PSI Structural Biology Knowledgebase

PSI | Structural Biology Knowledgebase
Header Icons
E-Collection

Related Articles
Community-Nominated Targets
July 2015
Drug Discovery: Solving the Structure of an Anti-hypertension Drug Target
July 2015
Retrospective: 7,000 Structures Closer to Understanding Biology
July 2015
Design and Evolution: Unveiling Translocator Proteins
June 2015
Signaling with DivL
May 2015
Signaling: A Platform for Opposing Functions
May 2015
Signaling: Securing Lipid-Protein Partnership
May 2015
Dynamic DnaK
March 2015
Iron-Sulfur Cluster Biosynthesis
December 2014
Mitochondrion: Flipping for UCP2
December 2014
Mitochondrion: Setting a New TRAP1
December 2014
Power in Numbers
August 2014
Quorum Sensing: A Groovy New Component
August 2014
Quorum Sensing: E. coli Gets Involved
August 2014
iTRAQing the Ubiquitinome
July 2014
Microbiome: The Dynamics of Infection
September 2013
Protein-Nucleic Acid Interaction: A Modified SAM to Modify tRNA
July 2013
Protein-Nucleic Acid Interaction: Versatile Glutamate
July 2013
PDZ Domains
April 2013
Alpha-Catenin Connections
March 2013
Cell-Cell Interaction: A FERM Connection
March 2013
Cell-Cell Interaction: Magic Structure from Microcrystals
March 2013
Cell-Cell Interaction: Modulating Self Recognition Affinity
March 2013
Bacterial Hemophores
January 2013
Archaeal Lipids
December 2012
Membrane Proteome: Capturing Multiple Conformations
December 2012
Lethal Tendencies
October 2012
Symmetry from Asymmetry
October 2012
A signal sensing switch
September 2012
Regulatory insights
September 2012
AlkB Homologs
August 2012
Budding ensemble
August 2012
Targeting Enzyme Function with Structural Genomics
July 2012
The machines behind the spindle assembly checkpoint
June 2012
Chaperone interactions
April 2012
Pilus Assembly Protein TadZ
April 2012
Revealing the Nuclear Pore Complex
March 2012
Topping off the proteasome
March 2012
Twist to open
March 2012
Disordered Proteins
February 2012
Analyzing an allergen
January 2012
Making Lipopolysaccharide
January 2012
Pulling on loose ends
January 2012
Terminal activation
December 2011
The Perils of Protein Secretion
November 2011
Bacterial Armor
October 2011
TLR4 regulation: heads or tails?
October 2011
Ribose production on demand
September 2011
Moving some metal
August 2011
Looking for lipids
July 2011
Ribofuranosyl Binding Protein
June 2011
A molecular switch for neuronal growth
May 2011
Cell wall recycler
May 2011
Added benefits
April 2011
NMR challenges current protein hydration dogma
March 2011
Nitrile Reductase QueF
March 2011
Tip formin
March 2011
Inhibiting factor
February 2011
PASK staying active
February 2011
Tryptophanyl-tRNA Synthetase
February 2011
Regulating nitrogen assimilation
January 2011
Subtle shifts
January 2011
Nitrobindin
December 2010
Function following form
October 2010
tRNA Isopentenyltransferase MiaA
August 2010
Importance of extension for integrin
June 2010
Phytochrome
April 2010
Alg13 Subunit of N-Acetylglucosamine Transferase
February 2010
Hemolysin BL
January 2010
Secretagogin
December 2009
Two-component signaling
December 2009
Network coverage
November 2009
Pseudouridine Synthase TruA
November 2009
Unusual cell division
October 2009
Toxin-antitoxin VapBC-5
September 2009
Salicylic Acid Binding Protein 2
August 2009
Proofreading RNA
July 2009
Ykul structure solves bacterial signaling puzzle
July 2009
Hda and DNA Replication
June 2009
Controlling p53
May 2009
Mitotic checkpoint control
May 2009
Ribonuclease and Ribonuclease Inhibitor
April 2009
The elusive helicase
April 2009
Aquaglyceroporin
March 2009
High-energy storage system
February 2009
A new class of bacterial E3 ubiquitination enzymes
January 2009
Poly(A) RNA recognition
January 2009
Activating BAX
December 2008
Scavenger Decapping Enzyme DcpS
November 2008
Bacteriophage Lambda cII Protein
October 2008
New metal-binding domain
October 2008
Blocking AmtB
September 2008
T-Rex
September 2008
Aspartate Dehydrogenase
August 2008
RNase T
July 2008
Chronophin
May 2008

Research Themes Cell biology

Salicylic Acid Binding Protein 2

PSI-SGKB [doi:10.3942/psi_sgkb/fm_2009_8]
Featured System - August 2009
Short description: Centuries ago, both the ancient Greeks and native Americans discovered that willow bark and other plants can dull pain.

Centuries ago, both the ancient Greeks and native Americans discovered that willow bark and other plants can dull pain. By analyzing these traditional cures, scientists in the nineteenth century extracted the active molecule, salicylic acid, and developed a modified molecule with better drug properties, acetylsalicylic acid or aspirin. In our bodies, aspirin blocks an enzyme that builds one of the molecules of pain signaling. Plants, on the other hand, use salicylic acid for an entirely different type of signaling.

Defensive Action

Plants have developed a complex and multi-layered system to protect themselves from attack by bacteria and viruses. When a leaf gets infected, for instance by tobacco mosaic virus, the local cells make the ultimate sacrifice, inducing a form of programmed cell death. This helps control the spread of the virus by proactively removing all infectable cells in the neighborhood. At the same time, the plant launches a more systemic defense. It sends a signal to all of its distant parts, telling them to build defensive proteins and ready themselves for attack. These defenses are costly, and may result in stunted growth, but this is better than completely losing the battle against the attacker.

Aromatic Signals

Methyl salicylate, the methyl ester of salicylic acid, is one of the signals that spreads through plants, readying them for attack. Methyl salicylate is a familiar molecule, since it provides the distinctive taste and smell of wintergreen flavorings. It is used as a neutral messenger, which is created by cells under attack and delivered to cells throughout the plant. Then, the enzyme SABP2 (salicylic acid binding protein 2) takes methyl salicylate and cleaves off the methyl group, releasing active salicylic acid, which then stimulates the production of defensive proteins in the target cells.

SABP2 in Action

SABP2 was originally discovered based on its ability to bind to salicylic acid (hence its name), but the recent structure of the protein solved by researchers at the NESG revealed its role in cleavage of methyl salicylate and inhibition of the reaction by the product, salicylic acid. The structure, available in PDB entry 1y7i, shows that SABP2 is one of a class of alpha/beta hydrolase enzymes that cleave small esters and other molecules. The active site completely surrounds the molecule, recognizing both the distinctive aromatic ring and the acidic group. A catalytic triad reminiscent of the digestive serine proteases performs the cleavage reaction. Based on this structure, researchers have designed analogues of salicylic acid to probe signaling methods in other plants. To explore this structure in more detail, you can click on the image below for an interactive Jmol view of the active site.

The JSmol tab below displays an interactive JSmol.

Guanine Nucleotide Exchange Factor Vav1 and Rho GTPase Rac1 (PDB entry 3bji)

Vav1 (in blue and green) interacts with two key switch loops in Rac1 (the switch loops are colored bright red in this representation). The typical interaction between guanine nucleotide exchange factors and GTPases involves other regions of the GTPase, but since the Vav1 structure is stabilized by the small cysteine-rich domain (colored green here, with two zinc ions in magenta), it can focus its attention on the switch loops. This makes Vav1 more promiscuous than other guanine exchange factors.

References

  1. Forouhar, F., Yang, Y., Kumar, D., Chen, Y., Fridman, E., Park, S. W., Chiang, Y., Acton, T. B., Montelione, G. T., Pichersky, E., Klessig, D. F. and Tong, L. (2005) Structural and biochemical studies identify tobacco SABP2 as a methyl salicylate esterase and implicate it in plant innate immunity. PNAS 102, 1773-1778.

  2. Park, S. W., Liu, P. P., Forouhar, F., Vlot, A. C., Tong, L., Tietjen, K. and Klessig, D. F. (2009) Use of a synthetic salicylic acid analog to investigate the roles of methyl salicylate and its esterases in plant disease resistance. J. Biol. Chem. 284, 7307-7317.

  3. Park, S. W., Kaimoyo, E., Kumar, D., Mosher, S. and Klessig, D. F. (2007) Methyl salicylate is a critical mobile signal for plant systemic acquired resistance. Science 318, 113-116.

  4. Loake, G. and Grant, M. (2007) Salicylic acid in plant defence--the players and protagonists. Curr. Op. Plant Biol. 10, 456-472.

  5. Durrant, W. E. and Dong, X. (2004) System acquired resistance. Annu. Rev. Phytopathol. 42, 185-209.

Structural Biology Knowledgebase ISSN: 1758-1338
Funded by a grant from the National Institute of General Medical Sciences of the National Institutes of Health