View source for 3k09


==Crystal structure of the phosphorylation-site mutant S431D of the KaiC circadian clock protein==
<StructureSection load='3k09' size='340' side='right'caption='[[3k09]], [[Resolution|resolution]] 3.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3k09]] is a 6 chain structure with sequence from [https://en.wikipedia.org/wiki/Synechococcus_elongatus_PCC_7942_=_FACHB-805 Synechococcus elongatus PCC 7942 = FACHB-805]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3K09 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=3K09 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]] 3.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ATP:ADENOSINE-5-TRIPHOSPHATE'>ATP</scene>, <scene name='pdbligand=MG:MAGNESIUM+ION'>MG</scene>, <scene name='pdbligand=TPO:PHOSPHOTHREONINE'>TPO</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=3k09 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3k09 OCA], [https://pdbe.org/3k09 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=3k09 RCSB], [https://www.ebi.ac.uk/pdbsum/3k09 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=3k09 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/KAIC_SYNE7 KAIC_SYNE7] Core component of the KaiABC clock protein complex, which constitutes the main circadian regulator in cyanobacteria. Binds to DNA. The KaiABC complex may act as a promoter-nonspecific transcription regulator that represses transcription, possibly by acting on the state of chromosome compaction.<ref>PMID:9727980</ref> <ref>PMID:14709675</ref> 
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/k0/3k09_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=3k09 ConSurf].
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== Publication Abstract from PubMed ==
BACKGROUND: The circadian clock of the cyanobacterium Synechococcus elongatus can be reconstituted in vitro by three proteins, KaiA, KaiB and KaiC. Homo-hexameric KaiC displays kinase, phosphatase and ATPase activities; KaiA enhances KaiC phosphorylation and KaiB antagonizes KaiA. Phosphorylation and dephosphorylation of the two known sites in the C-terminal half of KaiC subunits, T432 and S431, follow a strict order (TS--&gt;pTS--&gt;pTpS--&gt;TpS--&gt;TS) over the daily cycle, the origin of which is not understood. To address this void and to analyze the roles of KaiC active site residues, in particular T426, we determined structures of single and double P-site mutants of S. elongatus KaiC. METHODOLOGY AND PRINCIPAL FINDINGS: The conformations of the loop region harboring P-site residues T432 and S431 in the crystal structures of six KaiC mutant proteins exhibit subtle differences that result in various distances between Thr (or Ala/Asn/Glu) and Ser (or Ala/Asp) residues and the ATP gamma-phosphate. T432 is phosphorylated first because it lies consistently closer to Pgamma. The structures of the S431A and T432E/S431A mutants reveal phosphorylation at T426. The environments of the latter residue in the structures and functional data for T426 mutants in vitro and in vivo imply a role in dephosphorylation. CONCLUSIONS AND SIGNIFICANCE: We provide evidence for a third phosphorylation site in KaiC at T426. T426 and S431 are closely spaced and a KaiC subunit cannot carry phosphates at both sites simultaneously. Fewer subunits are phosphorylated at T426 in the two KaiC mutants compared to phosphorylated T432 and/or S431 residues in the structures of wt and other mutant KaiCs, suggesting that T426 phosphorylation may be labile. The structures combined with functional data for a host of KaiC mutant proteins help rationalize why S431 trails T432 in the loss of its phosphate and shed light on the mechanisms of the KaiC kinase, ATPase and phosphatase activities.

Structures of KaiC circadian clock mutant proteins: a new phosphorylation site at T426 and mechanisms of kinase, ATPase and phosphatase.,Pattanayek R, Mori T, Xu Y, Pattanayek S, Johnson CH, Egli M PLoS One. 2009 Nov 26;4(11):e7529. PMID:19956664<ref>PMID:19956664</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 3k09" style="background-color:#fffaf0;"></div>

==See Also==
*[[Circadian clock protein 3D structures|Circadian clock protein 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Synechococcus elongatus PCC 7942 = FACHB-805]]
[[Category: Egli M]]
[[Category: Pattanayek R]]
[[Category: Pattanayek S]]