8QTT

Crystal structure of a C-terminally truncated version of Arabidopsis thaliana 14-3-3 omega in complex with a phosphopeptide from the inhibitor protein BKI1.

Summary for 8QTT

• Entry DOI: 10.2210/pdb8qtt/pdb
• Related: 8QTF
• Descriptor: 14-3-3-like protein GF14 omega, BRI1 kinase inhibitor 1, FORMIC ACID, ... (5 entities in total)
• Functional Keywords: 14-3-3, brassinosteroid signaling, phosphopeptide, transcription factor, signal transduction, protein binding, kinase inhibitor
• Biological source: Arabidopsis thaliana (thale cress); More
• Total number of polymer chains: 20
• Total formula weight: 279344.56

Authors

Hothorn, M.,Obergfell, E. (deposition date: 2023-10-13, release date: 2023-11-15, Last modification date: 2024-10-16)

Primary citation

Obergfell, E.,Hohmann, U.,Moretti, A.,Chen, H.,Hothorn, M.
Mechanistic insights into the function of 14-3-3 proteins as negative regulators of brassinosteroid signaling in Arabidopsis.
Plant Cell.Physiol., 2024

PubMed Abstract: Brassinosteroids (BRs) are vital plant steroid hormones sensed at the cell surface by a membrane signaling complex comprising the receptor kinase BRI1 and a SERK-family co-receptor kinase. Activation of this complex lead to dissociation of the inhibitor protein BKI1 from the receptor and to differential phosphorylation of BZR1/BES1 transcription factors by the glycogen synthase kinase 3 protein BIN2. Many phosphoproteins of the BR signaling pathway, including BRI1, SERKs, BKI1 and BZR1/BES1 can associate with 14-3-3 proteins. In this study, we use quantitative ligand binding assays to define the minimal 14-3-3 binding sites in the N-terminal lobe of the BRI1 kinase domain, in BKI1, and in BZR1 from Arabidopsis thaliana. All three motifs require to be phosphorylated to specifically bind 14-3-3s with mid- to low micromolar affinity. BR signaling components display minimal isoform preference within the 14-3-3 non-ε subgroup. 14-3-3λ and 14-3-3ω isoform complex crystal structures reveal that BKI1 and BZR1 bind as canonical type II 14-3-3 linear motifs. Disruption of key amino acids in the phosphopeptide binding site through mutation impairs the interaction of 14-3-3λ with all three linear motifs. Notably, quadruple loss-of-function mutants from the non-ε group exhibit gain-of-function brassinosteroid signaling phenotypes, suggesting a role for 14-3-3 proteins as overall negative regulators of the BR pathway. Collectively, our work provides further mechanistic and genetic evidence for the regulatory role of 14-3-3 proteins at various stages of the brassinosteroid signaling cascade.

PubMed: 38783418
DOI: 10.1093/pcp/pcae056

Experimental method

X-RAY DIFFRACTION (2.35 Å)