6bn0

From Proteopedia

Avirulence protein 4 (Avr4) from Cladosporium fulvum bound to the hexasaccharide of chitin

PDB ID 6bn0

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Structural highlights

6bn0 is a 4 chain structure with sequence from Fulvia fulva. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 1.95Å
Ligands:	,
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

AVR4_PASFU This necrosis-inducing peptide induces a hypersensitive response on Cf-4 tomato genotypes. Race-specific elicitors are compounds which only induce defense responses in genotypes of host plants which are resistant to the pathogenic race that produces the elicitor, but not in susceptible genotypes.

Publication Abstract from PubMed

Effectors are microbial-derived secreted proteins with an essential function in modulating host immunity during infections. CfAvr4, an effector protein from the tomato pathogen Cladosporium fulvum and the founding member of a fungal effector family, promotes parasitism through binding fungal chitin and protecting it from chitinases. Binding of Avr4 to chitin is mediated by a carbohydrate-binding module of family 14 (CBM14), an abundant CBM across all domains of life. To date, the structural basis of chitin-binding by Avr4 effector proteins and of recognition by the cognate Cf-4 plant immune receptor are still poorly understood. Using X-ray crystallography, we solved the crystal structure of CfAvr4 in complex with chitohexaose [(GlcNAc)6] at 1.95A resolution. This is the first co-crystal structure of a CBM14 protein together with its ligand that further reveals the molecular mechanism of (GlcNAc)6 binding by Avr4 effector proteins and CBM14 family members in general. The structure showed that two molecules of CfAvr4 interact through the ligand and form a three-dimensional molecular sandwich that encapsulates two (GlcNAc)6 molecules within the dimeric assembly. Contrary to previous assumptions made with other CBM14 members, the chitohexaose-binding domain (ChBD) extends to the entire length of CfAvr4 with the reducing end of (GlcNAc)6 positioned near the N-terminus and the non-reducing end at the C-terminus. Site-directed mutagenesis of residues interacting with (GlcNAc)6 enabled the elucidation of the precise topography and amino acid composition of Avr4's ChBD and further showed that these residues do not individually mediate the recognition of CfAvr4 by the Cf-4 immune receptor. Instead, the studies highlighted the dependency of Cf-4-mediated recognition on CfAvr4's stability and resistance against proteolysis in the leaf apoplast, and provided the evidence for structurally separating intrinsic function from immune receptor recognition in this effector family.

Structure of the Cladosporium fulvum Avr4 effector in complex with (GlcNAc)6 reveals the ligand-binding mechanism and uncouples its intrinsic function from recognition by the Cf-4 resistance protein.,Hurlburt NK, Chen LH, Stergiopoulos I, Fisher AJ PLoS Pathog. 2018 Aug 27;14(8):e1007263. doi: 10.1371/journal.ppat.1007263., eCollection 2018 Aug. PMID:30148881^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Hurlburt NK, Chen LH, Stergiopoulos I, Fisher AJ. Structure of the Cladosporium fulvum Avr4 effector in complex with (GlcNAc)6 reveals the ligand-binding mechanism and uncouples its intrinsic function from recognition by the Cf-4 resistance protein. PLoS Pathog. 2018 Aug 27;14(8):e1007263. doi: 10.1371/journal.ppat.1007263., eCollection 2018 Aug. PMID:30148881 doi:http://dx.doi.org/10.1371/journal.ppat.1007263