View source for 9tp7


==Crystal structure of the C-terminal Ser/Thr phosphatase domain of the Kelch phosphatase BSU1 from Arabidopsis thaliana==
<StructureSection load='9tp7' size='340' side='right'caption='[[9tp7]], [[Resolution|resolution]] 2.10&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[9tp7]] is a 6 chain structure with sequence from [https://en.wikipedia.org/wiki/Arabidopsis_thaliana Arabidopsis thaliana]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=9TP7 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=9TP7 FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.1&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=GOL:GLYCEROL'>GOL</scene>, <scene name='pdbligand=TPO:PHOSPHOTHREONINE'>TPO</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=9tp7 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=9tp7 OCA], [https://pdbe.org/9tp7 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=9tp7 RCSB], [https://www.ebi.ac.uk/pdbsum/9tp7 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=9tp7 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/BSU1_ARATH BSU1_ARATH] Phosphatase that acts as a positive regulator of brassinosteroid (BR) signaling (PubMed:14977918, PubMed:21855796). Dephosphorylates BES1, a transcription factor that regulates the expression of BR-response genes, thereby playing an important role in the regulation of response to BRs (PubMed:14977918). Inactivates the negative regulator of BR signaling ASK7/BIN2 by dephosphorylation at 'Tyr-200' (PubMed:21855796).<ref>PMID:14977918</ref> <ref>PMID:21855796</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Brassinosteroids (BRs) are plant steroid hormones sensed by the membrane receptor kinase BRI1. Activation of BRI1 leads to the dephosphorylation of BZR1/BES1 transcription factors. Overexpression of the Kelch phosphatase BRI1 SUPPRESSOR 1 (BSU1) rescued the growth defects of bri1 mutants. Subsequent studies identified BSU1 as a protein tyrosine phosphatase, which promotes BR signaling by dephosphorylating a phosphotyrosine in the glycogen synthase kinase 3 BIN2. Crystal structures of the BSU1 phosphatase domain now reveal a high degree of structural similarity to protein phosphatase 1 (PP1), a eukaryotic serine/threonine phosphatase. Consistently, BSU1 efficiently dephosphorylated phosphothreonine- and phosphoserine-containing substrate peptides, but showed no detectable activity toward BIN2 and other phosphotyrosine substrates. A catalytically inactive BSU1 phosphatase domain suppresses the growth phenotypes of the Arabidopsis bri1-5 mutant and binds the BSU1 homologs BSL1-3. bsu1 and bsu1 bsl1 bsl2/3 loss-of-function mutants display wild-type-like BR responses, but exhibit stomatal patterning and fertility defects. Importantly, the PP1-like C-terminal tail of BSU1 is phosphorylated at Thr785 by a cyclin-dependent kinase complex. The phosphorylated tail binds to the BSU1 substrate-binding grooves, blocking access to the active site. Mutation of Thr785 to alanine activates BSU1, suggesting that Kelch phosphatases and PP1 share a common regulatory mechanism. Deletion of the Marchantia polymorpha Kelch phosphatase MpBSLM results in an undifferentiated cell mass phenotype, associated with the overactivation of a cell cycle reporter. Taken together, our experiments suggest that plant Kelch phosphatases act as PP1-like cell cycle regulators, rather than as tyrosine phosphatases in BR signaling.

Plant Kelch phosphatases are Ser/Thr phosphatases involved in cell cycle regulation.,Rico-Resendiz F, Pri-Tal O, Raia P, Moretti A, Chen H, Yu J, Broger L, Fuchs C, Hothorn LA, Loubery S, Hothorn M Proc Natl Acad Sci U S A. 2026 May 26;123(21):e2600591123. doi: , 10.1073/pnas.2600591123. Epub 2026 May 20. PMID:42166246<ref>PMID:42166246</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 9tp7" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Arabidopsis thaliana]]
[[Category: Large Structures]]
[[Category: Hothorn M]]
[[Category: Moretti A]]