8qt5 | pdb_00008qt5
Crystal structure of Arabidopsis thaliana 14-3-3 isoform lambda in complex with a phosphopeptide from the transcription factor BZR1.
Structural highlights
Function14336_ARATH Is associated with a DNA binding complex that binds to the G box, a well-characterized cis-acting DNA regulatory element found in plant genes (By similarity). Specific negative regulator of slow-vacuolar (SV) ion channel. Mediates F-actin dynamics possibly through inhibiting ADF1 phosphorylation (PubMed:26345162). Negative regulator of freezing tolerance that modulates cold-responsive C-repeat-binding factors (CBF) DREB1A and DREB1B proteins stability by facilitating their ubiquitin-mediated degradation when activated by CRPK1-mediated phosphorylation in freezing conditions; this processus is counteracted by B1L (PubMed:28344081, PubMed:31297122).[1] [2] [3] [4] BZR1_ARATH Transcriptional repressor that binds to the brassinosteroid (BR) response element (BRRE) 5'-CGTG(T/C)G-3' in gene promoter. Regulates positively the brassinosteroid-signaling pathway (PubMed:33324437). Mediates downstream growth responses and negative feedback regulation of brassinosteroid biosynthesis. Promotes growth. Modulates ovule initiation and development by monitoring the expression of genes related to ovule development (e.g. HLL, ANT, and AP2). Negatively regulates the abscisic acid (ABA) signaling pathway during the post-germination stage (PubMed:33324437).[5] [6] [7] Publication Abstract from PubMedBrassinosteroids (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-epsilon subgroup. 14-3-3lambda and 14-3-3omega 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 14-3-3lambda with all three linear motifs. Notably, quadruple loss-of-function mutants from the non-epsilon 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. Mechanistic insights into the function of 14-3-3 proteins as negative regulators of brassinosteroid signaling in Arabidopsis.,Obergfell E, Hohmann U, Moretti A, Chen H, Hothorn M Plant Cell Physiol. 2024 May 23:pcae056. doi: 10.1093/pcp/pcae056. PMID:38783418[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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