title: Structures of the cyanobacterial circadian oscillator frozen in a fully assembled state.
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.
authors.affiliation: 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.
authors.forename: Joost
authors.identifier: 0000-0002-9310-8226
authors.initials: J
authors.lastname: Snijder
authors.affiliation: Max Planck Institute of Biochemistry, Department of Molecular Structural Biology, D-82152 Martinsried, Germany.
authors.forename: Jan M
authors.identifier: 0000-0002-9121-1764
authors.initials: JM
authors.lastname: Schuller
authors.affiliation: Institute for Synthetic Microbiology, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany.
authors.forename: Anika
authors.identifier: 0000-0001-9674-0510
authors.initials: A
authors.lastname: Wiegard
authors.affiliation: 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.
authors.forename: Philip
authors.identifier: 0000-0001-5062-7723
authors.initials: P
authors.lastname: Lössl
authors.affiliation: Institute for Synthetic Microbiology, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany.
authors.forename: Nicolas
authors.identifier: 0000-0002-6981-397X
authors.initials: N
authors.lastname: Schmelling
authors.affiliation: Institute for Synthetic Microbiology, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Düsseldorf, D-40225 Düsseldorf, Germany.
authors.forename: Ilka M
authors.identifier: 0000-0002-0856-8667
authors.initials: IM
authors.lastname: Axmann
authors.affiliation: Max Planck Institute of Biochemistry, Department of Molecular Structural Biology, D-82152 Martinsried, Germany.
authors.forename: Jürgen M
authors.identifier: 0000-0002-6402-8315
authors.initials: JM
authors.lastname: Plitzko
authors.affiliation: 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.|Cryo-electron Microscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH, Utrecht, Netherlands.
authors.forename: Friedrich
authors.identifier: 0000-0002-6044-2746
authors.initials: F
authors.lastname: Förster
authors.affiliation: 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.
authors.forename: Albert J R
authors.identifier: 0000-0002-2405-4404
authors.initials: AJ
authors.lastname: Heck
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry* / Q000648:ultrastructure; D057906:Circadian Clocks; D002940:Circadian Rhythm; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000737:chemistry* / Q000648:ultrastructure; D020285:Cryoelectron Microscopy; D000458:Cyanobacteria / Q000502:physiology*; D013058:Mass Spectrometry; D008958:Models, Molecular; D055503:Protein Multimerization
chemical_list: D001426:Bacterial Proteins; D056925:Circadian Rhythm Signaling Peptides and Proteins; C114269:KaiA protein, cyanobacteria; C114270:KaiB protein, cyanobacteria; C114271:KaiC protein, cyanobacteria; D000255:Adenosine Triphosphate