View source for 8db3


==Crystal structure of KaiC with truncated C-terminal coiled-coil domain==
<StructureSection load='8db3' size='340' side='right'caption='[[8db3]], [[Resolution|resolution]] 2.90&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[8db3]] is a 3 chain structure with sequence from [https://en.wikipedia.org/wiki/Cereibacter_sphaeroides Cereibacter sphaeroides]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8DB3 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8DB3 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]] 2.9&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ADP:ADENOSINE-5-DIPHOSPHATE'>ADP</scene>, <scene name='pdbligand=SEP:PHOSPHOSERINE'>SEP</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=8db3 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8db3 OCA], [https://pdbe.org/8db3 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8db3 RCSB], [https://www.ebi.ac.uk/pdbsum/8db3 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8db3 ProSAT]</span></td></tr>
</table>
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== Publication Abstract from PubMed ==
Circadian rhythms play an essential part in many biological processes, and only three prokaryotic proteins are required to constitute a true post-translational circadian oscillator(1). The evolutionary history of the three Kai proteins indicates that KaiC is the oldest member and a central component of the clock(2). Subsequent additions of KaiB and KaiA regulate the phosphorylation state of KaiC for time synchronization. The canonical KaiABC system in cyanobacteria is well understood(3-6), but little is known about more ancient systems that only possess KaiBC. However, there are reports that they might exhibit a basic, hourglass-like timekeeping mechanism(7-9). Here we investigate the primordial circadian clock in Rhodobacter sphaeroides, which contains only KaiBC, to elucidate its inner workings despite missing KaiA. Using a combination of X-ray crystallography and cryogenic electron microscopy, we find a new dodecameric fold for KaiC, in which two hexamers are held together by a coiled-coil bundle of 12 helices. This interaction is formed by the carboxy-terminal extension of KaiC and serves as an ancient regulatory moiety that is later superseded by KaiA. A coiled-coil register shift between daytime and night-time conformations is connected to phosphorylation sites through a long-range allosteric network that spans over 140 A. Our kinetic data identify the difference in the ATP-to-ADP ratio between day and night as the environmental cue that drives the clock. They also unravel mechanistic details that shed light on the evolution of self-sustained oscillators.

From primordial clocks to circadian oscillators.,Pitsawong W, Padua RAP, Grant T, Hoemberger M, Otten R, Bradshaw N, Grigorieff N, Kern D Nature. 2023 Apr;616(7955):183-189. doi: 10.1038/s41586-023-05836-9. Epub 2023 , Mar 22. PMID:36949197<ref>PMID:36949197</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 8db3" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Cereibacter sphaeroides]]
[[Category: Large Structures]]
[[Category: Bradshaw N]]
[[Category: Grant T]]
[[Category: Grigorieff N]]
[[Category: Hoemberger MS]]
[[Category: Kern D]]
[[Category: Otten R]]
[[Category: Padua RAP]]
[[Category: Pitsawong W]]