017209:Apoptosis; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018551:Solanum lycopersicum / Q000276:immunology / Q000382:microbiology*; D018716:Molecular Mimicry; D016296:Mutagenesis; D010935:Plant Diseases / Q000382:microbiology; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D044224:Pseudomonas syringae / Q000201:enzymology* / Q000472:pathogenicity; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C081695:avrPto protein, Pseudomonas syringae; C097310:UBE2D3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases; C084354:Pto protein, Lycopersicon; D017346:Protein Serine-Threonine Kinases