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Cell Host Microbe. 2011 Mar 17;9(3):200-211. doi: 10.1016/j.chom.2011.02.009.

Structural and functional analysis of a plant resistance protein TIR domain reveals interfaces for self-association, signaling, and autoregulation.

Author information

1
CSIRO Plant Industry, Canberra, Australian Capital Territory 2601, Australia.
2
School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, University of Queensland, Brisbane, Queensland 4072, Australia; Centre for Infectious Disease Research, University of Queensland, Brisbane, Queensland 4072, Australia.
3
Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, Victoria 3010, Australia.
4
School of Chemistry and Molecular Biosciences, Institute for Molecular Bioscience, Division of Chemistry and Structural Biology, University of Queensland, Brisbane, Queensland 4072, Australia; Centre for Infectious Disease Research, University of Queensland, Brisbane, Queensland 4072, Australia. Electronic address: b.kobe@uq.edu.au.
5
CSIRO Plant Industry, Canberra, Australian Capital Territory 2601, Australia. Electronic address: peter.dodds@csiro.au.

Abstract

The Toll/interleukin-1 receptor (TIR) domain occurs in animal and plant immune receptors. In the animal Toll-like receptors, homodimerization of the intracellular TIR domain is required for initiation of signaling cascades leading to innate immunity. By contrast, the role of the TIR domain in cytoplasmic nucleotide-binding/leucine-rich repeat (NB-LRR) plant immune resistance proteins is poorly understood. L6 is a TIR-NB-LRR resistance protein from flax (Linum usitatissimum) that confers resistance to the flax rust phytopathogenic fungus (Melampsora lini). We determine the crystal structure of the L6 TIR domain and show that, although dispensable for pathogenic effector protein recognition, the TIR domain alone is both necessary and sufficient for L6 immune signaling. We demonstrate that the L6 TIR domain self-associates, most likely forming a homodimer. Analysis of the structure combined with site-directed mutagenesis suggests that self-association is a requirement for immune signaling and reveals distinct surface regions involved in self-association, signaling, and autoregulation.

PMID:
21402359
PMCID:
PMC3142617
DOI:
10.1016/j.chom.2011.02.009
[Indexed for MEDLINE]
Free PMC Article

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