2QKE

Wild Type Crystal Structure of Full Length Circadian Clock Protein KaiB from Thermosynechococcus elongatus BP-1

Summary for 2QKE

• Entry DOI: 10.2210/pdb2qke/pdb
• Related: 1R5P 1VGL 1WWJ
• Descriptor: Circadian clock protein kaiB (2 entities in total)
• Functional Keywords: cyanobacterial circadian clock protein, circadian clock protein
• Biological source: Synechococcus elongatus
• Total number of polymer chains: 6
• Total formula weight: 72240.28

Authors

Pattanayek, R.,Egli, M.,Pattanayek, S. (deposition date: 2007-07-10, release date: 2008-06-17, Last modification date: 2023-08-30)

Primary citation

Pattanayek, R.,Williams, D.R.,Pattanayek, S.,Mori, T.,Johnson, C.H.,Stewart, P.L.,Egli, M.
Structural model of the circadian clock KaiB-KaiC complex and mechanism for modulation of KaiC phosphorylation.
Embo J., 27:1767-1778, 2008

PubMed Abstract: The circadian clock of the cyanobacterium Synechococcus elongatus can be reconstituted in vitro by the KaiA, KaiB and KaiC proteins in the presence of ATP. The principal clock component, KaiC, undergoes regular cycles between hyper- and hypo-phosphorylated states with a period of ca. 24 h that is temperature compensated. KaiA enhances KaiC phosphorylation and this enhancement is antagonized by KaiB. Throughout the cycle Kai proteins interact in a dynamic manner to form complexes of different composition. We present a three-dimensional model of the S. elongatus KaiB-KaiC complex based on X-ray crystallography, negative-stain and cryo-electron microscopy, native gel electrophoresis and modelling techniques. We provide experimental evidence that KaiB dimers interact with KaiC from the same side as KaiA and for a conformational rearrangement of the C-terminal regions of KaiC subunits. The enlarged central channel and thus KaiC subunit separation in the C-terminal ring of the hexamer is consistent with KaiC subunit exchange during the dephosphorylation phase. The proposed binding mode of KaiB explains the observation of simultaneous binding of KaiA and KaiB to KaiC, and provides insight into the mechanism of KaiB's antagonism of KaiA.

PubMed: 18497745
DOI: 10.1038/emboj.2008.104

Experimental method

X-RAY DIFFRACTION (2.7 Å)