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Science. 2017 Mar 17;355(6330):1181-1184. doi: 10.1126/science.aag3218. Epub 2017 Mar 16.

Structures of the cyanobacterial circadian oscillator frozen in a fully assembled state.

Author information

1
Biomolecular Mass Spectrometry and Proteomics and Netherlands Proteomics Center, Bijvoet Center for Biomolecular Research, and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, Netherlands.
2
Max Planck Institute of Biochemistry, Department of Molecular Structural Biology, D-82152 Martinsried, Germany.
3
Institute for Synthetic Microbiology, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany.
4
Max Planck Institute of Biochemistry, Department of Molecular Structural Biology, D-82152 Martinsried, Germany. a.j.r.heck@uu.nl f.g.forster@uu.nl.
5
Cryo-electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH, Utrecht, Netherlands.
6
Biomolecular Mass Spectrometry and Proteomics and Netherlands Proteomics Center, Bijvoet Center for Biomolecular Research, and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, Netherlands. a.j.r.heck@uu.nl f.g.forster@uu.nl.

Abstract

Cyanobacteria have a robust circadian oscillator, known as the Kai system. Reconstituted from the purified protein components KaiC, KaiB, and KaiA, it can tick autonomously in the presence of adenosine 5'-triphosphate (ATP). The KaiC hexamers enter a natural 24-hour reaction cycle of autophosphorylation and assembly with KaiB and KaiA in numerous diverse forms. We describe the preparation of stoichiometrically well-defined assemblies of KaiCB and KaiCBA, as monitored by native mass spectrometry, allowing for a structural characterization by single-particle cryo-electron microscopy and mass spectrometry. Our data reveal details of the interactions between the Kai proteins and provide a structural basis to understand periodic assembly of the protein oscillator.

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PMID:
28302852
DOI:
10.1126/science.aag3218
[Indexed for MEDLINE]

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