A bacterial inhibitor of host programmed cell death defenses is an E3 ubiquitin ligase.
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.
Janjusevic
Radmila
R
Laboratory of Structural Microbiology, Rockefeller University, New York, NY 10021, USA.
Abramovitch
Robert B
RB
Martin
Gregory B
GB
Stebbins
C Erec
CE
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*
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