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==Solution Structure of the C-terminal Domain of Thermosynechococcus elongatus KaiA (ThKaiA180C); Averaged Minimized Structure==
==Solution Structure of the C-terminal Domain of Thermosynechococcus elongatus KaiA (ThKaiA180C); Averaged Minimized Structure==
<StructureSection load='1q6a' size='340' side='right'caption='[[1q6a]], [[NMR_Ensembles_of_Models | 1 NMR models]]' scene=''>
<StructureSection load='1q6a' size='340' side='right'caption='[[1q6a]]' scene=''>
== Structural highlights ==
== Structural highlights ==
<table><tr><td colspan='2'>[[1q6a]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Theeb Theeb]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1Q6A OCA]. For a <b>guided tour on the structure components</b> use [http://proteopedia.org/fgij/fg.htm?mol=1Q6A FirstGlance]. <br>
<table><tr><td colspan='2'>[[1q6a]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Thermosynechococcus_vestitus_BP-1 Thermosynechococcus vestitus BP-1]. Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1Q6A OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1Q6A FirstGlance]. <br>
</td></tr><tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">KaiA ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=197221 THEEB])</td></tr>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">Solution NMR</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://proteopedia.org/fgij/fg.htm?mol=1q6a FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1q6a OCA], [http://pdbe.org/1q6a PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=1q6a RCSB], [http://www.ebi.ac.uk/pdbsum/1q6a PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=1q6a 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=1q6a FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1q6a OCA], [https://pdbe.org/1q6a PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1q6a RCSB], [https://www.ebi.ac.uk/pdbsum/1q6a PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1q6a ProSAT]</span></td></tr>
</table>
</table>
== Function ==
== Function ==
[[http://www.uniprot.org/uniprot/KAIA_THEEB KAIA_THEEB]] Component of the KaiABC clock protein complex, which constitutes the main circadian regulator in cyanobacteria. The KaiABC complex may act as a promoter-nonspecific transcription regulator that represses transcription, possibly by acting on the state of chromosome compaction. In the complex, it enhances the phosphorylation status of KaiC. In contrast, the presence of KaiB in the complex decreases the phosphorylation status of KaiC, suggesting that KaiB acts by antagonizing the interaction between KaiA and KaiC. A KaiA dimer is sufficient to enhance KaiC hexamer phosphorylation.  
[https://www.uniprot.org/uniprot/KAIA_THEVB KAIA_THEVB] Key component of the KaiABC oscillator complex, which constitutes the main circadian regulator in cyanobacteria. Complex composition changes during the circadian cycle to control KaiC phosphorylation. KaiA stimulates KaiC autophosphorylation, while KaiB sequesters KaiA, leading to KaiC autodephosphorylation. KaiA binding to the KaiC CII domain during the subjective day yields KaiA(2-4):KaiC(6) complexes which stimulate KaiC autophosphorylation. Phospho-Ser-431 KaiC accumulation triggers binding of KaiB during the subjective night to form the KaiB(6):KaiC(6) complex, leading to changes in the output regulators CikA and SasA. KaiB(6):KaiC(6) formation exposes a site for KaiA binding on KaiB that sequesters KaiA from KaiC's CII domain, making the KaiC(6):KaiB(6):KaiA(12) complex resulting in KaiC autodephosphorylation. Complete dephosphorylation of KaiC leads to dissociation of KaiA(2):KaiB(1), completing 1 cycle of the Kai oscillator (By similarity). Formation of the KaiB:KaiC complex is promoted by KaiA, helping switch KaiC from its autophosphorylation to autodephosphatase function (PubMed:24112939).[UniProtKB:Q79PF6]<ref>PMID:24112939</ref>  Binds oxidized quinones via the N-terminal PsR domain, allowing it to sense redox changes and possibly mediate clock input.[UniProtKB:Q79PF6]
== Evolutionary Conservation ==
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
[[Image:Consurf_key_small.gif|200px|right]]
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</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=1q6a ConSurf].
</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=1q6a ConSurf].
<div style="clear:both"></div>
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
KaiA is a two-domain circadian clock protein in cyanobacteria, acting as the positive element in a feedback loop that sustains the oscillation. The structure of the N-terminal domain of KaiA is that of a pseudo-receiver, similar to those of bacterial response regulators, which likely interacts with components of the clock-resetting pathway. The C-terminal domain of KaiA is highly conserved among cyanobacteria and enhances the autokinase activity of KaiC. Here we present the NMR structure of the C-terminal domain of KaiA from the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1. This domain adopts a novel all alpha-helical homodimeric structure. Several mutations known to affect the period of the circadian oscillator are shown to be located at an exposed groove near the dimer interface. This NMR structure and a 21-A-resolution electron microscopy structure of the hexameric KaiC particle allow us to postulate a mode of KaiA-KaiC interaction, in which KaiA binds a linker region connecting two globular KaiC domains.
NMR structure of the KaiC-interacting C-terminal domain of KaiA, a circadian clock protein: implications for KaiA-KaiC interaction.,Vakonakis I, Sun J, Wu T, Holzenburg A, Golden SS, LiWang AC Proc Natl Acad Sci U S A. 2004 Feb 10;101(6):1479-84. Epub 2004 Jan 28. PMID:14749515<ref>PMID:14749515</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 1q6a" style="background-color:#fffaf0;"></div>


==See Also==
==See Also==
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</StructureSection>
</StructureSection>
[[Category: Large Structures]]
[[Category: Large Structures]]
[[Category: Theeb]]
[[Category: Thermosynechococcus vestitus BP-1]]
[[Category: Golden, S S]]
[[Category: Golden SS]]
[[Category: Holzenburg, A]]
[[Category: Holzenburg A]]
[[Category: LiWang, A C]]
[[Category: LiWang AC]]
[[Category: Sun, J]]
[[Category: Sun J]]
[[Category: Vakonakis, I]]
[[Category: Vakonakis I]]
[[Category: All alpha-helix protein]]
[[Category: Circadian clock protein]]
[[Category: Homodimer]]

Revision as of 09:01, 17 April 2024

Solution Structure of the C-terminal Domain of Thermosynechococcus elongatus KaiA (ThKaiA180C); Averaged Minimized StructureSolution Structure of the C-terminal Domain of Thermosynechococcus elongatus KaiA (ThKaiA180C); Averaged Minimized Structure

Structural highlights

1q6a is a 2 chain structure with sequence from Thermosynechococcus vestitus BP-1. Full experimental information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:Solution NMR
Resources:FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

KAIA_THEVB Key component of the KaiABC oscillator complex, which constitutes the main circadian regulator in cyanobacteria. Complex composition changes during the circadian cycle to control KaiC phosphorylation. KaiA stimulates KaiC autophosphorylation, while KaiB sequesters KaiA, leading to KaiC autodephosphorylation. KaiA binding to the KaiC CII domain during the subjective day yields KaiA(2-4):KaiC(6) complexes which stimulate KaiC autophosphorylation. Phospho-Ser-431 KaiC accumulation triggers binding of KaiB during the subjective night to form the KaiB(6):KaiC(6) complex, leading to changes in the output regulators CikA and SasA. KaiB(6):KaiC(6) formation exposes a site for KaiA binding on KaiB that sequesters KaiA from KaiC's CII domain, making the KaiC(6):KaiB(6):KaiA(12) complex resulting in KaiC autodephosphorylation. Complete dephosphorylation of KaiC leads to dissociation of KaiA(2):KaiB(1), completing 1 cycle of the Kai oscillator (By similarity). Formation of the KaiB:KaiC complex is promoted by KaiA, helping switch KaiC from its autophosphorylation to autodephosphatase function (PubMed:24112939).[UniProtKB:Q79PF6][1] Binds oxidized quinones via the N-terminal PsR domain, allowing it to sense redox changes and possibly mediate clock input.[UniProtKB:Q79PF6]

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

See Also

References

  1. ↑ Tseng R, Chang YG, Bravo I, Latham R, Chaudhary A, Kuo NW, Liwang A. Cooperative KaiA-KaiB-KaiC interactions affect KaiB/SasA competition in the circadian clock of cyanobacteria. J Mol Biol. 2014 Jan 23;426(2):389-402. PMID:24112939 doi:10.1016/j.jmb.2013.09.040
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