title: Structural insight into brassinosteroid perception by BRI1.
abstract: 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.
authors.affiliation: Key Laboratory for Protein Sciences of Ministry of Education School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Ji
authors.initials: J
authors.lastname: She
authors.forename: Zhifu
authors.initials: Z
authors.lastname: Han
authors.forename: Tae-Wuk
authors.initials: TW
authors.lastname: Kim
authors.forename: Jinjing
authors.initials: J
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Cheng
authors.forename: Junbiao
authors.initials: J
authors.lastname: Chang
authors.forename: Shuai
authors.initials: S
authors.lastname: Shi
authors.forename: Jiawei
authors.initials: J
authors.lastname: Wang
authors.forename: Maojun
authors.initials: M
authors.lastname: Yang
authors.forename: Zhi-Yong
authors.initials: ZY
authors.lastname: Wang
authors.forename: Jijie
authors.initials: J
authors.lastname: Chai
mesh_terms: D017360:Arabidopsis / Q000737:chemistry* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D060406:Brassinosteroids; D002777:Cholestanols / Q000737:chemistry / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D011485:Protein Binding; D017510:Protein Folding; D011494:Protein Kinases / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013260:Steroids, Heterocyclic / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D002777:Cholestanols; D013260:Steroids, Heterocyclic; D011494:Protein Kinases; C108270:BRI1 protein, Arabidopsis; C023623:brassinolide