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4dug

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== Structural highlights ==
== Structural highlights ==
<table><tr><td colspan='2'>[[4dug]] 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]. This structure supersedes the now removed PDB entry [http://oca.weizmann.ac.il/oca-bin/send-pdb?obs=1&id=3ua2 3ua2]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4DUG OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4DUG FirstGlance]. <br>
<table><tr><td colspan='2'>[[4dug]] 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]. This structure supersedes the now removed PDB entry [http://oca.weizmann.ac.il/oca-bin/send-pdb?obs=1&id=3ua2 3ua2]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4DUG OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4DUG FirstGlance]. <br>
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</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>
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</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 3.292&#8491;</td></tr>
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<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=4dug FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4dug OCA], [https://pdbe.org/4dug PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4dug RCSB], [https://www.ebi.ac.uk/pdbsum/4dug PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4dug ProSAT]</span></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=4dug FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4dug OCA], [https://pdbe.org/4dug PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4dug RCSB], [https://www.ebi.ac.uk/pdbsum/4dug PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4dug ProSAT]</span></td></tr>
</table>
</table>
== Function ==
== Function ==
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[[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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[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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<div style="background-color:#fffaf0;">
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== Publication Abstract from PubMed ==
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The circadian clock of the cyanobacterium Synechococcus elongatus can be reconstituted in vitro from three proteins, KaiA, KaiB, and KaiC in the presence of ATP, to tick in a temperature-compensated manner. KaiC, the central cog of this oscillator, forms a homohexamer with 12 ATP molecules bound between its N- and C-terminal domains and exhibits unusual properties. Both the N-terminal (CI) and C-terminal (CII) domains harbor ATPase activity, and the subunit interfaces between CII domains are the sites of autokinase and autophosphatase activities. Hydrolysis of ATP correlates with phosphorylation at threonine and serine sites across subunits in an orchestrated manner, such that first T432 and then S431 are phosphorylated, followed by dephosphorylation of these residues in the same order. Although structural work has provided insight into the mechanisms of ATPase and kinase, the location and mechanism of the phosphatase have remained enigmatic. From the available experimental data based on a range of approaches, including KaiC crystal structures and small-angle X-ray scattering models, metal ion dependence, site-directed mutagenesis (i.e., E318, the general base), and measurements of the associated clock periods, phosphorylation patterns, and dephosphorylation courses as well as a lack of sequence motifs in KaiC that are typically associated with known phosphatases, we hypothesized that KaiCII makes use of the same active site for phosphorylation and dephosphorlyation. We observed that wild-type KaiC (wt-KaiC) exhibits an ATP synthase activity that is significantly reduced in the T432A/S431A mutant. We interpret the first observation as evidence that KaiCII is a phosphotransferase instead of a phosphatase and the second that the enzyme is capable of generating ATP, both from ADP and P(i) (in a reversal of the ATPase reaction) and from ADP and P-T432/P-S431 (dephosphorylation). This new concept regarding the mechanism of dephosphorylation is also supported by the strikingly similar makeups of the active sites at the interfaces between alpha/beta heterodimers of F1-ATPase and between monomeric subunits in the KaiCII hexamer. Several KaiCII residues play a critical role in the relative activities of kinase and ATP synthase, among them R385, which stabilizes the compact form and helps kinase action reach a plateau, and T426, a short-lived phosphorylation site that promotes and affects the order of dephosphorylation.
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Dephosphorylation of the Core Clock Protein KaiC in the Cyanobacterial KaiABC Circadian Oscillator Proceeds via an ATP Synthase Mechanism.,Egli M, Mori T, Pattanayek R, Xu Y, Qin X, Johnson CH Biochemistry. 2012 Feb 13. PMID:22304631<ref>PMID:22304631</ref>
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From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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</div>
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<div class="pdbe-citations 4dug" style="background-color:#fffaf0;"></div>
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==See Also==
==See Also==

Current revision

Crystal Structure of Circadian Clock Protein KaiC E318A Mutant

PDB ID 4dug

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Proteopedia Page Contributors and Editors (what is this?)

OCA

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