2fd4 | pdb_00002fd4
Crystal Structure of AvrPtoB (436-553)
Structural highlights
Function[HPAB2_PSESM] Effector protein involved in gene-for-gene resistance in tomato plants. It is recognized by the host Pto resistance protein and elicits Pto and Prf-dependent hypersensitive response (HR) and programmed cell death (PCD), resulting in host immunity. In susceptible plants, acts as a virulence factor by suppressing PCD and HR-based plant immunity. This function requires its E3 ubiquitin ligase activity probably by recruiting E2 enzymes and transferring ubiquitin molecules to cellular proteins involved in regulation of PCD and targeting them for degradation. Also, induces expression of host genes involved in ethylene biosynthesis and signaling, in particular ACO1 and ACO2, encoding the ethylene-forming enzyme ACC oxidase.[1] [2] [3] [4] [5] Publication Abstract from PubMedThe 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. A bacterial inhibitor of host programmed cell death defenses is an E3 ubiquitin ligase.,Janjusevic R, Abramovitch RB, Martin GB, Stebbins CE Science. 2006 Jan 13;311(5758):222-6. Epub 2005 Dec 22. PMID:16373536[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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