View source for 4ijm


==Crystal structure of circadian clock protein KaiC A422V mutant==
<StructureSection load='4ijm' size='340' side='right'caption='[[4ijm]], [[Resolution|resolution]] 3.35&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4ijm]] 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=4IJM OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4IJM 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]] 3.352&#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=PO4:PHOSPHATE+ION'>PO4</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=4ijm FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4ijm OCA], [https://pdbe.org/4ijm PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4ijm RCSB], [https://www.ebi.ac.uk/pdbsum/4ijm PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4ijm 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> 
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== Publication Abstract from PubMed ==
The Synechococcus elongatus KaiA, KaiB, and KaiC proteins in the presence of ATP generate a post-translational oscillator that runs in a temperature-compensated manner with a period of 24 h. KaiA dimer stimulates phosphorylation of KaiC hexamer at two sites per subunit, T432 and S431, and KaiB dimers antagonize KaiA action and induce KaiC subunit exchange. Neither the mechanism of KaiA-stimulated KaiC phosphorylation nor that of KaiB-mediated KaiC dephosphorylation is understood in detail at present. We demonstrate here that the A422V KaiC mutant sheds light on the former mechanism. It was previously reported that A422V is less sensitive to dark pulse-induced phase resetting and has a reduced amplitude of the KaiC phosphorylation rhythm in vivo. A422 maps to a loop (422-loop) that continues toward the phosphorylation sites. By pulling on the C-terminal peptide of KaiC (A-loop), KaiA removes restraints from the adjacent 422-loop whose increased flexibility indirectly promotes kinase activity. We found in the crystal structure that A422V KaiC lacks phosphorylation at S431 and exhibits a subtle, local conformational change relative to wild-type KaiC. Molecular dynamics simulations indicate higher mobility of the 422-loop in the absence of the A-loop and mobility differences in other areas associated with phosphorylation activity between wild-type and mutant KaiCs. The A-loop-422-loop relay that informs KaiC phosphorylation sites of KaiA dimer binding propagates to loops from neighboring KaiC subunits, thus providing support for a concerted allosteric mechanism of phosphorylation.

Loop-Loop Interactions Regulate KaiA-Stimulated KaiC Phosphorylation in the Cyanobacterial KaiABC Circadian Clock.,Egli M, Pattanayek R, Sheehan JH, Xu Y, Mori T, Smith JA, Johnson CH Biochemistry. 2013 Feb 7. PMID:23351065<ref>PMID:23351065</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 4ijm" style="background-color:#fffaf0;"></div>

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