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Li Y, Xu Y. Effects of CikA and SasA co-regulation on cyanobacterial circadian clock. Biosystems 2025; 252:105468. [PMID: 40316194 DOI: 10.1016/j.biosystems.2025.105468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2024] [Revised: 04/11/2025] [Accepted: 04/19/2025] [Indexed: 05/04/2025]
Abstract
Cyanobacterial circadian clock is made up of three proteins, KaiA, KaiB and KaiC. KaiA binds to the A-loop to actives the autophosphorylation of KaiC, while KaiB sequesters KaiA from the A-loop to weaken the activity of KaiA. Thus a circadian oscillator of KaiC phosphorylation generates. Recent experiments have found that CikA and SasA both play crucial roles in cyanobacterial circadian clock. They participate in the output pathway and regulate the activity of transcription factors of the core oscillator. However, the specific impact of the regulation of CikA and SasA on the system is still far from clear. To address these questions, we develop an extended mathematical model for cyanobacterial circadian clock including CikA and SasA regulation. The numerical simulation results indicate that CikA and SasA have opposite effects on the system, and the two complement each other to maintain the balance of the system. Specifically, as the concentration of SasA increases, the period and amplitude increase, and the period sensitivity to parameters, phase shift caused by dark pulses and entrainment ability are all decrease. The regulation of CikA has the opposite impact on the above aspects. Based on these results, we can adjust certain indicators of the system by adjusting the concentration of CikA or SasA. The research method in this article can provide ideas for studying the effects of other proteins on the circadian clock. The findings supplement biological studies and provide a theoretical reference for biological research. It helps us gain a deeper understanding of the dynamic mechanism of cyanobacteria circadian clock.
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Affiliation(s)
- Ying Li
- College of Information Technology, Shanghai Ocean University, Shanghai 201306, China.
| | - Yao Xu
- College of Information Technology, Shanghai Ocean University, Shanghai 201306, China
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2
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Li S, Zhou Z, Wan Y, Jia X, Wang P, Wang Y, Zuo T, Cheng H, Fang X, Dong S, He J, Yang Y, Xu Y, Fu S, Wang X, Qin X, Xie Q, Xu X, Zhao Y, Liang D, Zhang P, Zhang Q, Guo J. Reconstruction of the ancient cyanobacterial proto-circadian clock system KaiABC. EMBO J 2025; 44:3025-3046. [PMID: 40210722 DOI: 10.1038/s44318-025-00425-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2024] [Revised: 02/21/2025] [Accepted: 03/03/2025] [Indexed: 04/12/2025] Open
Abstract
Earlier in its history, the Earth used to spin faster than it does today. How ancient organisms adapted to the short day/night cycles during that time remains unclear. In this study we reconstruct and analyse the ancient circadian clock system KaiABC (anKaiABC) of cyanobacteria that existed ~0.95 billion years ago, when the daily light/dark cycle was ~18 h-long. Compared to their contemporary counterparts, anKaiABC proteins had different structures and interactions. The kinase, phosphatase, and adenosine triphosphatase (ATPase) activities of anKaiC were lower, while the anKaiA and anKaiB proteins were less effective at regulating the KaiC/anKaiC phosphorylation status. We provide evidence indicating that the anKaiABC system does not endogenously oscillate, but it can be entrained by an 18 h-long light/dark cycle. A Synechococcus strain expressing ankaiABC genes exhibits better adaptation to 9-h light/9-h dark cycles (LD9:9) that mimic the ancient 18-h day/night cycles, whereas the kaiABC-expressing strain preferentially adapts to the LD12:12 contemporary conditions. These findings suggest that, despite its lack of self-sustaining circadian oscillation, the proto-circadian system may have mediated adaptation of ancient cyanobacteria to the 18 h-long light/dark cycles present 0.95 billion years ago.
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Affiliation(s)
- Silin Li
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Zengxuan Zhou
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Yufeng Wan
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
- Department of Biology, Texas A&M University, College Station, TX, USA
| | - Xudong Jia
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Peiliang Wang
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Yu Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Taisen Zuo
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
- Spallation Neutron Source Science Center, Dongguan, China
| | - He Cheng
- Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
- Spallation Neutron Source Science Center, Dongguan, China
| | - Xiaoting Fang
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Shuqi Dong
- Center for Biomedical Digital Science, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, GIBH-CUHK Joint Research Laboratory on Stem Cell and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Jun He
- Center for Biomedical Digital Science, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, GIBH-CUHK Joint Research Laboratory on Stem Cell and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
| | - Yilin Yang
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Yichen Xu
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Shaoxuan Fu
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Xujing Wang
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Ximing Qin
- Department of Health Sciences, Institutes of Physical Science and Information Technology, Anhui University, Hefei, China
| | - Qiguang Xie
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Xiaodong Xu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Yuwei Zhao
- School of Life Sciences, Northwest University, Xi'an, China
| | - Dan Liang
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Peng Zhang
- State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory for Aquatic Economic Animals, School of Life Sciences, Sun Yat-Sen University, Guangzhou, China
| | - Qinfen Zhang
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China
| | - Jinhu Guo
- School of Life Sciences, Key Laboratory of Gene Engineering of the Ministry of Education, Sun Yat-sen University, Guangzhou, China.
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Matsukami Y, Oyama K, Azai C, Onoue Y, Fujita Y, Terauchi K. KaiC family ATPases in the nonheterocystous nitrogen-fixing cyanobacterium Leptolyngbya boryana. Sci Rep 2024; 14:30949. [PMID: 39730647 DOI: 10.1038/s41598-024-81991-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2024] [Accepted: 12/02/2024] [Indexed: 12/29/2024] Open
Abstract
A circadian clock is reconstituted in vitro by incubating three proteins, KaiA, KaiB, and KaiC from the non-nitrogen-fixing cyanobacterium Synechococcus elongatus PCC 7942 in the presence of ATP. Leptolyngbya boryana is a filamentous cyanobacterium that grows diazotrophically under microoxic conditions. Among the aforementioned proteins, KaiC is the main clock oscillator belonging to the RecA ATPase superfamily. Genomic studies have revealed the presence of many genes encoding KaiC family ATPases in archaea and bacteria; however, very few have been analyzed in detail. For example, the L. boryana genome encodes two kaiC homologs designated as LbkaiC1 (LBWT_14830) and LbkaiC2 (LBWT_17950). LbKaiC1 is highly similar to KaiC from S. elongatus PCC 7942 compared with LbKaiC2. LbKaiC1 and LbKaiC2 were purified as Strep-tag fusion proteins. LbKaiC1 formed a hexamer and exhibited autophosphorylation, autodephosphorylation, and ATPase activities. Furthermore, it exhibited circadian phosphorylation rhythm in the presence of KaiA and KaiB from S. elongatus PCC 7942, indicating that LbKaiC1 is the central oscillator of the circadian clock in L. boryana. The temporal separation of nitrogen fixation from photosynthesis may be supported by the circadian rhythm generated by LbKaiC1 in L. boryana. LbKaiC2 had low ATPase activity, which depended on temperature, and its autophosphorylation activity was not detected like a circadian oscillator KaiC. Although the function of LbKaiC2 remains unknown, this work will provide comprehensive understanding of KaiC family ATPases.
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Affiliation(s)
- Yusuke Matsukami
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
| | - Katsuaki Oyama
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
| | - Chihiro Azai
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
- Department of Biological Sciences, Faculty of Science and Engineering, Chuo University, Tokyo, 112-8551, Japan
| | - Yasuhiro Onoue
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
- Research Center of Integrative Molecular Systems, Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, 444-8585, Japan
| | - Yuichi Fujita
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Kazuki Terauchi
- Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan.
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4
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Géron A, Werner J, Wattiez R, Matallana-Surget S. Towards the discovery of novel molecular clocks in Prokaryotes. Crit Rev Microbiol 2024; 50:491-503. [PMID: 37330701 DOI: 10.1080/1040841x.2023.2220789] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 01/17/2023] [Accepted: 02/15/2023] [Indexed: 06/19/2023]
Abstract
Diel cycle is of enormous biological importance as it imposes daily oscillation in environmental conditions, which temporally structures most ecosystems. Organisms developed biological time-keeping mechanisms - circadian clocks - that provide a significant fitness advantage over competitors by optimising the synchronisation of their biological activities. While circadian clocks are ubiquitous in Eukaryotes, they are so far only characterised in Cyanobacteria within Prokaryotes. However, growing evidence suggests that circadian clocks are widespread in the bacterial and archaeal domains. As Prokaryotes are at the heart of crucial environmental processes and are essential to human health, unravelling their time-keeping systems provides numerous applications in medical research, environmental sciences, and biotechnology. In this review, we elaborate on how novel circadian clocks in Prokaryotes offer research and development perspectives. We compare and contrast the different circadian systems in Cyanobacteria and discuss about their evolution and taxonomic distribution. We necessarily provide an updated phylogenetic analysis of bacterial and archaeal species that harbour homologs of the main cyanobacterial clock components. Finally, we elaborate on new potential clock-controlled microorganisms that represent opportunities of ecological and industrial relevance in prokaryotic groups such as anoxygenic photosynthetic bacteria, methanogenic archaea, methanotrophs or sulphate-reducing bacteria.
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Affiliation(s)
- Augustin Géron
- Division of Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, UK
- Proteomic and Microbiology Department, University of Mons, Mons, Belgium
| | - Johannes Werner
- High Performance and Cloud Computing Group, Zentrum für Datenverarbeitung (ZDV), University of Tübingen, Tübingen, Germany
| | - Ruddy Wattiez
- Proteomic and Microbiology Department, University of Mons, Mons, Belgium
| | - Sabine Matallana-Surget
- Division of Biological and Environmental Sciences, Faculty of Natural Sciences, University of Stirling, Stirling, UK
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5
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Fang M, LiWang A, Golden SS, Partch CL. The inner workings of an ancient biological clock. Trends Biochem Sci 2024; 49:236-246. [PMID: 38185606 PMCID: PMC10939747 DOI: 10.1016/j.tibs.2023.12.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Revised: 11/30/2023] [Accepted: 12/15/2023] [Indexed: 01/09/2024]
Abstract
Circadian clocks evolved in diverse organisms as an adaptation to the daily swings in ambient light and temperature that derive from Earth's rotation. These timing systems, based on intracellular molecular oscillations, synchronize organisms' behavior and physiology with the 24-h environmental rhythm. The cyanobacterial clock serves as a special model for understanding circadian rhythms because it can be fully reconstituted in vitro. This review summarizes recent advances that leverage new biochemical, biophysical, and mathematical approaches to shed light on the molecular mechanisms of cyanobacterial Kai proteins that support the clock, and their homologues in other bacteria. Many questions remain in circadian biology, and the tools developed for the Kai system will bring us closer to the answers.
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Affiliation(s)
- Mingxu Fang
- Department of Molecular Biology, University of California - San Diego, La Jolla, CA 92093, USA; Center for Circadian Biology, University of California - San Diego, La Jolla, CA 92093, USA
| | - Andy LiWang
- Center for Circadian Biology, University of California - San Diego, La Jolla, CA 92093, USA; Department of Chemistry and Biochemistry, University of California - Merced, Merced, CA 95343, USA; Center for Cellular and Biomolecular Machines, University of California - Merced, Merced, CA 95343, USA
| | - Susan S Golden
- Department of Molecular Biology, University of California - San Diego, La Jolla, CA 92093, USA; Center for Circadian Biology, University of California - San Diego, La Jolla, CA 92093, USA
| | - Carrie L Partch
- Center for Circadian Biology, University of California - San Diego, La Jolla, CA 92093, USA; Department of Chemistry & Biochemistry, University of California - Santa Cruz, Santa Cruz, CA 95064, USA.
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6
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Han X, Zhang D, Hong L, Yu D, Wu Z, Yang T, Rust M, Tu Y, Ouyang Q. Determining subunit-subunit interaction from statistics of cryo-EM images: observation of nearest-neighbor coupling in a circadian clock protein complex. Nat Commun 2023; 14:5907. [PMID: 37737245 PMCID: PMC10516925 DOI: 10.1038/s41467-023-41575-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 09/08/2023] [Indexed: 09/23/2023] Open
Abstract
Biological processes are typically actuated by dynamic multi-subunit molecular complexes. However, interactions between subunits, which govern the functions of these complexes, are hard to measure directly. Here, we develop a general approach combining cryo-EM imaging technology and statistical modeling and apply it to study the hexameric clock protein KaiC in Cyanobacteria. By clustering millions of KaiC monomer images, we identify two major conformational states of KaiC monomers. We then classify the conformational states of (>160,000) KaiC hexamers by the thirteen distinct spatial arrangements of these two subunit states in the hexamer ring. We find that distributions of the thirteen hexamer conformational patterns for two KaiC phosphorylation mutants can be fitted quantitatively by an Ising model, which reveals a significant cooperativity between neighboring subunits with phosphorylation shifting the probability of subunit conformation. Our results show that a KaiC hexamer can respond in a switch-like manner to changes in its phosphorylation level.
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Affiliation(s)
- Xu Han
- State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China
| | - Dongliang Zhang
- State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China
| | - Lu Hong
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL, 60637, USA
| | - Daqi Yu
- State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China
| | - Zhaolong Wu
- State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China
| | - Tian Yang
- State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China
| | - Michael Rust
- Departments of Molecular Genetics and Cell Biology and of Physics, University of Chicago, Chicago, IL, 60637, USA.
| | - Yuhai Tu
- IBM T. J. Watson Research Center, Yorktown Heights, NY, 10598, USA.
| | - Qi Ouyang
- State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, 100871, China.
- Center for Quantitative Biology and Peking-Tsinghua Center for Life Sciences, AAIC, Peking University, Beijing, 100871, China.
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7
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The increasing role of structural proteomics in cyanobacteria. Essays Biochem 2022; 67:269-282. [PMID: 36503929 PMCID: PMC10070481 DOI: 10.1042/ebc20220095] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 11/11/2022] [Accepted: 11/23/2022] [Indexed: 12/14/2022]
Abstract
Abstract
Cyanobacteria, also known as blue–green algae, are ubiquitous organisms on the planet. They contain tremendous protein machineries that are of interest to the biotechnology industry and beyond. Recently, the number of annotated cyanobacterial genomes has expanded, enabling structural studies on known gene-coded proteins to accelerate. This review focuses on the advances in mass spectrometry (MS) that have enabled structural proteomics studies to be performed on the proteins and protein complexes within cyanobacteria. The review also showcases examples whereby MS has revealed critical mechanistic information behind how these remarkable machines within cyanobacteria function.
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8
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Dimer dissociation is a key energetic event in the fold-switch pathway of KaiB. Biophys J 2022; 121:943-955. [PMID: 35151633 PMCID: PMC8943816 DOI: 10.1016/j.bpj.2022.02.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 12/14/2021] [Accepted: 02/09/2022] [Indexed: 11/21/2022] Open
Abstract
Cyanobacteria possesses the simplest circadian clock, composed of three proteins that act as a phosphorylation oscillator: KaiA, KaiB, and KaiC. The timing of this oscillator is determined by the fold-switch of KaiB, a structural rearrangement of its C-terminal half that is accompanied by a change in the oligomerization state. During the day, KaiB forms a stable tetramer (gsKaiB), whereas it adopts a monomeric thioredoxin-like fold during the night (fsKaiB). Although the structures and functions of both native states are well studied, little is known about the sequence and structure determinants that control their structural interconversion. Here, we used confinement molecular dynamics (CCR-MD) and folding simulations using structure-based models to show that the dissociation of the gsKaiB dimer is a key energetic event for the fold-switch. Hydrogen-deuterium exchange mass spectrometry (HDXMS) recapitulates the local stability of protein regions reported by CCR-MD, with both approaches consistently indicating that the energy and backbone flexibility changes are solely associated with the region that fold-switches between gsKaiB and fsKaiB and that the localized regions that differentially stabilize gsKaiB also involve regions outside the dimer interface. Moreover, two mutants (R23C and R75C) previously reported to be relevant for altering the rhythmicity of the Kai clock were also studied by HDXMS. Particularly, R75C populates dimeric and monomeric states with a deuterium incorporation profile comparable to the one observed for fsKaiB, emphasizing the importance of the oligomerization state of KaiB for the fold-switch. These findings suggest that the information necessary to control the rhythmicity of the cyanobacterial biological clock is, to a great extent, encoded within the KaiB sequence.
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de Sousa Machado JN, Vollmar L, Schimpf J, Chaudhury P, Kumariya R, van der Does C, Hugel T, Albers SV. Autophosphorylation of the KaiC-like protein ArlH inhibits oligomerization and interaction with ArlI, the motor ATPase of the archaellum. Mol Microbiol 2021; 116:943-956. [PMID: 34219289 DOI: 10.1111/mmi.14781] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/02/2021] [Accepted: 07/02/2021] [Indexed: 12/27/2022]
Abstract
Motile archaea are propelled by the archaellum, whose motor complex consists of the membrane protein ArlJ, the ATPase ArlI, and the ATP-binding protein ArlH. Despite its essential function and the existence of structural and biochemical data on ArlH, the role of ArlH in archaellum assembly and function remains elusive. ArlH is a structural homolog of KaiC, the central component of the cyanobacterial circadian clock. Since autophosphorylation and dephosphorylation of KaiC are central properties for the function of KaiC, we asked whether autophosphorylation is also a property of ArlH proteins. We observed that both ArlH from the euryarchaeon Pyrococcus furiosus (PfArlH) and from the crenarchaeon Sulfolobus acidocaldarius (SaArlH) have autophosphorylation activity. Using a combination of single-molecule fluorescence measurements and biochemical assays, we show that autophosphorylation of ArlH is closely linked to its oligomeric state when bound to hexameric ArlI. These experiments also strongly suggest that ArlH is a hexamer in its ArlI-bound state. Mutagenesis of the putative catalytic residue (Glu-57 in SaArlH) in ArlH results in a reduced autophosphorylation activity and abolished archaellation and motility in S. acidocaldarius, indicating that optimum phosphorylation activity of ArlH is essential for archaellation and motility.
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Affiliation(s)
- J Nuno de Sousa Machado
- Molecular Biology of Archaea and Signaling Research Centre BIOSS, Institute of Biology II, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Spemann Graduate School of Biology and Medicine, University of Freiburg, Freiburg, Germany
| | - Leonie Vollmar
- Spemann Graduate School of Biology and Medicine, University of Freiburg, Freiburg, Germany.,Institute of Physical Chemistry and Signaling Research Centers BIOSS and CIBSS, University of Freiburg, Freiburg, Germany
| | - Julia Schimpf
- Spemann Graduate School of Biology and Medicine, University of Freiburg, Freiburg, Germany.,Institute of Physical Chemistry and Signaling Research Centers BIOSS and CIBSS, University of Freiburg, Freiburg, Germany
| | - Paushali Chaudhury
- Molecular Biology of Archaea and Signaling Research Centre BIOSS, Institute of Biology II, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Rashmi Kumariya
- Molecular Biology of Archaea and Signaling Research Centre BIOSS, Institute of Biology II, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Chris van der Does
- Molecular Biology of Archaea and Signaling Research Centre BIOSS, Institute of Biology II, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Thorsten Hugel
- Institute of Physical Chemistry and Signaling Research Centers BIOSS and CIBSS, University of Freiburg, Freiburg, Germany
| | - Sonja-Verena Albers
- Molecular Biology of Archaea and Signaling Research Centre BIOSS, Institute of Biology II, Faculty of Biology, University of Freiburg, Freiburg, Germany
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10
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Palm D, Uzoni A, Simon F, Fischer M, Coogan A, Tucha O, Thome J, Faltraco F. Evolutionary conservations, changes of circadian rhythms and their effect on circadian disturbances and therapeutic approaches. Neurosci Biobehav Rev 2021; 128:21-34. [PMID: 34102148 DOI: 10.1016/j.neubiorev.2021.06.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 02/04/2021] [Accepted: 06/01/2021] [Indexed: 12/21/2022]
Abstract
The circadian rhythm is essential for the interaction of all living organisms with their environments. Several processes, such as thermoregulation, metabolism, cognition and memory, are regulated by the internal clock. Disturbances in the circadian rhythm have been shown to lead to the development of neuropsychiatric disorders, including attention-deficit hyperactivity disorder (ADHD). Interestingly, the mechanism of the circadian rhythms has been conserved in many different species, and misalignment between circadian rhythms and the environment results in evolutionary regression and lifespan reduction. This review summarises the conserved mechanism of the internal clock and its major interspecies differences. In addition, it focuses on effects the circadian rhythm disturbances, especially in cases of ADHD, and describes the possibility of recombinant proteins generated by eukaryotic expression systems as therapeutic agents as well as CRISPR/Cas9 technology as a potential tool for research and therapy. The aim is to give an overview about the evolutionary conserved mechanism as well as the changes of the circadian clock. Furthermore, current knowledge about circadian rhythm disturbances and therapeutic approaches is discussed.
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Affiliation(s)
- Denise Palm
- Department of Psychiatry and Psychotherapy, University Medical Center Rostock, Rostock, Gehlsheimer Str. 20, 18147, Rostock, Germany
| | - Adriana Uzoni
- Department of Psychiatry and Psychotherapy, University Medical Center Rostock, Rostock, Gehlsheimer Str. 20, 18147, Rostock, Germany
| | - Frederick Simon
- Department of Psychiatry and Psychotherapy, University Medical Center Rostock, Rostock, Gehlsheimer Str. 20, 18147, Rostock, Germany
| | - Matthias Fischer
- Department of Psychiatry and Psychotherapy, University Medical Center Rostock, Rostock, Gehlsheimer Str. 20, 18147, Rostock, Germany
| | - Andrew Coogan
- Department of Psychology, Maynooth University, National University of Ireland, Ireland
| | - Oliver Tucha
- Department of Psychiatry and Psychotherapy, University Medical Center Rostock, Rostock, Gehlsheimer Str. 20, 18147, Rostock, Germany
| | - Johannes Thome
- Department of Psychiatry and Psychotherapy, University Medical Center Rostock, Rostock, Gehlsheimer Str. 20, 18147, Rostock, Germany
| | - Frank Faltraco
- Department of Psychiatry and Psychotherapy, University Medical Center Rostock, Rostock, Gehlsheimer Str. 20, 18147, Rostock, Germany.
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11
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de Sousa Machado JN, Vollmar L, Schimpf J, Chaudhury P, Kumariya R, van der Does C, Hugel T, Albers S. Autophosphorylation of the KaiC-like protein ArlH inhibits oligomerisation and interaction with ArlI, the motor ATPase of the archaellum.. [DOI: 10.1101/2021.03.19.436134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2023]
Abstract
Motile archaea are propelled by the archaellum, whose motor complex consists of the membrane protein ArlJ, the ATPase ArlI, and the ATP-binding protein ArlH. Despite its essential function and the existence of structural and biochemical data on ArlH, the role of ArlH in archaellum assembly and function remains elusive. ArlH is a structural homolog of KaiC, the central component of the cyanobacterial circadian clock. Similar to KaiC, ArlH exhibits autophosphorylation activity, which was observed for both ArlH of the euryarchaeonPyrococcus furiosus (PfArlH)and the crenarchaeonSulfolobus acidocaldarius(SaArlH). Using a combination of single molecule fluorescence measurements and biochemical assays, it is shown that autophosphorylation of ArlH is closely linked to the oligomeric state of ArlH bound to ArlI. These experiments also strongly suggest that ArlH is a hexamer in its functional ArlI bound state. Mutagenesis of the putative catalytic residue Glu-57 inSaArlH results in a reduced autophosphorylation activity and abolished archaellation and motility, suggesting that optimum phosphorylation activity of ArlH is essential for both archaellation and motility.
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12
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Mutoh R, Iwata K, Iida T, Ishiura M, Onai K. Rhythmic adenosine triphosphate release from the cyanobacterial circadian clock protein KaiC revealed by real-time monitoring of bioluminescence using firefly luciferase. Genes Cells 2021; 26:83-93. [PMID: 33341998 DOI: 10.1111/gtc.12825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 12/16/2020] [Accepted: 12/16/2020] [Indexed: 11/27/2022]
Abstract
The cyanobacterial circadian clock is composed of three clock proteins, KaiA, KaiB and KaiC. This KaiABC clock system can be reconstituted in vitro in the presence of adenosine triphosphate (ATP) and Mg2+ , and shows circadian rhythms in the phosphorylation level and ATPase activity of KaiC. Previously, we found that ATP regulates a complex formation between KaiB and KaiC, and KaiC releases ATP from KaiC itself (PLoS One, 8, 2013, e80200). In this study, we examined whether the ATP release from KaiC shows any rhythms in vitro. We monitored the release of ATP from wild-type and ATPase motif mutants of KaiC as a bioluminescence in real time using a firefly luciferase assay in vitro and obtained the following results: (a) ATP release from KaiC oscillated even without KaiA and KaiB although period of the oscillation was not 24 hr; (b) ATP was mainly released from the N-terminal domain of KaiC; and (c) the ATP release was enhanced and suppressed by KaiB and KaiA, respectively. These results suggest that KaiC can generate basal oscillation as a core clock without KaiA and KaiB, whereas these two proteins contribute to adjusting and stabilizing the oscillation.
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Affiliation(s)
- Risa Mutoh
- Center for Gene Research, Nagoya University, Nagoya, Japan
| | - Keita Iwata
- Center for Gene Research, Nagoya University, Nagoya, Japan.,Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Takahiro Iida
- Center for Gene Research, Nagoya University, Nagoya, Japan
| | - Masahiro Ishiura
- Center for Gene Research, Nagoya University, Nagoya, Japan.,Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Kiyoshi Onai
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
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13
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Involvement of glycogen metabolism in circadian control of UV resistance in cyanobacteria. PLoS Genet 2020; 16:e1009230. [PMID: 33253146 PMCID: PMC7728383 DOI: 10.1371/journal.pgen.1009230] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 12/10/2020] [Accepted: 10/28/2020] [Indexed: 11/30/2022] Open
Abstract
Most organisms harbor circadian clocks as endogenous timing systems in order to adapt to daily environmental changes, such as exposure to ultraviolet (UV) light. It has been hypothesized that the circadian clock evolved to prevent UV-sensitive activities, such as DNA replication and cell division, during the daytime. Indeed, circadian control of UV resistance has been reported in several eukaryotic organisms, from algae to higher organisms, although the underlying mechanisms remain unknown. Here, we demonstrate that the unicellular cyanobacterium Synechococcus elongatus PCC 7942 exhibits a circadian rhythm in resistance to UV-C and UV-B light, which is higher during subjective dawn and lower during subjective dusk. Nullification of the clock gene cluster kaiABC or the DNA-photolyase phr abolished rhythmicity with constitutively lower resistance to UV-C light, and amino acid substitutions of KaiC altered the period lengths of the UV-C resistance rhythm. In order to elucidate the molecular mechanism underlying the circadian regulation of UV-C resistance, transposon insertion mutants that alter UV-C resistance were isolated. Mutations to the master circadian output mediator genes sasA and rpaA and the glycogen degradation enzyme gene glgP abolished circadian rhythms of UV-C resistance with constitutively high UV-C resistance. Combining these results with further experiments using ATP synthesis inhibitor and strains with modified metabolic pathways, we showed that UV-C resistance is weakened by directing more metabolic flux from the glycogen degradation to catabolic pathway such as oxidative pentose phosphate pathway and glycolysis. We suggest glycogen-related metabolism in the dark affects circadian control in UV sensitivity, while the light masks this effect through the photolyase function. Most organisms harbor circadian clocks to adapt to daily environmental changes. It has been hypothesized that adaptation to UV radiation during the day was a driving force of the evolution of the circadian clock (known as “the flight from light” hypothesis). Thus, understanding the relationship with UV resistance is important to consider the physiological relevance and an evolutionary origin of the circadian clock. We here demonstrate that the unicellular cyanobacterium, Synechococcus elongatus exhibits a circadian rhythm in resistance to UV-C light, which is higher and lower during subjective dawn and dusk, respectively. This rhythm was abolished by nullification of the clock gene cluster kaiABC, and the period length was changed consistently by period mutations on kaiC. Genetic screening revealed that nullification of clock-associating genes sasA, cikA and rpaA, and of a glycogen degradation enzyme gene glgP abolished or attenuated the UV-resistance rhythm. Combining these results with further experiments using an ATP synthesis inhibitor and strains with modified metabolic pathways, we suggest a that the circadian clock confers adaptive fitness by balancing a trade-off between glycogen-related energy metabolism and the UV-resistance property.
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14
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Kawamoto N, Ito H, Tokuda IT, Iwasaki H. Damped circadian oscillation in the absence of KaiA in Synechococcus. Nat Commun 2020; 11:2242. [PMID: 32382052 PMCID: PMC7205874 DOI: 10.1038/s41467-020-16087-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Accepted: 04/09/2020] [Indexed: 01/05/2023] Open
Abstract
Proteins KaiA, KaiB and KaiC constitute a biochemical circadian oscillator in the cyanobacterium Synechococcus elongatus. It has been reported kaiA inactivation completely abolishes circadian oscillations. However, we show here that kaiBC promoter activity exhibits a damped, low-amplitude oscillation with a period of approximately 24 h in kaiA-inactivated strains. The damped rhythm resonates with external cycles with a period of 24–26 h, indicating that its natural frequency is similar to that of the circadian clock. Double-mutation experiments reveal that kaiC, kaiB, and sasA (encoding a KaiC-binding histidine kinase) are all required for the damped oscillation. Further analysis suggests that the kaiA-less damped transcriptional rhythm requires KaiB-KaiC complex formation and the transcription-translation feedback loop, but not the KaiC phosphorylation cycle. Our results provide insights into mechanisms that could potentially underlie the diurnal/circadian behaviors observed in other bacterial species that possess kaiB and kaiC homologues but lack a kaiA homologue. Proteins KaiA, KaiB and KaiC constitute a biochemical circadian oscillator in Synechococcus cyanobacteria. Here, Kawamoto et al. show that kaiBC promoter activity exhibits a damped, low-amplitude circadian oscillation in the absence of KaiA, which could explain the circadian rhythms observed in other bacteria that lack a kaiA homologue.
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Affiliation(s)
- Naohiro Kawamoto
- Department of Electrical Engineering and Biological Science, Waseda University, Tokyo, 162-0056, Japan
| | - Hiroshi Ito
- Faculty of Design, Kyushu University, Fukuoka, 815-8540, Japan
| | - Isao T Tokuda
- Graduate School of Science and Engineering, Ritsumeikan University, Shiga, 525-8577, Japan
| | - Hideo Iwasaki
- Department of Electrical Engineering and Biological Science, Waseda University, Tokyo, 162-0056, Japan.
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15
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Synechocystis KaiC3 Displays Temperature- and KaiB-Dependent ATPase Activity and Is Important for Growth in Darkness. J Bacteriol 2020; 202:JB.00478-19. [PMID: 31767776 PMCID: PMC6989803 DOI: 10.1128/jb.00478-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 11/17/2019] [Indexed: 02/05/2023] Open
Abstract
Cyanobacteria form a heterogeneous bacterial group with diverse lifestyles, acclimation strategies, and differences in the presence of circadian clock proteins. In Synechococcus elongatus PCC 7942, a unique posttranslational KaiABC oscillator drives circadian rhythms. ATPase activity of KaiC correlates with the period of the clock and mediates temperature compensation. Synechocystis sp. strain PCC 6803 expresses additional Kai proteins, of which KaiB3 and KaiC3 proteins were suggested to fine-tune the standard KaiAB1C1 oscillator. In the present study, we therefore characterized the enzymatic activity of KaiC3 as a representative of nonstandard KaiC homologs in vitro KaiC3 displayed ATPase activity lower than that of the Synechococcus elongatus PCC 7942 KaiC protein. ATP hydrolysis was temperature dependent. Hence, KaiC3 is missing a defining feature of the model cyanobacterial circadian oscillator. Yeast two-hybrid analysis showed that KaiC3 interacts with KaiB3, KaiC1, and KaiB1. Further, KaiB3 and KaiB1 reduced in vitro ATP hydrolysis by KaiC3. Spot assays showed that chemoheterotrophic growth in constant darkness is completely abolished after deletion of ΔkaiAB1C1 and reduced in the absence of kaiC3 We therefore suggest a role for adaptation to darkness for KaiC3 as well as a cross talk between the KaiC1- and KaiC3-based systems.IMPORTANCE The circadian clock influences the cyanobacterial metabolism, and deeper understanding of its regulation will be important for metabolic optimizations in the context of industrial applications. Due to the heterogeneity of cyanobacteria, characterization of clock systems in organisms apart from the circadian model Synechococcus elongatus PCC 7942 is required. Synechocystis sp. strain PCC 6803 represents a major cyanobacterial model organism and harbors phylogenetically diverged homologs of the clock proteins, which are present in various other noncyanobacterial prokaryotes. By our in vitro studies we unravel the interplay of the multiple Synechocystis Kai proteins and characterize enzymatic activities of the nonstandard clock homolog KaiC3. We show that the deletion of kaiC3 affects growth in constant darkness, suggesting its involvement in the regulation of nonphotosynthetic metabolic pathways.
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16
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Tarrant AM, Helm RR, Levy O, Rivera HE. Environmental entrainment demonstrates natural circadian rhythmicity in the cnidarian Nematostella vectensis. ACTA ACUST UNITED AC 2019; 222:jeb.205393. [PMID: 31611292 DOI: 10.1242/jeb.205393] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 10/10/2019] [Indexed: 12/21/2022]
Abstract
Considerable advances in chronobiology have been made through controlled laboratory studies, but distinct temporal rhythms can emerge under natural environmental conditions. Lab-reared Nematostella vectensis sea anemones exhibit circadian behavioral and physiological rhythms. Given that these anemones inhabit shallow estuarine environments subject to tidal inputs, it was unclear whether circadian rhythmicity would persist following entrainment in natural conditions, or whether circatidal periodicity would predominate. Nematostella were conditioned within a marsh environment, where they experienced strong daily temperature cycles as well as brief tidal flooding around the full and new moons. Upon retrieval, anemones exhibited strong circadian (∼24 h) activity rhythms under a light-dark cycle or continuous darkness, but reduced circadian rhythmicity under continuous light. However, some individuals in each light condition showed circadian rhythmicity, and a few individuals showed circatidal rhythmicity. Consistent with the behavioral studies, a large number of transcripts (1640) exhibited diurnal rhythmicity compared with very few (64) with semidiurnal rhythmicity. Diurnal transcripts included core circadian regulators, and 101 of 434 (23%) genes that were previously found to be upregulated by exposure to ultraviolet radiation. Together, these behavioral and transcriptional studies show that circadian rhythmicity predominates and suggest that solar radiation drives physiological cycles in this sediment-dwelling subtidal animal.
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Affiliation(s)
- Ann M Tarrant
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543, USA
| | - Rebecca R Helm
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543, USA.,Biology Department, University of North Carolina Asheville, Asheville NC 28804, USA
| | - Oren Levy
- Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Hanny E Rivera
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole MA 02543, USA.,Biology Department, Boston University, Boston MA 02215, USA
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17
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Abstract
Circadian oscillators are networks of biochemical feedback loops that generate 24-hour rhythms in organisms from bacteria to animals. These periodic rhythms result from a complex interplay among clock components that are specific to the organism, but share molecular mechanisms across kingdoms. A full understanding of these processes requires detailed knowledge, not only of the biochemical properties of clock proteins and their interactions, but also of the three-dimensional structure of clockwork components. Posttranslational modifications and protein–protein interactions have become a recent focus, in particular the complex interactions mediated by the phosphorylation of clock proteins and the formation of multimeric protein complexes that regulate clock genes at transcriptional and translational levels. This review covers the structural aspects of circadian oscillators, and serves as a primer for this exciting realm of structural biology.
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Affiliation(s)
- Reena Saini
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.,Max-Planck-Institut für Pflanzenzüchtungsforschung, Cologne, Germany
| | - Mariusz Jaskolski
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.,Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland
| | - Seth J Davis
- Max-Planck-Institut für Pflanzenzüchtungsforschung, Cologne, Germany. .,Department of Biology, University of York, York, UK.
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18
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Abstract
Life has adapted to Earth's day-night cycle with the evolution of endogenous biological clocks. Whereas these circadian rhythms typically involve extensive transcription-translation feedback in higher organisms, cyanobacteria have a circadian clock, which functions primarily as a protein-based post-translational oscillator. Known as the Kai system, it consists of three proteins KaiA, KaiB, and KaiC. In this chapter, we provide a detailed structural overview of the Kai components and how they interact to produce circadian rhythms of global gene expression in cyanobacterial cells. We discuss how the circadian oscillation is coupled to gene expression, intertwined with transcription-translation feedback mechanisms, and entrained by input from the environment. We discuss the use of mathematical models and summarize insights into the cyanobacterial circadian clock from theoretical studies. The molecular details of the Kai system are well documented for the model cyanobacterium Synechococcus elongatus, but many less understood varieties of the Kai system exist across the highly diverse phylum of Cyanobacteria. Several species contain multiple kai-gene copies, while others like marine Prochlorococcus strains have a reduced kaiBC-only system, lacking kaiA. We highlight recent findings on the genomic distribution of kai genes in Bacteria and Archaea and finally discuss hypotheses on the evolution of the Kai system.
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Affiliation(s)
- Joost Snijder
- Snijder Bioscience, Zevenwouden 143, 3524CN, Utrecht, The Netherlands
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Ilka Maria Axmann
- Synthetic Microbiology, Biology Department, Heinrich Heine University Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany.
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19
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Abstract
Mounting evidence in recent years supports the extensive interaction between the circadian and redox systems. The existence of such a relationship is not surprising because most organisms, be they diurnal or nocturnal, display daily oscillations in energy intake, locomotor activity, and exposure to exogenous and internally generated oxidants. The transcriptional clock controls the levels of many antioxidant proteins and redox-active cofactors, and, conversely, the cellular redox poise has been shown to feed back to the transcriptional oscillator via redox-sensitive transcription factors and enzymes. However, the circadian cycles in the S-sulfinylation of the peroxiredoxin (PRDX) proteins constituted the first example of an autonomous circadian redox oscillation, which occurred independently of the transcriptional clock. Importantly, the high phylogenetic conservation of these rhythms suggests that they might predate the evolution of the transcriptional oscillator, and therefore could be a part of a primordial circadian redox/metabolic oscillator. This discovery forced the reappraisal of the dogmatic transcription-centered view of the clockwork and opened a new avenue of research. Indeed, the investigation into the links between the circadian and redox systems is still in its infancy, and many important questions remain to be addressed.
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20
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Egli M. Architecture and mechanism of the central gear in an ancient molecular timer. J R Soc Interface 2017; 14:rsif.2016.1065. [PMID: 28330987 DOI: 10.1098/rsif.2016.1065] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Accepted: 02/27/2017] [Indexed: 12/16/2022] Open
Abstract
Molecular clocks are the product of natural selection in organisms from bacteria to human and their appearance early in evolution such as in the prokaryotic cyanobacterium Synechococcus elongatus suggests that these timers served a crucial role in genetic fitness. Thus, a clock allows cyanobacteria relying on photosynthesis and nitrogen fixation to temporally space the two processes and avoid exposure of nitrogenase carrying out fixation to high levels of oxygen produced during photosynthesis. Fascinating properties of molecular clocks are the long time constant, their precision and temperature compensation. Although these are hallmarks of all circadian oscillators, the actual cogs and gears that control clocks vary widely between organisms, indicating that circadian timers evolved convergently multiple times, owing to the selective pressure of an environment with a daily light/dark cycle. In S. elongatus, the three proteins KaiA, KaiB and KaiC in the presence of ATP constitute a so-called post-translational oscillator (PTO). The KaiABC PTO can be reconstituted in an Eppendorf tube and keeps time in a temperature-compensated manner. The ease by which the KaiABC clock can be studied in vitro has made it the best-investigated molecular clock system. Over the last decade, structures of all three Kai proteins and some of their complexes have emerged and mechanistic aspects have been analysed in considerable detail. This review focuses on the central gear of the S. elongatus clock and only enzyme among the three proteins: KaiC. Our determination of the three-dimensional structure of KaiC early in the quest for a better understanding of the inner workings of the cyanobacterial timer revealed its unusual architecture and conformational differences and unique features of the two RecA-like domains constituting KaiC. The structure also pinpointed phosphorylation sites and differential interactions with ATP molecules at subunit interfaces, and helped guide experiments to ferret out mechanistic aspects of the ATPase, auto-phosphorylation and auto-dephosphorylation reactions catalysed by the homo-hexamer. Comparisons between the structure of KaiC and those of nanomachines such as F1-ATPase and CaMKII also exposed shared architectural features (KaiC/ATPase), mechanistic principles (KaiC/CaMKII) and phenomena, such as subunit exchange between hexameric particles critical for function (clock synchronization, KaiABC; memory-storage, CaMKII).
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Affiliation(s)
- Martin Egli
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, USA
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21
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Schmelling NM, Lehmann R, Chaudhury P, Beck C, Albers SV, Axmann IM, Wiegard A. Minimal tool set for a prokaryotic circadian clock. BMC Evol Biol 2017; 17:169. [PMID: 28732467 PMCID: PMC5520375 DOI: 10.1186/s12862-017-0999-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 06/15/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Circadian clocks are found in organisms of almost all domains including photosynthetic Cyanobacteria, whereby large diversity exists within the protein components involved. In the model cyanobacterium Synechococcus elongatus PCC 7942 circadian rhythms are driven by a unique KaiABC protein clock, which is embedded in a network of input and output factors. Homologous proteins to the KaiABC clock have been observed in Bacteria and Archaea, where evidence for circadian behavior in these domains is accumulating. However, interaction and function of non-cyanobacterial Kai-proteins as well as homologous input and output components remain mainly unclear. RESULTS Using a universal BLAST analyses, we identified putative KaiC-based timing systems in organisms outside as well as variations within Cyanobacteria. A systematic analyses of publicly available microarray data elucidated interesting variations in circadian gene expression between different cyanobacterial strains, which might be correlated to the diversity of genome encoded clock components. Based on statistical analyses of co-occurrences of the clock components homologous to Synechococcus elongatus PCC 7942, we propose putative networks of reduced and fully functional clock systems. Further, we studied KaiC sequence conservation to determine functionally important regions of diverged KaiC homologs. Biochemical characterization of exemplary cyanobacterial KaiC proteins as well as homologs from two thermophilic Archaea demonstrated that kinase activity is always present. However, a KaiA-mediated phosphorylation is only detectable in KaiC1 orthologs. CONCLUSION Our analysis of 11,264 genomes clearly demonstrates that components of the Synechococcus elongatus PCC 7942 circadian clock are present in Bacteria and Archaea. However, all components are less abundant in other organisms than Cyanobacteria and KaiA, Pex, LdpA, and CdpA are only present in the latter. Thus, only reduced KaiBC-based or even simpler, solely KaiC-based timing systems might exist outside of the cyanobacterial phylum, which might be capable of driving diurnal oscillations.
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Affiliation(s)
- Nicolas M. Schmelling
- Institute for Synthetic Microbiology, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, Duesseldorf, 40225 Germany
| | - Robert Lehmann
- Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstrasse 43, Berlin, 10115 Germany
| | - Paushali Chaudhury
- Molecular Biology of Archaea, Albert-Ludwigs-University Freiburg, Institute of Biology II, Schaenzlestrasse 1, Freiburg, 79104 Germany
| | - Christian Beck
- Institute for Theoretical Biology, Humboldt University Berlin, Invalidenstrasse 43, Berlin, 10115 Germany
| | - Sonja-Verena Albers
- Molecular Biology of Archaea, Albert-Ludwigs-University Freiburg, Institute of Biology II, Schaenzlestrasse 1, Freiburg, 79104 Germany
| | - Ilka M. Axmann
- Institute for Synthetic Microbiology, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, Duesseldorf, 40225 Germany
| | - Anika Wiegard
- Institute for Synthetic Microbiology, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Duesseldorf, Universitaetsstrasse 1, Duesseldorf, 40225 Germany
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22
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Tseng R, Goularte NF, Chavan A, Luu J, Cohen SE, Chang YG, Heisler J, Li S, Michael AK, Tripathi S, Golden SS, LiWang A, Partch CL. Structural basis of the day-night transition in a bacterial circadian clock. Science 2017; 355:1174-1180. [PMID: 28302851 PMCID: PMC5441561 DOI: 10.1126/science.aag2516] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2016] [Accepted: 02/13/2017] [Indexed: 12/14/2022]
Abstract
Circadian clocks are ubiquitous timing systems that induce rhythms of biological activities in synchrony with night and day. In cyanobacteria, timing is generated by a posttranslational clock consisting of KaiA, KaiB, and KaiC proteins and a set of output signaling proteins, SasA and CikA, which transduce this rhythm to control gene expression. Here, we describe crystal and nuclear magnetic resonance structures of KaiB-KaiC,KaiA-KaiB-KaiC, and CikA-KaiB complexes. They reveal how the metamorphic properties of KaiB, a protein that adopts two distinct folds, and the post-adenosine triphosphate hydrolysis state of KaiC create a hub around which nighttime signaling events revolve, including inactivation of KaiA and reciprocal regulation of the mutually antagonistic signaling proteins, SasA and CikA.
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Affiliation(s)
- Roger Tseng
- Quantitative and Systems Biology, University of California, Merced, CA 95343, USA
| | - Nicolette F Goularte
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
| | - Archana Chavan
- School of Natural Sciences, University of California, Merced, CA 95343, USA
| | - Jansen Luu
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
| | - Susan E Cohen
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Yong-Gang Chang
- School of Natural Sciences, University of California, Merced, CA 95343, USA
| | - Joel Heisler
- Chemistry and Chemical Biology, University of California, Merced, CA 95343, USA
| | - Sheng Li
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Alicia K Michael
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
| | - Sarvind Tripathi
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
| | - Susan S Golden
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Andy LiWang
- Quantitative and Systems Biology, University of California, Merced, CA 95343, USA.
- School of Natural Sciences, University of California, Merced, CA 95343, USA
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
- Chemistry and Chemical Biology, University of California, Merced, CA 95343, USA
- Health Sciences Research Institute, University of California, Merced, CA 95343, USA
| | - Carrie L Partch
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA.
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
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23
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Paijmans J, Lubensky DK, ten Wolde PR. A thermodynamically consistent model of the post-translational Kai circadian clock. PLoS Comput Biol 2017; 13:e1005415. [PMID: 28296888 PMCID: PMC5371392 DOI: 10.1371/journal.pcbi.1005415] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 03/29/2017] [Accepted: 02/15/2017] [Indexed: 11/18/2022] Open
Abstract
The principal pacemaker of the circadian clock of the cyanobacterium S. elongatus is a protein phosphorylation cycle consisting of three proteins, KaiA, KaiB and KaiC. KaiC forms a homohexamer, with each monomer consisting of two domains, CI and CII. Both domains can bind and hydrolyze ATP, but only the CII domain can be phosphorylated, at two residues, in a well-defined sequence. While this system has been studied extensively, how the clock is driven thermodynamically has remained elusive. Inspired by recent experimental observations and building on ideas from previous mathematical models, we present a new, thermodynamically consistent, statistical-mechanical model of the clock. At its heart are two main ideas: i) ATP hydrolysis in the CI domain provides the thermodynamic driving force for the clock, switching KaiC between an active conformational state in which its phosphorylation level tends to rise and an inactive one in which it tends to fall; ii) phosphorylation of the CII domain provides the timer for the hydrolysis in the CI domain. The model also naturally explains how KaiA, by acting as a nucleotide exchange factor, can stimulate phosphorylation of KaiC, and how the differential affinity of KaiA for the different KaiC phosphoforms generates the characteristic temporal order of KaiC phosphorylation. As the phosphorylation level in the CII domain rises, the release of ADP from CI slows down, making the inactive conformational state of KaiC more stable. In the inactive state, KaiC binds KaiB, which not only stabilizes this state further, but also leads to the sequestration of KaiA, and hence to KaiC dephosphorylation. Using a dedicated kinetic Monte Carlo algorithm, which makes it possible to efficiently simulate this system consisting of more than a billion reactions, we show that the model can describe a wealth of experimental data. Circadian clocks are biological timekeeping devices with a rhythm of 24 hours in living cells pertaining to all kingdoms of life. They help organisms to coordinate their behavior with the day-night cycle. The circadian clock of the cyanobacterium Synechococcus elongatus is one of the simplest and best characterized clocks in biology. The central clock component is the protein KaiC, which is phosphorylated and dephosphorylated in a cyclical manner with a 24 hr period. While we know from elementary thermodynamics that oscillations require a net turnover of fuel molecules, in this case ATP, how ATP hydrolysis drives the clock has remained elusive. Based on recent experimental observations and building on ideas from existing models, we construct the most detailed mathematical model of this system to date. KaiC consists of two domains, CI and CII, which each can bind ATP, yet only CII can be phosphorylated. Moreover, KaiC can exist in two conformational states, an active one in which the phosphorylation level tends to rise, and an inactive one in which it tends to fall. Our model predicts that ATP hydrolysis in the CI domain is the principal energetic driver of the clock, driving the switching between the two conformational states, while phosphorylation in the CII domain provides the timer for the conformational switch. The coupling between ATP hydrolysis in the CI domain and phosphorylation in the CII domain leads to novel testable predictions.
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Affiliation(s)
| | - David K. Lubensky
- Department of Physics, University of Michigan, Ann Arbor, Michigan, United States of America
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Millius A, Ueda HR. Systems Biology-Derived Discoveries of Intrinsic Clocks. Front Neurol 2017; 8:25. [PMID: 28220104 PMCID: PMC5292584 DOI: 10.3389/fneur.2017.00025] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 01/17/2017] [Indexed: 12/19/2022] Open
Abstract
A systems approach to studying biology uses a variety of mathematical, computational, and engineering tools to holistically understand and model properties of cells, tissues, and organisms. Building from early biochemical, genetic, and physiological studies, systems biology became established through the development of genome-wide methods, high-throughput procedures, modern computational processing power, and bioinformatics. Here, we highlight a variety of systems approaches to the study of biological rhythms that occur with a 24-h period-circadian rhythms. We review how systems methods have helped to elucidate complex behaviors of the circadian clock including temperature compensation, rhythmicity, and robustness. Finally, we explain the contribution of systems biology to the transcription-translation feedback loop and posttranslational oscillator models of circadian rhythms and describe new technologies and "-omics" approaches to understand circadian timekeeping and neurophysiology.
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Affiliation(s)
- Arthur Millius
- Laboratory for Synthetic Biology, RIKEN Quantitative Biology Center, Suita, Osaka, Japan
| | - Hiroki R. Ueda
- Laboratory for Synthetic Biology, RIKEN Quantitative Biology Center, Suita, Osaka, Japan
- Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
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Bayramov SK. Mathematical Model of Self-Oscillations of Activity of Kai Proteins. BIOCHEMISTRY (MOSCOW) 2017; 81:284-8. [PMID: 27262198 DOI: 10.1134/s0006297916030111] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A non-autocatalytic mathematical model of self-oscillations in vitro in solutions of cyanobacterial Kai proteins (KaiA, KaiB, KaiC) and ATP is suggested. This model describes the process of phosphorylation/dephosphorylation of KaiC protein, which is accelerated by KaiA and inhibited by KaiB. The method of metabolic control analysis is used to show that frequency (period) as well as amplitude of self-oscillations of components of Kai proteins are temperature-compensated.
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Affiliation(s)
- Sh K Bayramov
- Azerbaijan Medical University, Baku, AZ1022, Azerbaijan.
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Schmelling NM, Lehmann R, Chaudhury P, Beck C, Albers SV, Axmann IM, Wiegard A. Minimal Tool Set for a Prokaryotic Circadian Clock.. [DOI: 10.1101/075291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/19/2023]
Abstract
AbstractBackgroundCircadian clocks are found in organisms of almost all domains including photosynthetic Cyanobacteria, whereby large diversity exists within the protein components involved. In the model cyanobacteriumSynechococcus elongatusPCC 7942 circadian rhythms are driven by a unique KaiABC protein clock, which is embedded in a network of input and output factors. Homologous proteins to the KaiABC clock have been observed in Bacteria and Archaea, where evidence for circadian behavior in these domains is accumulating. However, interaction and function of non-cyanobacterial Kai-proteins as well as homologous input and output components remain mainly unclear.ResultsUsing a universal BLAST analyses, we identified putative KaiC-based timing systems in organisms outside as well as variations within Cyanobacteria. A systematic analyses of publicly available microarray data elucidated interesting variations in circadian gene expression between different cyanobacterial strains, which might be correlated to the diversity of genome encoded clock components. Based on statistical analyses of co-occurrences of the clock components homologous toSynechococcus elongatusPCC 7942, we propose putative networks of reduced and fully functional clock systems. Further, we studied KaiC sequence conservation to determine functionally important regions of diverged KaiC homologs. Biochemical characterization of exemplary cyanobacterial KaiC proteins as well as homologs from two thermophilic Archaea demonstrated that kinase activity is always present. However, a KaiA-mediated phosphorylation is only detectable in KaiC1 orthologs.ConclusionOur analysis of 11,264 genomes clearly demonstrates that components of theSynechococcus elongatusPCC 7942 circadian clock are present in Bacteria and Archaea. However, all components are less abundant in other organisms than Cyanobacteria and KaiA, Pex, LdpA, and CdpA are only present in the latter. Thus, only reduced KaiBC-based or even simpler, solely KaiC-based timing systems might exist outside of the cyanobacterial phylum, which might be capable of driving diurnal oscillations.
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Conversion between two conformational states of KaiC is induced by ATP hydrolysis as a trigger for cyanobacterial circadian oscillation. Sci Rep 2016; 6:32443. [PMID: 27580682 PMCID: PMC5007536 DOI: 10.1038/srep32443] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 08/03/2016] [Indexed: 11/12/2022] Open
Abstract
The cyanobacterial circadian oscillator can be reconstituted in vitro by mixing three clock proteins, KaiA, KaiB and KaiC, with ATP. KaiC is the only protein with circadian rhythmic activities. In the present study, we tracked the complex formation of the three Kai proteins over time using blue native (BN) polyacrylamide gel electrophoresis (PAGE), in which proteins are charged with the anionic dye Coomassie brilliant blue (CBB). KaiC was separated as three bands: the KaiABC complex, KaiC hexamer and KaiC monomer. However, no KaiC monomer was observed using gel filtration chromatography and CBB-free native PAGE. These data indicate two conformational states of KaiC hexamer and show that the ground-state KaiC (gs-KaiC) is stable and competent-state KaiC (cs-KaiC) is labile and degraded into monomers by the binding of CBB. Repeated conversions from gs-KaiC to cs-KaiC were observed over 24 h using an in vitro reconstitution system. Phosphorylation of KaiC promoted the conversion from gs-KaiC to cs-KaiC. KaiA sustained the gs-KaiC state, and KaiB bound only cs-KaiC. An E77Q/E78Q-KaiC variant that lacked N-terminal ATPase activity remained in the gs-KaiC state. Taken together, ATP hydrolysis induces the formation of cs-KaiC and promotes the binding of KaiB, which is a trigger for circadian oscillations.
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Murakami R, Mutoh R, Ishii K, Ishiura M. Circadian oscillations of KaiA-KaiC and KaiB-KaiC complex formations in an in vitro
reconstituted KaiABC clock oscillator. Genes Cells 2016; 21:890-900. [DOI: 10.1111/gtc.12392] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 05/31/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Reiko Murakami
- Center for Gene Research; Nagoya University; Furo-cho Chikusa-ku Nagoya 464-8602 Japan
| | - Risa Mutoh
- Center for Gene Research; Nagoya University; Furo-cho Chikusa-ku Nagoya 464-8602 Japan
| | - Ketaro Ishii
- Center for Gene Research; Nagoya University; Furo-cho Chikusa-ku Nagoya 464-8602 Japan
| | - Masahiro Ishiura
- Center for Gene Research; Nagoya University; Furo-cho Chikusa-ku Nagoya 464-8602 Japan
- Division of Biological Sciences; Nagoya University; Furo-cho Chikusa Nagoya 464-8602 Japan
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Iwasaki H, Kondo T. Circadian Timing Mechanism in the Prokaryotic Clock System of Cyanobacteria. J Biol Rhythms 2016; 19:436-44. [PMID: 15534323 DOI: 10.1177/0748730404269060] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cyanobacteria are the simplest organisms known to exhibit circadian rhythms and have provided experimental model systems for the dissection of basic properties of circadian organization at the molecular, physiological, and ecological levels. This review focuses on the molecular and genetic mechanisms of circadian rhythm generation in cyanobacteria. Recent analyses have revealed the existence of multiple feedback processes in the prokaryotic circadian system and have led to a novel molecular oscillator model. Here, the authors summarize current understanding of, and open questions about, the cyanobacterial oscillator.
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Affiliation(s)
- Hideo Iwasaki
- Division of Biological Science, Graduate School of Science, Nagoya University, Japan.
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30
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Ghosh A, Dutta D, Bandyopadhyay K, Parrack P. Characterization of the autophosphorylation property of HflX, a ribosome-binding GTPase from Escherichia coli. FEBS Open Bio 2016; 6:651-9. [PMID: 27398305 PMCID: PMC4932445 DOI: 10.1002/2211-5463.12065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Revised: 03/15/2016] [Accepted: 03/29/2016] [Indexed: 12/05/2022] Open
Abstract
Escherichia coli HflX belongs to the widely distributed but poorly characterized HflX family of translation factor‐related GTPases that is conserved from bacteria to humans. A 426‐residue polypeptide that binds 50S ribosomes and has both GTPase and ATPase activities, HflX also exhibits autophosphorylation activity. We show that HflX(C), a C‐terminal fragment of HflX, has an enhanced autophosphorylation activity compared to the full‐length protein. Using a chemical stability assay and thin layer chromatography, we have determined that phosphorylation occurs at a serine residue. Each of the nine serine residues of HflX(C) was mutated to alanine. It was found that all but S211A retained autophosphorylation activity, suggesting that S211, located in the P‐loop, was the likely site for autophosphorylation. While the S211A mutant lacked the autophosphorylation site, it possessed strong GTP binding and GTPase activities.
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Affiliation(s)
- Aditi Ghosh
- Department of Biochemistry Bose Institute Kolkata India
| | - Dipak Dutta
- Department of Biochemistry Bose Institute KolkataIndia; Present address: CSIR-Institute of Microbial Technology Sector 39A Chandigarh 160036 India
| | - Kaustav Bandyopadhyay
- Department of Biochemistry Bose Institute KolkataIndia; Present address: Department of Plant Biology The Samuel Roberts Noble Foundation Ardmore OK USA
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31
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Solovyov IA, Dobrovol’skaya EV, Moskalev AA. Genetic control of circadian rhythms and aging. RUSS J GENET+ 2016. [DOI: 10.1134/s1022795416040104] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Abstract
Life on earth is subject to daily and predictable fluctuations in light intensity, temperature, and humidity created by rotation of the earth. Circadian rhythms, generated by a circadian clock, control temporal programs of cellular physiology to facilitate adaptation to daily environmental changes. Circadian rhythms are nearly ubiquitous and are found in both prokaryotic and eukaryotic organisms. Here we introduce the molecular mechanism of the circadian clock in the model cyanobacterium Synechococcus elongatus PCC 7942. We review the current understanding of the cyanobacterial clock, emphasizing recent work that has generated a more comprehensive understanding of how the circadian oscillator becomes synchronized with the external environment and how information from the oscillator is transmitted to generate rhythms of biological activity. These results have changed how we think about the clock, shifting away from a linear model to one in which the clock is viewed as an interactive network of multifunctional components that are integrated into the context of the cell in order to pace and reset the oscillator. We conclude with a discussion of how this basic timekeeping mechanism differs in other cyanobacterial species and how information gleaned from work in cyanobacteria can be translated to understanding rhythmic phenomena in other prokaryotic systems.
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Proietto M, Bianchi MM, Ballario P, Brenna A. Epigenetic and Posttranslational Modifications in Light Signal Transduction and the Circadian Clock in Neurospora crassa. Int J Mol Sci 2015; 16:15347-83. [PMID: 26198228 PMCID: PMC4519903 DOI: 10.3390/ijms160715347] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 06/24/2015] [Accepted: 06/30/2015] [Indexed: 12/15/2022] Open
Abstract
Blue light, a key abiotic signal, regulates a wide variety of physiological processes in many organisms. One of these phenomena is the circadian rhythm presents in organisms sensitive to the phase-setting effects of blue light and under control of the daily alternation of light and dark. Circadian clocks consist of autoregulatory alternating negative and positive feedback loops intimately connected with the cellular metabolism and biochemical processes. Neurospora crassa provides an excellent model for studying the molecular mechanisms involved in these phenomena. The White Collar Complex (WCC), a blue-light receptor and transcription factor of the circadian oscillator, and Frequency (FRQ), the circadian clock pacemaker, are at the core of the Neurospora circadian system. The eukaryotic circadian clock relies on transcriptional/translational feedback loops: some proteins rhythmically repress their own synthesis by inhibiting the activity of their transcriptional factors, generating self-sustained oscillations over a period of about 24 h. One of the basic mechanisms that perpetuate self-sustained oscillations is post translation modification (PTM). The acronym PTM generically indicates the addition of acetyl, methyl, sumoyl, or phosphoric groups to various types of proteins. The protein can be regulatory or enzymatic or a component of the chromatin. PTMs influence protein stability, interaction, localization, activity, and chromatin packaging. Chromatin modification and PTMs have been implicated in regulating circadian clock function in Neurospora. Research into the epigenetic control of transcription factors such as WCC has yielded new insights into the temporal modulation of light-dependent gene transcription. Here we report on epigenetic and protein PTMs in the regulation of the Neurospora crassa circadian clock. We also present a model that illustrates the molecular mechanisms at the basis of the blue light control of the circadian clock.
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Affiliation(s)
- Marco Proietto
- Department of Biology and Biotechnologies "Charles Darwin", Sapienza-University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy.
| | - Michele Maria Bianchi
- Department of Biology and Biotechnologies "Charles Darwin", Sapienza-University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy.
| | - Paola Ballario
- Department of Biology and Biotechnologies "Charles Darwin", Sapienza-University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy.
- Pasteur Institute, Cenci Bolognetti Foundation and Department of Biology and Biotechnology "Charles Darwin", Sapienza-University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy.
| | - Andrea Brenna
- Department of Biology and Biotechnologies "Charles Darwin", Sapienza-University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy.
- Pasteur Institute, Cenci Bolognetti Foundation and Department of Biology and Biotechnology "Charles Darwin", Sapienza-University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy.
- Department of Biology, Division of Biochemistry, University of Fribourg, Chemin du Musée 5, Fribourg 1700, Switzerland.
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Lee DG, Kwon J, Eom CY, Kang YM, Roh SW, Lee KB, Choi JS. Directed analysis of cyanobacterial membrane phosphoproteome using stained phosphoproteins and titanium-enriched phosphopeptides. J Microbiol 2015; 53:279-87. [PMID: 25845541 DOI: 10.1007/s12275-015-5021-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 02/12/2015] [Accepted: 02/13/2015] [Indexed: 11/26/2022]
Abstract
Gel-free shotgun phosphoproteomics of unicellular cyanobacterium Synechocystis sp. PCC 6803 has not been reported up to now. The purpose of this study is to develop directed membrane phosphoproteomic method in Synechocystis sp. Total Synechocystis membrane proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and phosphoprotein-stained gel bands were selectively subjected to in-gel trypsin digestion. The phosphorylation sites of the resulting peptides were determined by assigning the neutral loss of [M-H(3)PO(4)] to Ser, Thr, and Tyr residues using nano-liquid chromatography 7 Tesla Fourier transform mass spectrometry. As an initial application, 111 proteins and 33 phosphoproteins were identified containing 11 integral membrane proteins. Identified four unknown phosphoproteins with transmembrane helices were suggested to be involved in membrane migration or transporters based on BLASTP search annotations. The overall distribution of hydrophobic amino acids in pTyr was lower in frequency than that of pSer or pThr. Positively charged amino acids were abundantly revealed in the surrounding amino acids centered on pTyr. A directed shotgun membrane phosphoproteomic strategy provided insight into understanding the fundamental regulatory processes underlying Ser, Thr, and Tyr phosphorylation in multi-layered membranous cyanobacteria.
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Affiliation(s)
- Dong-Gi Lee
- Biological Disaster Analysis Group, Korea Basic Science Institute, Daejeon, 305-806, Republic of Korea
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35
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Kitayama Y, Nishiwaki-Ohkawa T, Sugisawa Y, Kondo T. KaiC intersubunit communication facilitates robustness of circadian rhythms in cyanobacteria. Nat Commun 2014; 4:2897. [PMID: 24305644 PMCID: PMC3863973 DOI: 10.1038/ncomms3897] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 11/08/2013] [Indexed: 02/08/2023] Open
Abstract
The cyanobacterial circadian clock is the only model clock to have been reconstituted in vitro. KaiC, the central clock component, is a homohexameric ATPase with autokinase and autophosphatase activities. Changes in phosphorylation state have been proposed to switch KaiC’s activity between autokinase and autophosphatase. Here we analyse the molecular mechanism underlying the regulation of KaiC’s activity, in the context of its hexameric structure. We reconstitute KaiC hexamers containing different variant protomers, and measure their autophosphatase and autokinase activities. We identify two types of regulatory mechanisms with distinct functions. First, local interactions between adjacent phosphorylation sites regulate KaiC’s activities, coupling the ATPase and nucleotide-binding states at subunit interfaces of the CII domain. Second, the phosphorylation states of the protomers affect the overall activity of KaiC hexamers via intersubunit communication. Our findings indicate that intra-hexameric interactions play an important role in sustaining robust circadian rhythmicity. The cyanobacterial circadian oscillator comprises an autoregulatory loop that is driven by phosphorylation and dephosphorylation of the hexameric kinase KaiC. Kitayama et al. reveal how interactions between KaiC subunits regulate its catalytic activities and ensure robust circadian behaviour.
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Affiliation(s)
- Yohko Kitayama
- Division of Biological Science, Graduate School of Science, Nagoya University and CREST, Japan Science and Technology Agency (JST), Furo-cho, Chikusa-ku, Nagoya 464 8602, Japan
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Hatakeyama TS, Kaneko K. Homeostasis of the period of post-translational biochemical oscillators. FEBS Lett 2014; 588:2282-7. [PMID: 24859081 DOI: 10.1016/j.febslet.2014.05.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 05/01/2014] [Accepted: 05/09/2014] [Indexed: 11/15/2022]
Abstract
Generally, circadian clocks or biological oscillations are resistant to external conditions such as temperature and nutrient concentration. We propose that enzyme-limited competition provides a general mechanism of homeostasis of the period of post-translational oscillators based on protein modifications, and demonstrate it by nutrient compensation in a theoretical model of cyanobacterial circadian clock. The rate change by nutrient concentration is counterbalanced by the amount of available free enzyme, which occurs because of the competition among the various substrates for the limited enzyme. The temperature and nutrient compensation are determined by the postulate that the catalytic modification reactions are rate limiting.
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Affiliation(s)
- Tetsuhiro S Hatakeyama
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
| | - Kunihiko Kaneko
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
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Exchange of ADP with ATP in the CII ATPase domain promotes autophosphorylation of cyanobacterial clock protein KaiC. Proc Natl Acad Sci U S A 2014; 111:4455-60. [PMID: 24616498 DOI: 10.1073/pnas.1319353111] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The cyanobacterial circadian oscillator can be reconstituted in vitro. In the presence of KaiA and KaiB, the phosphorylation state of KaiC oscillates with a periodicity of ∼24 h. KaiC is a hexameric P-loop ATPase with autophosphorylation and autodephosphorylation activities. Recently, we found that dephosphorylation of KaiC occurs via reversal of the phosphorylation reaction: a phosphate group attached to Ser431/Thr432 is transferred to KaiC-bound ADP to generate ATP, which is subsequently hydrolyzed. This unusual reaction mechanism suggests that the KaiC phosphorylation rhythm is sustained by periodic shifts in the equilibrium of the reversible autophosphorylation reaction, the molecular basis of which has never been elucidated. Because KaiC-bound ATP and ADP serve as substrates for the forward and reverse reactions, respectively, we investigated the regulation of the nucleotide-bound state of KaiC. In the absence of KaiA, the condition in which the reverse reaction proceeds, KaiC favored the ADP-bound state. KaiA increased the ratio of ATP to total KaiC-bound nucleotides by facilitating the release of bound ADP and the incorporation of exogenous ATP, allowing the forward reaction to proceed. When both KaiA and KaiB were present, the ratio of ATP to total bound nucleotides exhibited a circadian rhythm, whose phase was advanced by several hours relative to that of the phosphorylation rhythm. Based on these findings, we propose that the direction of the reversible autophosphorylation reaction is regulated by KaiA and KaiB at the level of substrate availability and that this regulation sustains the oscillation of the phosphorylation state of KaiC.
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Ishii K, Terauchi S, Murakami R, Valencia Swain J, Mutoh R, Mino H, Maki K, Arata T, Ishiura M. Site-directed spin labeling-electron spin resonance mapping of the residues of cyanobacterial clock protein KaiA that are affected by KaiA-KaiC interaction. Genes Cells 2014; 19:297-324. [PMID: 24495257 DOI: 10.1111/gtc.12130] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 12/12/2013] [Indexed: 11/28/2022]
Abstract
The cyanobacterial clock proteins KaiA, KaiB and KaiC interact with each other to generate circadian oscillations. We have identified the residues of the KaiA homodimer affected through association with hexameric KaiC (KaiC6mer) using a spin-label-tagged KaiA C-terminal domain protein (KaiAc) and performing electron spin resonance (ESR) analysis. Cys substitution and/or the attachment of a spin label to residues located at the bottom area of the KaiAc concave surface, a KaiC-binding groove, hindered the association of KaiAc with KaiC6mer, suggesting that the groove likely mediates the interaction with KaiC6mer. The residues affected by KaiC6mer association were concentrated in the three areas: the concave surface, a lobe-like structure (a mobile lobe near the concave surface) and a region adjacent to both the concave surface and the mobile lobe. The distance between the two E254, D255, L258 and R252 residues located on the mobile lobe decreased after KaiC association, suggesting that the two mobile lobes approach each other during the interaction. Analyzing the molecular dynamics of KaiAc showed that these structural changes suggested by ESR analysis were possible. Furthermore, the analyses identified three asymmetries in KaiAc dynamic structures, which gave us a possible explanation of an asymmetric association of KaiAc with KaiC6mer.
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Affiliation(s)
- Kentaro Ishii
- Center for Gene Research, Nagoya University, Furo, Chikusa, Nagoya, Aichi, 464-8602, Japan; Division of Biological Science, Graduate School of Science, Osaka University, Machikaneyama, Toyonaka, Osaka, 560-0043, Japan
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Ma L, Ranganathan R. Systems-level characterization of the kernel mechanism of the cyanobacterial circadian oscillator. Biosystems 2014; 117:30-9. [PMID: 24444761 DOI: 10.1016/j.biosystems.2014.01.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Revised: 12/19/2013] [Accepted: 01/07/2014] [Indexed: 10/25/2022]
Abstract
Circadian clock is an essential molecular regulatory mechanism that coordinates daily biological processes. Toward understanding the design principles of the circadian mechanism in cyanobacteria, the only prokaryotes reported to possess circadian rhythmicity, mathematical models have been used as important tools to help elucidate the complicated biochemical processes. In this study, we focus on elucidating the underlying systems properties that drive the oscillation of the cyanobacterial clockwork. We apply combined methods of time scale separation, phase space analysis, bifurcation analysis and sensitivity analysis to a model of the in vitro cyanobacterial circadian clock proposed by us recently. The original model is reduced to a three-dimensional slow subsystem by time scale separation. Phase space analysis of the reduced subsystem shows that the null-surface of the Serine-phosphorylated state (S-state) of KaiC is a bistable surface, and that the characteristic of the phase portrait indicates that the kernel mechanism of the clockwork behaves as a relaxation oscillator induced by interlinked positive and negative feedback loops. Phase space analysis together with perturbation analysis supports our previous viewpoint that the S-state of KaiC is plausibly a key component for the protein regulatory network of the cyanobacterial circadian clock.
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Affiliation(s)
- Lan Ma
- Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, United States; Green Center for Systems Biology, Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States.
| | - Rama Ranganathan
- Green Center for Systems Biology, Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, United States
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Diversity of KaiC-based timing systems in marine Cyanobacteria. Mar Genomics 2014; 14:3-16. [PMID: 24388874 DOI: 10.1016/j.margen.2013.12.006] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 11/19/2013] [Accepted: 12/18/2013] [Indexed: 12/21/2022]
Abstract
The coordination of biological activities into daily cycles provides an important advantage for the fitness of diverse organisms. Most eukaryotes possess an internal clock ticking with a periodicity of about one day to anticipate sunrise and sunset. The 24-hour period of the free-running rhythm is highly robust against many changes in the natural environment. Among prokaryotes, only Cyanobacteria are known to harbor such a circadian clock. Its core oscillator consists of just three proteins, KaiA, KaiB, and KaiC that produce 24-hour oscillations of KaiC phosphorylation, even in vitro. This unique three-protein oscillator is well documented for the freshwater cyanobacterium Synechococcus elongatus PCC 7942. Several physiological studies demonstrate a circadian clock also for other Cyanobacteria including marine species. Genes for the core clock components are present in nearly all marine cyanobacterial species, though there are large differences in the specific composition of these genes. In the first section of this review we summarize data on the model circadian clock from S. elongatus PCC 7942 and compare it to the reduced clock system of the marine cyanobacterium Prochlorococcus marinus MED4. In the second part we discuss the diversity of timing mechanisms in other marine Cyanobacteria with regard to the presence or absence of different components of the clock.
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Mutoh R, Nishimura A, Yasui S, Onai K, Ishiura M. The ATP-mediated regulation of KaiB-KaiC interaction in the cyanobacterial circadian clock. PLoS One 2013; 8:e80200. [PMID: 24244649 PMCID: PMC3823767 DOI: 10.1371/journal.pone.0080200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 10/01/2013] [Indexed: 11/19/2022] Open
Abstract
The cyanobacterial circadian clock oscillator is composed of three clock proteins—KaiA, KaiB, and KaiC, and interactions among the three Kai proteins generate clock oscillation in vitro. However, the regulation of these interactions remains to be solved. Here, we demonstrated that ATP regulates formation of the KaiB-KaiC complex. In the absence of ATP, KaiC was monomeric (KaiC1mer) and formed a complex with KaiB. The addition of ATP plus Mg2+ (Mg-ATP), but not that of ATP only, to the KaiB-KaiC1mer complex induced the hexamerization of KaiC and the concomitant release of KaiB from the KaiB-KaiC1mer complex, indicating that Mg-ATP and KaiB compete each other for KaiC. In the presence of ATP and Mg2+ (Mg-ATP), KaiC became a homohexameric ATPase (KaiC6mer) with bound Mg-ATP and formed a complex with KaiB, but KaiC hexamerized by unhydrolyzable substrates such as ATP and Mg-ATP analogs, did not. A KaiC N-terminal domain protein, but not its C-terminal one, formed a complex with KaiB, indicating that KaiC associates with KaiB via its N-terminal domain. A mutant KaiC6mer lacking N-terminal ATPase activity did not form a complex with KaiB whereas a mutant lacking C-terminal ATPase activity did. Thus, the N-terminal domain of KaiC is responsible for formation of the KaiB-KaiC complex, and the hydrolysis of the ATP bound to N-terminal ATPase motifs on KaiC6mer is required for formation of the KaiB-KaiC6mer complex. KaiC6mer that had been hexamerized with ADP plus aluminum fluoride, which are considered to mimic ADP-Pi state, formed a complex with KaiB, suggesting that KaiB is able to associate with KaiC6mer with bound ADP-Pi.
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Affiliation(s)
- Risa Mutoh
- Center for Gene Research, Nagoya University, Nagoya, Aichi, Japan
| | - Atsuhito Nishimura
- Center for Gene Research, Nagoya University, Nagoya, Aichi, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan
| | - So Yasui
- Center for Gene Research, Nagoya University, Nagoya, Aichi, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan
| | - Kiyoshi Onai
- Center for Gene Research, Nagoya University, Nagoya, Aichi, Japan
| | - Masahiro Ishiura
- Center for Gene Research, Nagoya University, Nagoya, Aichi, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Aichi, Japan
- * E-mail:
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Liang PJ, Han WY, Huang QH, Li YZ, Ni JF, She QX, Shen YL. Knockouts of RecA-Like Proteins RadC1 and RadC2 Have Distinct Responses to DNA Damage Agents in Sulfolobus islandicus. J Genet Genomics 2013; 40:533-42. [DOI: 10.1016/j.jgg.2013.05.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2013] [Revised: 05/17/2013] [Accepted: 05/22/2013] [Indexed: 11/30/2022]
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Loza-Correa M, Sahr T, Rolando M, Daniels C, Petit P, Skarina T, Gomez Valero L, Dervins-Ravault D, Honoré N, Savchenko A, Buchrieser C. The Legionella pneumophila kai operon is implicated in stress response and confers fitness in competitive environments. Environ Microbiol 2013; 16:359-81. [PMID: 23957615 DOI: 10.1111/1462-2920.12223] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Revised: 07/16/2013] [Accepted: 07/19/2013] [Indexed: 01/22/2023]
Abstract
Legionella pneumophila uses aquatic protozoa as replication niche and protection from harsh environments. Although L. pneumophila is not known to have a circadian clock, it encodes homologues of the KaiBC proteins of Cyanobacteria that regulate circadian gene expression. We show that L. pneumophila kaiB, kaiC and the downstream gene lpp1114, are transcribed as a unit under the control of the stress sigma factor RpoS. KaiC and KaiB of L. pneumophila do not interact as evidenced by yeast and bacterial two-hybrid analyses. Fusion of the C-terminal residues of cyanobacterial KaiB to Legionella KaiB restores their interaction. In contrast, KaiC of L. pneumophila conserved autophosphorylation activity, but KaiB does not trigger the dephosphorylation of KaiC like in Cyanobacteria. The crystal structure of L. pneumophila KaiB suggests that it is an oxidoreductase-like protein with a typical thioredoxin fold. Indeed, mutant analyses revealed that the kai operon-encoded proteins increase fitness of L. pneumophila in competitive environments, and confer higher resistance to oxidative and sodium stress. The phylogenetic analysis indicates that L. pneumophila KaiBC resemble Synechosystis KaiC2B2 and not circadian KaiB1C1. Thus, the L. pneumophila Kai proteins do not encode a circadian clock, but enhance stress resistance and adaption to changes in the environments.
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Affiliation(s)
- Maria Loza-Correa
- Institut Pasteur, Biologie des Bactéries Intracellulaires, Paris, France; CNRS UMR 3525, Paris, France
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Elucidation of the role of clp protease components in circadian rhythm by genetic deletion and overexpression in cyanobacteria. J Bacteriol 2013; 195:4517-26. [PMID: 23913328 DOI: 10.1128/jb.00300-13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the cyanobacterium Synechococcus elongatus PCC7942, KaiA, KaiB, and KaiC are essential elements of the circadian clock, and Kai-based oscillation is thought to be the basic circadian timing mechanism. The Kai-based oscillator coupled with transcription/translation feedback and other intercellular factors maintains the stability of the 24-hour period in vivo. In this study, we showed that disruption of the Clp protease family genes clpP1, clpP2, and clpX and the overexpression of clpP3 cause long-period phenotypes. There were no significant changes in the levels of the clock proteins in these mutants. The overexpression of clpX led to a decrease in kaiBC promoter activity, the disruption of the circadian rhythm, and eventually cell death. However, after the transient overexpression of clpX, the kaiBC gene expression rhythm recovered after a few days. The rhythm phase after recovery was almost the same as the phase before clpX overexpression. These results suggest that the core Kai-based oscillation was not affected by clpX overexpression. Moreover, we showed that the overexpression of clpX sequentially upregulated ribosomal protein subunit mRNA levels, followed by upregulation of other genes, including the clock genes. Additionally, we found that the disruption of clpX decreased the expression of the ribosomal protein subunits. Finally, we showed that the circadian period was prolonged following the addition of a translation inhibitor at a low concentration. These results suggest that translational efficiency affects the circadian period and that clpX participates in the control of translation efficiency by regulating the transcription of ribosomal protein genes.
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Egli M, Johnson CH. A circadian clock nanomachine that runs without transcription or translation. Curr Opin Neurobiol 2013; 23:732-40. [PMID: 23571120 DOI: 10.1016/j.conb.2013.02.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 02/21/2013] [Accepted: 02/23/2013] [Indexed: 11/15/2022]
Abstract
The biochemical basis of circadian timekeeping is best characterized in cyanobacteria. The structures of its key molecular players, KaiA, KaiB, and KaiC are known and these proteins can reconstitute a remarkable circadian oscillation in a test tube. KaiC is rhythmically phosphorylated and its phospho-status is a marker of circadian phase that regulates ATPase activity and the oscillating assembly of a nanomachine. Analyses of the nanomachines have revealed how their timing circuit is ratcheted to be unidirectional and how they stay in synch to ensure a robust oscillator. These insights are likely to elucidate circadian timekeeping in higher organisms, including how transcription and translation could appear to be a core circadian timer when the true pacemaker is an embedded biochemical oscillator.
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Affiliation(s)
- Martin Egli
- Department of Biochemistry, Vanderbilt University, School of Medicine, Nashville, TN 37232, USA.
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Egli M, Pattanayek R, Sheehan JH, Xu Y, Mori T, Smith JA, Johnson CH. Loop-loop interactions regulate KaiA-stimulated KaiC phosphorylation in the cyanobacterial KaiABC circadian clock. Biochemistry 2013; 52:1208-20. [PMID: 23351065 PMCID: PMC3587310 DOI: 10.1021/bi301691a] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Synechococcus elongatus KaiA, KaiB, and KaiC proteins in the presence of ATP generate a post-translational oscillator that runs in a temperature-compensated manner with a period of 24 h. KaiA dimer stimulates phosphorylation of KaiC hexamer at two sites per subunit, T432 and S431, and KaiB dimers antagonize KaiA action and induce KaiC subunit exchange. Neither the mechanism of KaiA-stimulated KaiC phosphorylation nor that of KaiB-mediated KaiC dephosphorylation is understood in detail at present. We demonstrate here that the A422V KaiC mutant sheds light on the former mechanism. It was previously reported that A422V is less sensitive to dark pulse-induced phase resetting and has a reduced amplitude of the KaiC phosphorylation rhythm in vivo. A422 maps to a loop (422-loop) that continues toward the phosphorylation sites. By pulling on the C-terminal peptide of KaiC (A-loop), KaiA removes restraints from the adjacent 422-loop whose increased flexibility indirectly promotes kinase activity. We found in the crystal structure that A422V KaiC lacks phosphorylation at S431 and exhibits a subtle, local conformational change relative to wild-type KaiC. Molecular dynamics simulations indicate higher mobility of the 422-loop in the absence of the A-loop and mobility differences in other areas associated with phosphorylation activity between wild-type and mutant KaiCs. The A-loop-422-loop relay that informs KaiC phosphorylation sites of KaiA dimer binding propagates to loops from neighboring KaiC subunits, thus providing support for a concerted allosteric mechanism of phosphorylation.
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Affiliation(s)
- Martin Egli
- Department of Biochemistry, Vanderbilt University, School of Medicine, Nashville, TN 37232, USA.
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Abstract
Mammals synchronize their circadian activity primarily to the cycles of light and darkness in the environment. This is achieved by ocular photoreception relaying signals to the suprachiasmatic nucleus (SCN) in the hypothalamus. Signals from the SCN cause the synchronization of independent circadian clocks throughout the body to appropriate phases. Signals that can entrain these peripheral clocks include humoral signals, metabolic factors, and body temperature. At the level of individual tissues, thousands of genes are brought to unique phases through the actions of a local transcription/translation-based feedback oscillator and systemic cues. In this molecular clock, the proteins CLOCK and BMAL1 cause the transcription of genes which ultimately feedback and inhibit CLOCK and BMAL1 transcriptional activity. Finally, there are also other molecular circadian oscillators which can act independently of the transcription-based clock in all species which have been tested.
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Affiliation(s)
- Ethan D Buhr
- Department of Ophthalmology, University of Washington, 1959 NE Pacific St, 356485 BB-857 HSB, Seattle, WA 98195, USA
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Pattanayek R, Sidiqi SK, Egli M. Crystal structure of the redox-active cofactor dibromothymoquinone bound to circadian clock protein KaiA and structural basis for dibromothymoquinone's ability to prevent stimulation of KaiC phosphorylation by KaiA. Biochemistry 2012; 51:8050-2. [PMID: 23020633 DOI: 10.1021/bi301222t] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
KaiA protein that stimulates KaiC phosphorylation in the cyanobacterial circadian clock was recently shown to be destabilized by dibromothymoquinone (DBMIB), thus revealing KaiA as a sensor of the plastoquinone (PQ) redox state and suggesting an indirect control of the clock by light through PQ redox changes. Here we show using X-ray crystallography that several DBMIBs are bound to KaiA dimer. Some binding modes are consistent with oligomerization of N-terminal KaiA pseudoreceiver domains and/or reduced interdomain flexibility. DBMIB bound to the C-terminal KaiA (C-KaiA) domain and limited stimulation of KaiC kinase activity by C-KaiA in the presence of DBMIB demonstrate that the cofactor may weakly inhibit KaiA-KaiC binding.
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Affiliation(s)
- Rekha Pattanayek
- Department of Biochemistry, Vanderbilt University, School of Medicine, Nashville, TN 37232, USA
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van Ooijen G, Millar AJ. Non-transcriptional oscillators in circadian timekeeping. Trends Biochem Sci 2012; 37:484-92. [PMID: 22917814 DOI: 10.1016/j.tibs.2012.07.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Revised: 07/20/2012] [Accepted: 07/26/2012] [Indexed: 01/10/2023]
Abstract
Circadian clocks have evolved as an adaptation to life on a rotating planet, and orchestrate rhythmic changes in physiology to match the time of day. For decades, cellular circadian rhythms were considered to solely result from feedback between the products of rhythmically expressed genes. These transcriptional/translational feedback loops (TTFLs) have been ubiquitously studied, and explain the majority of circadian outputs. In recent years, however, non-transcriptional processes were shown to be major contributors to circadian rhythmicity. These key findings have profound implications on our understanding of the evolution and mechanistic basis of cellular circadian timekeeping. This review summarises and discusses these results and the experimental and theoretical evidence of a possible relation between non-transcriptional oscillator (NTO) mechanisms and TTFL oscillations.
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Affiliation(s)
- Gerben van Ooijen
- SynthSys, University of Edinburgh, The Kings Buildings, Mayfield Road, EH9 3JD, Edinburgh, UK
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Ma L, Ranganathan R. Quantifying the rhythm of KaiB-C interaction for in vitro cyanobacterial circadian clock. PLoS One 2012; 7:e42581. [PMID: 22900029 PMCID: PMC3416856 DOI: 10.1371/journal.pone.0042581] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 07/10/2012] [Indexed: 11/18/2022] Open
Abstract
An oscillator consisting of KaiA, KaiB, and KaiC proteins comprises the core of cyanobacterial circadian clock. While one key reaction in this process--KaiC phosphorylation--has been extensively investigated and modeled, other key processes, such as the interactions among Kai proteins, are not understood well. Specifically, different experimental techniques have yielded inconsistent views about Kai A, B, and C interactions. Here, we first propose a mathematical model of cyanobacterial circadian clock that explains the recently observed dynamics of the four phospho-states of KaiC as well as the interactions among the three Kai proteins. Simulations of the model show that the interaction between KaiB and KaiC oscillates with the same period as the phosphorylation of KaiC, but displays a phase delay of ∼8 hr relative to the total phosphorylated KaiC. Secondly, this prediction on KaiB-C interaction are evaluated using a novel FRET (Fluorescence Resonance Energy Transfer)-based assay by tagging fluorescent proteins Cerulean and Venus to KaiC and KaiB, respectively, and reconstituting fluorescent protein-labeled in vitro clock. The data show that the KaiB∶KaiC interaction indeed oscillates with ∼24 hr periodicity and ∼8 hr phase delay relative to KaiC phosphorylation, consistent with model prediction. Moreover, it is noteworthy that our model indicates that the interlinked positive and negative feedback loops are the underlying mechanism for oscillation, with the serine phosphorylated-state (the "S-state") of KaiC being a hub for the feedback loops. Because the kinetics of the KaiB-C interaction faithfully follows that of the S-state, the FRET measurement may provide an important real-time probe in quantitative study of the cyanobacterial circadian clock.
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Affiliation(s)
- Lan Ma
- Bioengineering Department, University of Texas at Dallas, Richardson, Texas, United States of America.
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