Structural basis for flg22-induced activation of the Arabidopsis FLS2-BAK1 immune complex

Yadong Sun, Lei Li, Alberto P Macho, Zhifu Han, Zehan Hu, Cyril Zipfel, Jian-Min Zhou, Jijie Chai

Research output: Contribution to journalArticlepeer-review

536 Citations (Scopus)


Flagellin perception in Arabidopsis is through recognition of its highly conserved N-terminal epitope (flg22) by flagellin-sensitive 2 (FLS2). Flg22 binding induces FLS2 heteromerization with BRASSINOSTEROID INSENSITIVE 1-associated kinase 1 (BAK1) and their reciprocal activation followed by plant immunity. Here, we report the crystal structure of FLS2 and BAK1 ectodomains complexed with flg22 at 3.06 angstroms. A conserved and a nonconserved site from the inner surface of the FLS2 solenoid recognize the C- and N-terminal segment of flg22, respectively, without oligomerization or conformational changes in the FLS2 ectodomain. Besides directly interacting with FLS2, BAK1 acts as a co-receptor by recognizing the C terminus of the FLS2-bound flg22. Our data reveal the molecular mechanisms underlying FLS2-BAK1 complex recognition of flg22 and provide insight into the immune receptor complex activation.
Original languageEnglish
Pages (from-to)624-628
Number of pages5
Issue number6158
Publication statusPublished - 1 Nov 2013


  • Antigen-Antibody Complex
  • Arabidopsis
  • Arabidopsis Proteins
  • Crystallography, X-Ray
  • Flagellin
  • Protein Kinases
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases

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