Combined SAXS/EM Based Models of the S. elongatus Post-Translational Circadian Oscillator and its Interactions with the Output His-Kinase SasA
| Autor: | Steven Weigand, Martin Egli, Phoebe L. Stewart, Gian Rossi, Rekha Pattanayek, Dewight Williams, Carl Hirschie Johnson, Tetsuya Mori |
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| Rok vydání: | 2011 |
| Předmět: |
Macromolecular Assemblies
Proteomics Anatomy and Physiology Histidine Kinase Protein Conformation Circadian clock Crystallography X-Ray Biochemistry 0302 clinical medicine Protein structure X-Ray Diffraction KaiC KaiA Biomacromolecule-Ligand Interactions Synechococcus 0303 health sciences Multidisciplinary biology Circadian Rhythm Signaling Peptides and Proteins Physics Medicine Research Article Protein Structure Science Protein subunit Biophysics Dephosphorylation 03 medical and health sciences Bacterial Proteins Circadian Clocks Sasa Scattering Small Angle Protein Interaction Domains and Motifs Protein Interactions Biology 030304 developmental biology Binding Sites Phosphotransferases Histidine kinase Proteins biology.organism_classification Microscopy Electron Physiological Processes Chronobiology Protein Kinases 030217 neurology & neurosurgery |
| Zdroj: | PLoS ONE PLoS ONE, Vol 6, Iss 8, p e23697 (2011) |
| ISSN: | 1932-6203 |
| DOI: | 10.1371/journal.pone.0023697 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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