8xat
Crystal structure of AtARR1(RD-DBD)
Structural highlights
FunctionARR1_ARATH Transcriptional activator that binds specifically to the DNA sequence 5'-[AG]GATT-3'. Functions as a response regulator involved in His-to-Asp phosphorelay signal transduction system. Phosphorylation of the Asp residue in the receiver domain activates the ability of the protein to promote the transcription of target genes. Could directly activate some type-A response regulators in response to cytokinins. Regulates SHY2 by binding to its promoter (PubMed:19039136). Involved in the root-meristem size determination through the regulation of cell differentiation (PubMed:17363254).[1] [2] [3] [4] Publication Abstract from PubMedThe phytohormone cytokinin has various roles in plant development, including meristem maintenance, vascular differentiation, leaf senescence, and regeneration. Prior investigations have revealed that cytokinin acts via a phosphorelay similar to the two-component system by which bacteria sense and respond to external stimuli. The eventual targets of this phosphorelay are type-B ARABIDOPSIS RESPONSE REGULATORS (B-ARRs), containing the conserved N-terminal receiver domain (RD), middle DNA binding domain (DBD), and C-terminal transactivation domain. While it has been established for two decades that the phosphoryl transfer from a specific histidyl residue in ARABIDOPSIS HIS PHOSPHOTRANSFER PROTEINS (AHPs) to an aspartyl residue in the RD of B-ARRs results in a rapid transcriptional response to cytokinin, the underlying molecular basis remains unclear. In this work, we determine the crystal structures of the RD-DBD of ARR1 (ARR1(RD-DBD)) as well as the ARR1(DBD)-DNA complex from Arabidopsis. Analyses of the ARR1(DBD)-DNA complex have revealed the structural basis for sequence-specific recognition of the GAT trinucleotide by ARR1. In particular, comparing the ARR1(RD-DBD) and ARR1(DBD)-DNA structures reveals that unphosphorylated ARR1(RD-DBD) exists in a closed conformation with extensive contacts between the RD and DBD. In vitro and vivo functional assays have further suggested that phosphorylation of the RD weakens its interaction with DBD, subsequently permits the DNA binding capacity of DBD, and promotes the transcriptional activity of ARR1. Our findings thus provide mechanistic insights into phosphorelay activation of gene transcription in response to cytokinin. The structure of B-ARR reveals the molecular basis of transcriptional activation by cytokinin.,Zhou CM, Li JX, Zhang TQ, Xu ZG, Ma ML, Zhang P, Wang JW Proc Natl Acad Sci U S A. 2024 Jan 16;121(3):e2319335121. doi: , 10.1073/pnas.2319335121. Epub 2024 Jan 10. PMID:38198526[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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