Biological Assembly 1  

 3D View: Structure | Electron Density | Ligand Interaction

Global Symmetry: Cyclic - C2  (3D View)
Global Stoichiometry: Homo 4-mer - A4 

Biological assembly 1 assigned by authors.

Macromolecule Content

• Total Structure Weight: 125.94 kDa 
• Atom Count: 9105 
• Residue Count: 1028 
• Unique protein chains: 1

1XKL

Crystal Structure of Salicylic Acid-binding Protein 2 (SABP2) from Nicotiana tabacum, NESG Target AR2241

• DOI: 10.2210/pdb1XKL/pdb

• Classification: STRUCTURAL GENOMICS, UNKNOWN FUNCTION
• Organism(s): Nicotiana tabacum
• Expression System: Escherichia coli
• Mutation(s): Yes 


• Deposited: 2004-09-29 Released: 2004-11-30 
• Deposition Author(s): Forouhar, F., Chen, Y., Chiang, Y., Acton, T.B., Montelione, G.T., Hunt, J.F., Tong, L., Northeast Structural Genomics Consortium (NESG)

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.00 Å
• R-Value Free: 0.234 
• R-Value Work: 0.190 
• R-Value Observed: 0.190 

Literature

Structural and biochemical studies identify tobacco SABP2 as a methyl salicylate esterase and implicate it in plant innate immunity

Forouhar, F., Yang, Y., Kumar, D., Chen, Y., Fridman, E.

(2005) Proc Natl Acad Sci U S A 102: 1773-1778

• PubMed: 15668381 
• DOI: 10.1073/pnas.0409227102
• Primary Citation of Related Structures:  
  1XKL, 1Y7I, 1Y7H


• PubMed Abstract: 
  

Salicylic acid (SA) is a critical signal for the activation of plant defense responses against pathogen infections. We recently identified SA-binding protein 2 (SABP2) from tobacco as a protein that displays high affinity for SA and plays a crucial role in the activation of systemic acquired resistance to plant pathogens. Here we report the crystal structures of SABP2, alone and in complex with SA at up to 2.1-A resolution. The structures confirm that SABP2 is a member of the alpha/beta hydrolase superfamily of enzymes, with Ser-81, His-238, and Asp-210 as the catalytic triad. SA is bound in the active site and is completely shielded from the solvent, consistent with the high affinity of this compound for SABP2. Our biochemical studies reveal that SABP2 has strong esterase activity with methyl salicylate as the substrate, and that SA is a potent product inhibitor of this catalysis. Modeling of SABP2 with MeSA in the active site is consistent with all these biochemical observations. Our results suggest that SABP2 may be required to convert MeSA to SA as part of the signal transduction pathways that activate systemic acquired resistance and perhaps local defense responses as well.

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Organizational Affiliation: 

Department of Biological Sciences, Northeast Structural Genomics Consortium, Columbia University, New York, NY 10027, USA.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
salicylic acid-binding protein 2	A, B, C, D	273	Nicotiana tabacum	Mutation(s): 9  Gene Names: AAR87711, SABP2 EC: 3.1.1
Find proteins for Q6RYA0 (Nicotiana tabacum) Explore Q6RYA0  Go to UniProtKB:  Q6RYA0

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
STH	A, B, C, D	2-AMINO-4H-1,3-BENZOXATHIIN-4-OL C8 H9 N O2 S DVFUKUONLVBBEH-SFYZADRCSA-N

Modified Residues  1 Unique
ID	Chains	Type	Formula	2D Diagram	Parent
MSE	A,B,C,D	L-PEPTIDE LINKING	C5 H11 N O2 Se		MET

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.00 Å
• R-Value Free: 0.234 
• R-Value Work: 0.190 
• R-Value Observed: 0.190 
• Space Group: P 2₁ 2₁ 2

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 136.457	α = 90
b = 167.773	β = 90
c = 44.831	γ = 90

Software Package:

Software Name	Purpose
CNS	refinement
DENZO	data reduction
SCALEPACK	data scaling
SnB	phasing
SOLVE	phasing

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2004-09-29 
• Released Date: 2004-11-30 
Deposition Author(s): Forouhar, F., Chen, Y., Chiang, Y., Acton, T.B., Montelione, G.T., Hunt, J.F., Tong, L., Northeast Structural Genomics Consortium (NESG)

Revision History 

• Version 1.0: 2004-11-30
  Type: Initial release
  
• Version 1.1: 2008-04-30
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance
• Version 1.3: 2011-11-16
  Changes: Atomic model
• Version 1.4: 2017-10-11
  Changes: Refinement description