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

Farhad Forouhar, Yue Yang, Dhirendra Kumar, Yang Chen, Eyal Fridman, Sang Wook Park, Yiwen Chiang, Thomas B. Acton, Gaetano T. Montelione, Eran Pichersky, Daniel F. Klessig, Liang Tong

Research output: Contribution to journalArticlepeer-review

244 Scopus citations

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-Å resolution. The structures confirm that SABP2 is a member of the α/β 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.

Original languageEnglish (US)
Pages (from-to)1773-1778
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number5
DOIs
StatePublished - Feb 1 2005

All Science Journal Classification (ASJC) codes

  • General

Keywords

  • Salicylic acid
  • Salicylic-acid-binding protein
  • Systemic acquired resistance
  • α/β hydrolase

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