3S1A image
Deposition Date 2011-05-14
Release Date 2011-09-21
Last Version Date 2024-10-09
Entry Detail
PDB ID:
3S1A
Keywords:
Title:
Crystal structure of the phosphorylation-site double mutant S431E/T432E of the KaiC circadian clock protein
Biological Source:
Source Organism:
Host Organism:
Method Details:
Experimental Method:
Resolution:
3.00 Å
R-Value Free:
0.28
R-Value Work:
0.24
R-Value Observed:
0.26
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Circadian clock protein kinase kaiC
Gene (Uniprot):kaiC
Mutations:S431E, T432E
Chain IDs:A, F
Chain Length:525
Number of Molecules:2
Biological Source:Synechococcus elongatus
Polymer Type:polypeptide(L)
Molecule:Circadian clock protein kinase kaiC
Gene (Uniprot):kaiC
Mutations:S431E, T432E
Chain IDs:B, C, D, E
Chain Length:525
Number of Molecules:4
Biological Source:Synechococcus elongatus
Modified Residue
Compound ID Chain ID Parent Comp ID Details 2D Image
SEP A SER PHOSPHOSERINE
Primary Citation
Combined SAXS/EM Based Models of the S. elongatus Post-Translational Circadian Oscillator and its Interactions with the Output His-Kinase SasA.
Plos One 6 e23697 e23697 (2011)
PMID: 21887298 DOI: 10.1371/journal.pone.0023697

Abstact

The circadian clock in the cyanobacterium Synechococcus elongatus is composed of a post-translational oscillator (PTO) that can be reconstituted in vitro from three different proteins in the presence of ATP and a transcription-translation feedback loop (TTFL). The homo-hexameric KaiC kinase, phosphatase and ATPase alternates between hypo- and hyper-phosphorylated states over the 24-h cycle, with KaiA enhancing phosphorylation, and KaiB antagonizing KaiA and promoting KaiC subunit exchange. SasA is a His kinase that relays output signals from the PTO formed by the three Kai proteins to the TTFL. Although the crystal structures for all three Kai proteins are known, atomic resolution structures of Kai and Kai/SasA protein complexes have remained elusive. Here, we present models of the KaiAC and KaiBC complexes derived from solution small angle X-ray scattering (SAXS), which are consistent with previous EM based models. We also present a combined SAXS/EM model of the KaiC/SasA complex, which has two N-terminal SasA sensory domains occupying positions on the C-terminal KaiC ring reminiscent of the orientations adopted by KaiB dimers. Using EM we demonstrate that KaiB and SasA compete for similar binding sites on KaiC. We also propose an EM based model of the ternary KaiABC complex that is consistent with the sequestering of KaiA by KaiB on KaiC during the PTO dephosphorylation phase. This work provides the first 3D-catalogue of protein-protein interactions in the KaiABC PTO and the output pathway mediated by SasA.

Legend

Protein

Chemical

Disease

Primary Citation of related structures