: / : / regulation of phosphorelay signal transduction system / negative regulation of circadian rhythm / entrainment of circadian clock / negative regulation of phosphorylation / protein serine/threonine/tyrosine kinase activity / Hydrolases; Acting on acid anhydrides; Acting on acid anhydrides to facilitate cellular and subcellular movement / regulation of circadian rhythm / circadian rhythm ...: / : / regulation of phosphorelay signal transduction system / negative regulation of circadian rhythm / entrainment of circadian clock / negative regulation of phosphorylation / protein serine/threonine/tyrosine kinase activity / Hydrolases; Acting on acid anhydrides; Acting on acid anhydrides to facilitate cellular and subcellular movement / regulation of circadian rhythm / circadian rhythm / non-specific serine/threonine protein kinase / phosphorylation / protein serine kinase activity / protein serine/threonine kinase activity / regulation of DNA-templated transcription / magnesium ion binding / ATP hydrolysis activity / DNA binding / ATP binding / identical protein binding / plasma membrane / cytoplasm Similarity search - Function
Journal: J Mol Biol / Year: 2013 Title: CryoEM and molecular dynamics of the circadian KaiB-KaiC complex indicates that KaiB monomers interact with KaiC and block ATP binding clefts. Authors: Seth A Villarreal / Rekha Pattanayek / Dewight R Williams / Tetsuya Mori / Ximing Qin / Carl H Johnson / Martin Egli / Phoebe L Stewart / Abstract: The circadian control of cellular processes in cyanobacteria is regulated by a posttranslational oscillator formed by three Kai proteins. During the oscillator cycle, KaiA serves to promote ...The circadian control of cellular processes in cyanobacteria is regulated by a posttranslational oscillator formed by three Kai proteins. During the oscillator cycle, KaiA serves to promote autophosphorylation of KaiC while KaiB counteracts this effect. Here, we present a crystallographic structure of the wild-type Synechococcus elongatus KaiB and a cryo-electron microscopy (cryoEM) structure of a KaiBC complex. The crystal structure shows the expected dimer core structure and significant conformational variations of the KaiB C-terminal region, which is functionally important in maintaining rhythmicity. The KaiBC sample was formed with a C-terminally truncated form of KaiC, KaiC-Δ489, which is persistently phosphorylated. The KaiB-KaiC-Δ489 structure reveals that the KaiC hexamer can bind six monomers of KaiB, which form a continuous ring of density in the KaiBC complex. We performed cryoEM-guided molecular dynamics flexible fitting simulations with crystal structures of KaiB and KaiC to probe the KaiBC protein-protein interface. This analysis indicated a favorable binding mode for the KaiB monomer on the CII end of KaiC, involving two adjacent KaiC subunits and spanning an ATP binding cleft. A KaiC mutation, R468C, which has been shown to affect the affinity of KaiB for KaiC and lengthen the period in a bioluminescence rhythm assay, is found within the middle of the predicted KaiBC interface. The proposed KaiB binding mode blocks access to the ATP binding cleft in the CII ring of KaiC, which provides insight into how KaiB might influence the phosphorylation status of KaiC.
History
Deposition
May 16, 2013
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Header (metadata) release
Jun 26, 2013
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Map release
Jul 3, 2013
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Update
Sep 4, 2013
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Current status
Sep 4, 2013
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Supramolecule #1000: KaiB in complex with KaiC(489del)
Supramolecule
Name: KaiB in complex with KaiC(489del) / type: sample / ID: 1000 Details: Visualization of the sample showed complexes of KaiBC and KaiC. Oligomeric state: One Hexamer of KaiC binds to 6 monomers of KaiB Number unique components: 2
Molecular weight
Theoretical: 510 KDa
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Macromolecule #1: KaiB
Macromolecule
Name: KaiB / type: protein_or_peptide / ID: 1 / Name.synonym: Circadian clock protein KaiB / Number of copies: 6 / Oligomeric state: Dimer / Recombinant expression: Yes
Model: Tecnai Polara / Image courtesy: FEI Company
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Image processing
Details
The particles were selected manually.
CTF correction
Details: Each micrograph
Final reconstruction
Algorithm: OTHER / Resolution.type: BY AUTHOR / Resolution: 16.0 Å / Resolution method: FSC 0.5 CUT-OFF Software - Name: FREALIGN, Rubinstein_2_Refinement_package, IMAGIC Details: Final map was calculated from 3 data sets. / Number images used: 195226
Final two d classification
Number classes: 2000
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