Structural insight into brassinosteroid perception by BRI1


Brassinosteroids are essential phytohormones that have crucial roles in plant growth and development. Perception of brassinosteroids requires an active complex of BRASSINOSTEROID-INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED KINASE 1 (BAK1). Recognized by the extracellular leucine-rich repeat (LRR) domain of BRI1, brassinosteroids induce a phosphorylation-mediated cascade to regulate gene expression. Here we present the crystal structures of BRI1(LRR) in free and brassinolide-bound forms. BRI1(LRR) exists as a monomer in crystals and solution independent of brassinolide. It comprises a helical solenoid structure that accommodates a separate insertion domain at its concave surface. Sandwiched between them, brassinolide binds to a hydrophobicity-dominating surface groove on BRI1(LRR). Brassinolide recognition by BRI1(LRR) is through an induced-fit mechanism involving stabilization of two interdomain loops that creates a pronounced non-polar surface groove for the hormone binding. Together, our results define the molecular mechanisms by which BRI1 recognizes brassinosteroids and provide insight into brassinosteroid-induced BRI1 activation.

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Figure 1: BRI1(LRR) has a helical solenoid structure.
Figure 2: Interaction of the insertion domain with LRRs.
Figure 3: Brassinolide binds a hydrophobic groove between the insertion domain and the inner surface of LRRs.
Figure 4: Brassinolide induces stabilization of two interdomain loops but no dimerization of BRI1(LRR).

Accession codes

Primary accessions

Protein Data Bank

Data deposits

The atomic coordinates and structure factors of BRI1(LRR) and the BRI1(LRR)–brassinolide complex have been deposited in the Protein Data Bank under the accession codes 3RGX and 3RGZ, respectively.


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We thank S. Huang and J. He at Shanghai Synchrotron Radiation Facility (SSRF) for assistance with data collection; J. Chory from the Salk Institute for providing the tritium-labelled brassinolide. This research was funded by the National Outstanding Young Scholar Science Foundation of National Natural Science Foundation of China grant no. 20101331722 to J. Chai and NIH R01GM066258 to Z.-Y.W.

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J. Chai, Z.H., J.S. and Z.-Y.W. designed the experiments. The binding assay was performed by T.-W.K. and the other assays by J.S., Z.H., Jinjing W., W.C., Jiawei W., M.Y., S.S. and J. Chang. Data were analysed by J. Chai, Z.H., J.S. and Z.-Y.W. J. Chai, Z.-Y.W. and Z.H. wrote the paper.

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Correspondence to Jijie Chai.

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She, J., Han, Z., Kim, T. et al. Structural insight into brassinosteroid perception by BRI1. Nature 474, 472–476 (2011).

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