1
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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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2
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Pitsawong W, Pádua RAP, Grant T, Hoemberger M, Otten R, Bradshaw N, Grigorieff N, Kern D. From primordial clocks to circadian oscillators. Nature 2023; 616:183-189. [PMID: 36949197 PMCID: PMC10076222 DOI: 10.1038/s41586-023-05836-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 02/13/2023] [Indexed: 03/24/2023]
Abstract
Circadian rhythms play an essential part in many biological processes, and only three prokaryotic proteins are required to constitute a true post-translational circadian oscillator1. The evolutionary history of the three Kai proteins indicates that KaiC is the oldest member and a central component of the clock2. Subsequent additions of KaiB and KaiA regulate the phosphorylation state of KaiC for time synchronization. The canonical KaiABC system in cyanobacteria is well understood3-6, but little is known about more ancient systems that only possess KaiBC. However, there are reports that they might exhibit a basic, hourglass-like timekeeping mechanism7-9. Here we investigate the primordial circadian clock in Rhodobacter sphaeroides, which contains only KaiBC, to elucidate its inner workings despite missing KaiA. Using a combination of X-ray crystallography and cryogenic electron microscopy, we find a new dodecameric fold for KaiC, in which two hexamers are held together by a coiled-coil bundle of 12 helices. This interaction is formed by the carboxy-terminal extension of KaiC and serves as an ancient regulatory moiety that is later superseded by KaiA. A coiled-coil register shift between daytime and night-time conformations is connected to phosphorylation sites through a long-range allosteric network that spans over 140 Å. Our kinetic data identify the difference in the ATP-to-ADP ratio between day and night as the environmental cue that drives the clock. They also unravel mechanistic details that shed light on the evolution of self-sustained oscillators.
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Affiliation(s)
- Warintra Pitsawong
- Howard Hughes Medical Institute and Department of Biochemistry, Brandeis University, Waltham, MA, USA
- Biomolecular Discovery, Relay Therapeutics, Cambridge, MA, USA
| | - Ricardo A P Pádua
- Howard Hughes Medical Institute and Department of Biochemistry, Brandeis University, Waltham, MA, USA
| | - Timothy Grant
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
- John and Jeanne Rowe Center for Research in Virology, Morgridge Institute for Research, Madison, Madison, WI, USA
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, USA
| | - Marc Hoemberger
- Howard Hughes Medical Institute and Department of Biochemistry, Brandeis University, Waltham, MA, USA
- Treeline Biosciences, Watertown, MA, USA
| | - Renee Otten
- Howard Hughes Medical Institute and Department of Biochemistry, Brandeis University, Waltham, MA, USA
- Treeline Biosciences, Watertown, MA, USA
| | - Niels Bradshaw
- Department of Biochemistry, Brandeis University, Waltham, MA, USA
| | - Nikolaus Grigorieff
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
- Howard Hughes Medical Institute, RNA Therapeutics Institute, University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Dorothee Kern
- Howard Hughes Medical Institute and Department of Biochemistry, Brandeis University, Waltham, MA, USA.
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3
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Swan JA, Sandate CR, Chavan AG, Freeberg AM, Etwaru D, Ernst DC, Palacios JG, Golden SS, LiWang A, Lander GC, Partch CL. Coupling of distant ATPase domains in the circadian clock protein KaiC. Nat Struct Mol Biol 2022; 29:759-766. [PMID: 35864165 DOI: 10.1038/s41594-022-00803-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 06/06/2022] [Indexed: 11/09/2022]
Abstract
The AAA+ family member KaiC is the central pacemaker for circadian rhythms in the cyanobacterium Synechococcus elongatus. Composed of two hexameric rings of adenosine triphosphatase (ATPase) domains with tightly coupled activities, KaiC undergoes a cycle of autophosphorylation and autodephosphorylation on its C-terminal (CII) domain that restricts binding of clock proteins on its N-terminal (CI) domain to the evening. Here, we use cryogenic-electron microscopy to investigate how daytime and nighttime states of CII regulate KaiB binding on CI. We find that the CII hexamer is destabilized during the day but takes on a rigidified C2-symmetric state at night, concomitant with ring-ring compression. Residues at the CI-CII interface are required for phospho-dependent KaiB association, coupling ATPase activity on CI to cooperative KaiB recruitment. Together, these studies clarify a key step in the regulation of cyanobacterial circadian rhythms by KaiC phosphorylation.
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Affiliation(s)
- Jeffrey A Swan
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA, USA
| | - Colby R Sandate
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA
| | - Archana G Chavan
- Department of Chemistry and Biochemistry, University of California, Merced, CA, USA
| | - Alfred M Freeberg
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA, USA
| | - Diana Etwaru
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA, USA
| | - Dustin C Ernst
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, USA
| | - Joseph G Palacios
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA, USA
| | - Susan S Golden
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA, USA.,Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Andy LiWang
- Department of Chemistry and Biochemistry, University of California, Merced, CA, USA.,Center for Circadian Biology, University of California, San Diego, La Jolla, CA, USA.,Center for Cellular and Biomolecular Machines, University of California, Merced, CA, USA
| | - Gabriel C Lander
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, USA.
| | - Carrie L Partch
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA, USA. .,Division of Biological Sciences, University of California, San Diego, La Jolla, CA, USA.
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4
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Yunoki Y, Matsumoto A, Morishima K, Martel A, Porcar L, Sato N, Yogo R, Tominaga T, Inoue R, Yagi-Utsumi M, Okuda A, Shimizu M, Urade R, Terauchi K, Kono H, Yagi H, Kato K, Sugiyama M. Overall structure of fully assembled cyanobacterial KaiABC circadian clock complex by an integrated experimental-computational approach. Commun Biol 2022; 5:184. [PMID: 35273347 PMCID: PMC8913699 DOI: 10.1038/s42003-022-03143-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 02/08/2022] [Indexed: 12/24/2022] Open
Abstract
In the cyanobacterial circadian clock system, KaiA, KaiB and KaiC periodically assemble into a large complex. Here we determined the overall structure of their fully assembled complex by integrating experimental and computational approaches. Small-angle X-ray and inverse contrast matching small-angle neutron scatterings coupled with size-exclusion chromatography provided constraints to highlight the spatial arrangements of the N-terminal domains of KaiA, which were not resolved in the previous structural analyses. Computationally built 20 million structural models of the complex were screened out utilizing the constrains and then subjected to molecular dynamics simulations to examine their stabilities. The final model suggests that, despite large fluctuation of the KaiA N-terminal domains, their preferential positionings mask the hydrophobic surface of the KaiA C-terminal domains, hindering additional KaiA-KaiC interactions. Thus, our integrative approach provides a useful tool to resolve large complex structures harboring dynamically fluctuating domains. The revealed full KaiA12B6C6 complex is assembled including the dynamic and asynchronous KaiA N-terminal domains that have been missing in cryo-EM structures.
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Affiliation(s)
- Yasuhiro Yunoki
- Exploratory Research Center on Life and Living Systems (ExCELLS) and Institute for Molecular Science (IMS), National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, 444-8787, Japan.,Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuhoku, Nagoya, 467-8603, Japan.,Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashironishi, Kumatori, Sennan-gun, Osaka, 590-0494, Japan
| | - Atsushi Matsumoto
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology (QST), Umemidai, Kizu, Kyoto, 619-0215, Japan
| | - Ken Morishima
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashironishi, Kumatori, Sennan-gun, Osaka, 590-0494, Japan
| | - Anne Martel
- Institut Laue-Langevin, 71, avenue des martyrs, 38042, Grenoble, France
| | - Lionel Porcar
- Institut Laue-Langevin, 71, avenue des martyrs, 38042, Grenoble, France
| | - Nobuhiro Sato
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashironishi, Kumatori, Sennan-gun, Osaka, 590-0494, Japan
| | - Rina Yogo
- Exploratory Research Center on Life and Living Systems (ExCELLS) and Institute for Molecular Science (IMS), National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, 444-8787, Japan.,Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuhoku, Nagoya, 467-8603, Japan.,Biomedical Research Centre, School of Biomedical Engineering, The University of British Columbia, 2222 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
| | - Taiki Tominaga
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Ibaraki, 319-1106, Japan
| | - Rintaro Inoue
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashironishi, Kumatori, Sennan-gun, Osaka, 590-0494, Japan
| | - Maho Yagi-Utsumi
- Exploratory Research Center on Life and Living Systems (ExCELLS) and Institute for Molecular Science (IMS), National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, 444-8787, Japan.,Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuhoku, Nagoya, 467-8603, Japan
| | - Aya Okuda
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashironishi, Kumatori, Sennan-gun, Osaka, 590-0494, Japan
| | - Masahiro Shimizu
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashironishi, Kumatori, Sennan-gun, Osaka, 590-0494, Japan
| | - Reiko Urade
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashironishi, Kumatori, Sennan-gun, Osaka, 590-0494, Japan
| | - Kazuki Terauchi
- Graduate School of Life Sciences, Ritsumeikan University, 1-1-1 Noji-higashi, Kusatsu, Shiga, 525-8577, Japan
| | - Hidetoshi Kono
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology (QST), Umemidai, Kizu, Kyoto, 619-0215, Japan.
| | - Hirokazu Yagi
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuhoku, Nagoya, 467-8603, Japan.
| | - Koichi Kato
- Exploratory Research Center on Life and Living Systems (ExCELLS) and Institute for Molecular Science (IMS), National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, 444-8787, Japan. .,Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuhoku, Nagoya, 467-8603, Japan.
| | - Masaaki Sugiyama
- Institute for Integrated Radiation and Nuclear Science, Kyoto University, 2-1010 Asashironishi, Kumatori, Sennan-gun, Osaka, 590-0494, Japan.
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5
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Koda SI, Saito S. Multimeric structure enables the acceleration of KaiB-KaiC complex formation induced by ADP/ATP exchange inhibition. PLoS Comput Biol 2022; 18:e1009243. [PMID: 35255087 PMCID: PMC8929707 DOI: 10.1371/journal.pcbi.1009243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 03/17/2022] [Accepted: 02/25/2022] [Indexed: 11/19/2022] Open
Abstract
Circadian clocks tick a rhythm with a nearly 24-hour period in a variety of organisms. In the clock proteins of cyanobacteria, KaiA, KaiB, and KaiC, known as a minimum circadian clock, the slow KaiB-KaiC complex formation is essential in determining the clock period. This complex formation, occurring when the C1 domain of KaiC hexamer binds ADP molecules produced by the ATPase activity of C1, is considered to be promoted by accumulating ADP molecules in C1 through inhibiting the ADP/ATP exchange (ADP release) rather than activating the ATP hydrolysis (ADP production). Significantly, this ADP/ATP exchange inhibition accelerates the complex formation together with its promotion, implying a potential role in the period robustness under environmental perturbations. However, the molecular mechanism of this simultaneous promotion and acceleration remains elusive because inhibition of a backward process generally slows down the whole process. In this article, to investigate the mechanism, we build several reaction models of the complex formation with the pre-binding process concerning the ATPase activity. In these models, six KaiB monomers cooperatively and rapidly bind to C1 when C1 binds ADP molecules more than a given threshold while stabilizing the binding-competent conformation of C1. Through comparison among the models proposed here, we then extract three requirements for the simultaneous promotion and acceleration: the stabilization of the binding-competent C1 by KaiB binding, slow ADP/ATP exchange in the binding-competent C1, and relatively fast ADP/ATP exchange occurring in the binding-incompetent C1 in the presence of KaiB. The last two requirements oblige KaiC to form a multimer. Moreover, as a natural consequence, the present models can also explain why the binding of KaiB to C1 reduces the ATPase activity of C1. Circadian clocks tick a rhythm with a nearly 24-hour period in various organisms. The cyanobacterial circadian clock, composed of only three proteins, KaiA, KaiB, and KaiC, has attracted much attention because of its simplicity. The slow KaiB-KaiC complex formation is essential in determining the clock period in this system. Significantly, this complex formation is accelerated together with its promotion, implying a potential role in the period-keeping mechanism. However, this simultaneous promotion and acceleration is theoretically exceptional because this complex formation is promoted by inhibiting a backward process, which generally slows down the whole process. In this article, we investigate the molecular mechanism of this phenomenon by building mathematical models to find that the binding of KaiB to C1 must lower the ADP/ATP exchange of the C1 domain of KaiC via stabilizing the binding-competent conformation of C1. The present results would be of benefit for future investigations on functional roles of the simultaneous promotion and acceleration in the KaiABC oscillator.
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Affiliation(s)
- Shin-ichi Koda
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki, Aichi, Japan
- School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
- * E-mail: (SK); (SS)
| | - Shinji Saito
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki, Aichi, Japan
- School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
- * E-mail: (SK); (SS)
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6
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Chow GK, Chavan AG, Heisler J, Chang YG, Zhang N, LiWang A, Britt RD. A Night-Time Edge Site Intermediate in the Cyanobacterial Circadian Clock Identified by EPR Spectroscopy. J Am Chem Soc 2022; 144:184-194. [PMID: 34979080 DOI: 10.1021/jacs.1c08103] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
As the only circadian oscillator that can be reconstituted in vitro with its constituent proteins KaiA, KaiB, and KaiC using ATP as an energy source, the cyanobacterial circadian oscillator serves as a model system for detailed mechanistic studies of day-night transitions of circadian clocks in general. The day-to-night transition occurs when KaiB forms a night-time complex with KaiC to sequester KaiA, the latter of which interacts with KaiC during the day to promote KaiC autophosphorylation. However, how KaiB forms the complex with KaiC remains poorly understood, despite the available structures of KaiB bound to hexameric KaiC. It has been postulated that KaiB-KaiC binding is regulated by inter-KaiB cooperativity. Here, using spin labeling continuous-wave electron paramagnetic resonance spectroscopy, we identified and quantified two subpopulations of KaiC-bound KaiB, corresponding to the "bulk" and "edge" KaiBC sites in stoichiometric and substoichiometric KaiBiC6 complexes (i = 1-5). We provide kinetic evidence to support the intermediacy of the "edge" KaiBC sites as bridges and nucleation sites between free KaiB and the "bulk" KaiBC sites. Furthermore, we show that the relative abundance of "edge" and "bulk" sites is dependent on both KaiC phosphostate and KaiA, supporting the notion of phosphorylation-state controlled inter-KaiB cooperativity. Finally, we demonstrate that the interconversion between the two subpopulations of KaiC-bound KaiB is intimately linked to the KaiC phosphorylation cycle. These findings enrich our mechanistic understanding of the cyanobacterial clock and demonstrate the utility of EPR in elucidating circadian clock mechanisms.
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Affiliation(s)
- Gary K Chow
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Archana G Chavan
- School of Natural Sciences, University of California, Merced, California 95343, United States
| | - Joel Heisler
- Chemistry and Chemical Biology, University of California, Merced, California 95343, United States
| | - Yong-Gang Chang
- School of Natural Sciences, University of California, Merced, California 95343, United States
| | - Ning Zhang
- School of Natural Sciences, University of California, Merced, California 95343, United States
| | - Andy LiWang
- School of Natural Sciences, Chemistry and Biochemistry, Health Sciences Research Institute, and Center for Cellular and Biomolecular Machines, University of California, Merced, California 95343, United States.,Center for Circadian Biology, University of California, San Diego, La Jolla, California 92093, United States
| | - R David Britt
- Department of Chemistry, University of California, Davis, California 95616, United States
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7
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Martel A, Gabel F. Time-resolved small-angle neutron scattering (TR-SANS) for structural biology of dynamic systems: Principles, recent developments, and practical guidelines. Methods Enzymol 2022; 677:263-290. [DOI: 10.1016/bs.mie.2022.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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8
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Chavan AG, Swan JA, Heisler J, Sancar C, Ernst DC, Fang M, Palacios JG, Spangler RK, Bagshaw CR, Tripathi S, Crosby P, Golden SS, Partch CL, LiWang A. Reconstitution of an intact clock reveals mechanisms of circadian timekeeping. Science 2021; 374:eabd4453. [PMID: 34618577 DOI: 10.1126/science.abd4453] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Archana G Chavan
- School of Natural Sciences, University of California, Merced, CA 95343, USA
| | - Jeffrey A Swan
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
| | - Joel Heisler
- Department of Chemistry and Biochemistry, University of California, Merced, CA 95343, USA
| | - Cigdem Sancar
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Dustin C Ernst
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Mingxu Fang
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Joseph G Palacios
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
| | - Rebecca K Spangler
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
| | - Clive R Bagshaw
- 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
| | - Priya Crosby
- 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
| | - 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
| | - Andy LiWang
- School of Natural Sciences, University of California, Merced, CA 95343, USA.,Department of Chemistry and Biochemistry, University of California, Merced, CA 95343, USA.,Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA.,Center for Cellular and Biomolecular Machines, University of California, Merced, CA 95343, USA.,Health Sciences Research Institute, University of California, Merced, CA 95343, USA
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9
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Chow GK, Chavan AG, Heisler JC, Chang YG, LiWang A, Britt RD. Monitoring Protein-Protein Interactions in the Cyanobacterial Circadian Clock in Real Time via Electron Paramagnetic Resonance Spectroscopy. Biochemistry 2020; 59:2387-2400. [PMID: 32453554 PMCID: PMC7346098 DOI: 10.1021/acs.biochem.0c00279] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
![]()
The cyanobacterial circadian clock
in Synechococcus elongatus consists of three proteins,
KaiA, KaiB, and KaiC. KaiA and KaiB
rhythmically interact with KaiC to generate stable oscillations of
KaiC phosphorylation with a period of 24 h. The observation of stable
circadian oscillations when the three clock proteins are reconstituted
and combined in vitro makes it an ideal system for understanding its
underlying molecular mechanisms and circadian clocks in general. These
oscillations were historically monitored in vitro by gel electrophoresis
of reaction mixtures based on the differing electrophoretic mobilities
between various phosphostates of KaiC. As the KaiC phospho-distribution
represents only one facet of the oscillations, orthogonal tools are
necessary to explore other interactions to generate a full description
of the system. However, previous biochemical assays are discontinuous
or qualitative. To circumvent these limitations, we developed a spin-labeled
KaiB mutant that can differentiate KaiC-bound KaiB from free KaiB
using continuous-wave electron paramagnetic resonance spectroscopy
that is minimally sensitive to KaiA. Similar to wild-type (WT-KaiB),
this labeled mutant, in combination with KaiA, sustains robust circadian
rhythms of KaiC phosphorylation. This labeled mutant is hence a functional
surrogate of WT-KaiB and thus participates in and reports on autonomous
macroscopic circadian rhythms generated by mixtures that include KaiA,
KaiC, and ATP. Quantitative kinetics could be extracted with improved
precision and time resolution. We describe design principles, data
analysis, and limitations of this quantitative binding assay and discuss
future research necessary to overcome these challenges.
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Affiliation(s)
- Gary K Chow
- Department of Chemistry, University of California, Davis, California 95616, United States
| | | | | | | | - Andy LiWang
- Center for Circadian Biology, University of California, San Diego, La Jolla, California 92093, United States
| | - R David Britt
- Department of Chemistry, University of California, Davis, California 95616, United States
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10
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Koda SI, Saito S. An alternative interpretation of the slow KaiB-KaiC binding of the cyanobacterial clock proteins. Sci Rep 2020; 10:10439. [PMID: 32591637 PMCID: PMC7320175 DOI: 10.1038/s41598-020-67298-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 06/04/2020] [Indexed: 11/09/2022] Open
Abstract
The biological clock of cyanobacteria is composed of three proteins, KaiA, KaiB, and KaiC. The KaiB-KaiC binding brings the slowness into the system, which is essential for the long period of the circadian rhythm. However, there is no consensus as to the origin of the slowness due to the pre-binding conformational transition of either KaiB or KaiC. In this study, we propose a simple KaiB-KaiC binding scheme in a hexameric form with an attractive interaction between adjacent bound KaiB monomers, which is independent of KaiB's conformational change. We then show that the present scheme can explain several important experimental results on the binding, including that used as evidence for the slow conformational transition of KaiB. The present result thus indicates that the slowness arises from KaiC rather than KaiB.
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Affiliation(s)
- Shin-Ichi Koda
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, Aichi, 444-8585, Japan. .,School of Physical Sciences, The Graduate University for Advanced Studies, 38 Nishigo-Naka, Myodaiji, Okazaki, Aichi, 444-8585, Japan.
| | - Shinji Saito
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki, Aichi, 444-8585, Japan. .,School of Physical Sciences, The Graduate University for Advanced Studies, 38 Nishigo-Naka, Myodaiji, Okazaki, Aichi, 444-8585, Japan.
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11
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Partch CL. Orchestration of Circadian Timing by Macromolecular Protein Assemblies. J Mol Biol 2020; 432:3426-3448. [DOI: 10.1016/j.jmb.2019.12.046] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 12/13/2019] [Accepted: 12/18/2019] [Indexed: 12/13/2022]
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