1
|
Deng D, Meng H, Ma Y, Guo Y, Wang Z, He H, Xie W, Liu JE, Zhang L. The cumulative impact of temperature and nitrogen availability on the potential nitrogen fixation and extracellular polymeric substances secretion by Dolichospermum. HARMFUL ALGAE 2024; 135:102633. [PMID: 38830715 DOI: 10.1016/j.hal.2024.102633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 04/02/2024] [Accepted: 04/24/2024] [Indexed: 06/05/2024]
Abstract
Nitrogen-fixing cyanobacteria not only cause severe blooms but also play an important role in the nitrogen input processes of lakes. The production of extracellular polymeric substances (EPS) and the ability to fix nitrogen from the atmosphere provide nitrogen-fixing cyanobacteria with a competitive advantage over other organisms. Temperature and nitrogen availability are key environmental factors in regulating the growth of cyanobacteria. In this study, Dolichospermum (formerly known as Anabaena) was cultivated at three different temperatures (10 °C, 20 °C, and 30 °C) to examine the impact of temperature and nitrogen availability on nitrogen fixation capacity and the release of EPS. Initially, confocal laser scanning microscopy (CLSM) and the quantification of heterocysts at different temperatures revealed that lower temperatures (10 °C) hindered the differentiation of heterocysts under nitrogen-deprived conditions. Additionally, while heterocysts inhibited the photosynthetic activity of Dolichospermum, the secretion of EPS was notably affected by nitrogen limitation, particularly at 30 °C. Finally, real-time quantitative polymerase chain reaction (qPCR) was used to measure the expression of nitrogen-utilizing genes (ntcA and nifH) and EPS synthesis-related genes (wzb and wzc). The results indicated that under nitrogen-deprived conditions, the expression of each gene was upregulated, and there was a significant correlation between the upregulation of nitrogen-utilizing and EPS synthesis genes (P < 0.05). Our findings suggested that Dolichospermum responded to temperature variation by affecting the formation of heterocysts, impacting its potential nitrogen fixation capacity. Furthermore, the quantity of EPS released was more influenced by nitrogen availability than temperature. This research enhances our comprehension of interconnections between nitrogen deprivation and EPS production under the different temperatures.
Collapse
Affiliation(s)
- Dailan Deng
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing 210023, China
| | - Han Meng
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing 210023, China
| | - You Ma
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing 210023, China
| | - Yongqi Guo
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing 210023, China
| | - Zixuan Wang
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing 210023, China
| | - Huan He
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing 210023, China
| | - Wenming Xie
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing 210023, China
| | - Jin-E Liu
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Jiangsu Engineering Lab of Water and Soil Eco-remediation, Nanjing 210023, China.
| | - Limin Zhang
- School of Environment, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Nanjing Normal University, Nanjing 210023, PR China; Green Economy Development Institute, Nanjing University of Finance and Economics, Nanjing 210023, PR China
| |
Collapse
|
2
|
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.
Collapse
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.
| |
Collapse
|
3
|
Highly Sensitive Tryptophan Fluorescence Probe for detecting Rhythmic Conformational changes of KaiC in the Cyanobacterial Circadian Clock System. Biochem J 2022; 479:1505-1515. [PMID: 35771042 PMCID: PMC9342895 DOI: 10.1042/bcj20210544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 06/27/2022] [Accepted: 06/30/2022] [Indexed: 11/17/2022]
Abstract
KaiC, a core protein of the cyanobacterial circadian clock, consists of an N-terminal CI domain and a C-terminal CII domain, and assembles into a double-ring hexamer upon binding with ATP. KaiC rhythmically phosphorylates and dephosphorylates its own two adjacent residues Ser431 and Thr432 at the CII domain with a period of approximately 24h through assembly and disassembly with the other clock proteins, KaiA and/or KaiB. In this study, to understand how KaiC alters its conformation as the source of circadian rhythm, we investigated structural changes of an inner-radius side of the CII ring using time-resolved Trp fluorescence spectroscopy. A KaiC mutant harboring a Trp fluorescence probe at a position of 419 exhibited a robust circadian rhythm with little temperature sensitivity in the presence of KaiA and KaiB. Our fluorescence observations show a remarkable environmental change at the inner-radius side of the CII ring during circadian oscillation. Crystallographic analysis revealed that a side chain of Trp at the position of 419 was oriented toward a region undergoing a helix-coil transition, which is considered to be a key event to allosterically regulate the CI ring that plays a crucial role in determining the cycle period. The present study provides a dynamical insight into how KaiC generates circadian oscillation.
Collapse
|
4
|
Abstract
KaiC, a core clock protein in the cyanobacterial circadian clock system, hydrolyzes adenosine triphosphate (ATP) at two distinct sites in a slow but ordered manner to measure the circadian timescale. We used biochemical and structural biology techniques to characterize the properties and interplay of dual-adenosine triphosphatase (ATPase) active sites. Our results show that the N-terminal and C-terminal ATPases communicate with each other through an interface between the N-terminal and C-terminal domains in KaiC. The dual-ATPase sites are regulated rhythmically in a concerted or opposing manner dependent on the phase of the circadian clock system, controlling the affinities of KaiC for other clock proteins, KaiA and KaiB. KaiC is a dual adenosine triphosphatase (ATPase), with one active site in its N-terminal domain and another in its C-terminal domain, that drives the circadian clock system of cyanobacteria through sophisticated coordination of the two sites. To elucidate the coordination mechanism, we studied the contribution of the dual-ATPase activities in the ring-shaped KaiC hexamer and these structural bases for activation and inactivation. At the N-terminal active site, a lytic water molecule is sequestered between the N-terminal domains, and its reactivity to adenosine triphosphate (ATP) is controlled by the quaternary structure of the N-terminal ring. The C-terminal ATPase activity is regulated mostly by water-incorporating voids between the C-terminal domains, and the size of these voids is sensitive to phosphoryl modification of S431. The up-regulatory effect on the N-terminal ATPase activity inversely correlates with the affinity of KaiC for KaiB, a clock protein constitutes the circadian oscillator together with KaiC and KaiA, and the complete dissociation of KaiB from KaiC requires KaiA-assisted activation of the dual ATPase. Delicate interactions between the N-terminal and C-terminal rings make it possible for the components of the dual ATPase to work together, thereby driving the assembly and disassembly cycle of KaiA and KaiB.
Collapse
|
5
|
Furuike Y, Mukaiyama A, Ouyang D, Ito-Miwa K, Simon D, Yamashita E, Kondo T, Akiyama S. Elucidation of master allostery essential for circadian clock oscillation in cyanobacteria. SCIENCE ADVANCES 2022; 8:eabm8990. [PMID: 35427168 PMCID: PMC9012456 DOI: 10.1126/sciadv.abm8990] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Spatiotemporal allostery is the source of complex but ordered biological phenomena. To identify the structural basis for allostery that drives the cyanobacterial circadian clock, we crystallized the clock protein KaiC in four distinct states, which cover a whole cycle of phosphor-transfer events at Ser431 and Thr432. The minimal set of allosteric events required for oscillatory nature is a bidirectional coupling between the coil-to-helix transition of the Ser431-dependent phospho-switch in the C-terminal domain of KaiC and adenosine 5'-diphosphate release from its N-terminal domain during adenosine triphosphatase cycle. An engineered KaiC protein oscillator consisting of a minimal set of the identified master allosteric events exhibited a monophosphorylation cycle of Ser431 with a temperature-compensated circadian period, providing design principles for simple posttranslational biochemical circadian oscillators.
Collapse
Affiliation(s)
- Yoshihiko Furuike
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
- Corresponding author. (Y.F.); (S.A.)
| | - Atsushi Mukaiyama
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Dongyan Ouyang
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Kumiko Ito-Miwa
- Division of Biological Science, Graduate School of Science and Institute for Advanced Studies, Nagoya University, Nagoya 464-8602, Japan
| | - Damien Simon
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Eiki Yamashita
- Institute for Protein Research, Osaka University, 3-2 Yamada-oka, Suita 565-0871, Japan
| | - Takao Kondo
- Division of Biological Science, Graduate School of Science and Institute for Advanced Studies, Nagoya University, Nagoya 464-8602, Japan
| | - Shuji Akiyama
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
- Corresponding author. (Y.F.); (S.A.)
| |
Collapse
|
6
|
Simon D, Mukaiyama A, Furuike Y, Akiyama S. Slow and temperature-compensated autonomous disassembly of KaiB–KaiC complex. Biophys Physicobiol 2022; 19:1-11. [PMID: 35666689 PMCID: PMC9135616 DOI: 10.2142/biophysico.bppb-v19.0008] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 03/28/2022] [Indexed: 12/01/2022] Open
Affiliation(s)
- Damien Simon
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences
| | - Atsushi Mukaiyama
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences
| | - Yoshihiko Furuike
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences
| | - Shuji Akiyama
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institutes of Natural Sciences
| |
Collapse
|
7
|
Real-Time In Vitro Fluorescence Anisotropy of the Cyanobacterial Circadian Clock. Methods Mol Biol 2021. [PMID: 33284432 DOI: 10.1007/978-1-0716-0381-9_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Stochastic diffusion of a solution of fluorophores after photoselection reduces the polarization of emission, or fluorescence anisotropy. Because this randomization process is slower for larger molecules, fluorescence anisotropy is effective for measuring the kinetics of protein-binding events. Here, we describe how to use the technique to carry out real-time observations in vitro of the cyanobacterial circadian clock.
Collapse
|
8
|
Ouyang D, Furuike Y, Mukaiyama A, Ito-Miwa K, Kondo T, Akiyama S. Development and Optimization of Expression, Purification, and ATPase Assay of KaiC for Medium-Throughput Screening of Circadian Clock Mutants in Cyanobacteria. Int J Mol Sci 2019; 20:ijms20112789. [PMID: 31181593 PMCID: PMC6600144 DOI: 10.3390/ijms20112789] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 05/23/2019] [Accepted: 06/03/2019] [Indexed: 11/16/2022] Open
Abstract
The slow but temperature-insensitive adenosine triphosphate (ATP) hydrolysis reaction in KaiC is considered as one of the factors determining the temperature-compensated period length of the cyanobacterial circadian clock system. Structural units responsible for this low but temperature-compensated ATPase have remained unclear. Although whole-KaiC scanning mutagenesis can be a promising experimental strategy, producing KaiC mutants and assaying those ATPase activities consume considerable time and effort. To overcome these bottlenecks for in vitro screening, we optimized protocols for expressing and purifying the KaiC mutants and then designed a high-performance liquid chromatography system equipped with a multi-channel high-precision temperature controller to assay the ATPase activity of multiple KaiC mutants simultaneously at different temperatures. Through the present protocol, the time required for one KaiC mutant is reduced by approximately 80% (six-fold throughput) relative to the conventional protocol with reasonable reproducibility. For validation purposes, we picked up three representatives from 86 alanine-scanning KaiC mutants preliminarily investigated thus far and characterized those clock functions in detail.
Collapse
Affiliation(s)
- Dongyan Ouyang
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institute for Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
| | - Yoshihiko Furuike
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institute for Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
| | - Atsushi Mukaiyama
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institute for Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
| | - Kumiko Ito-Miwa
- Division of Biological Science, Graduate School of Science and Institute for Advanced Research, Nagoya University; Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
| | - Takao Kondo
- Division of Biological Science, Graduate School of Science and Institute for Advanced Research, Nagoya University; Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
| | - Shuji Akiyama
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institute for Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
| |
Collapse
|
9
|
Heisler J, Chavan A, Chang YG, LiWang A. Real-Time In Vitro Fluorescence Anisotropy of the Cyanobacterial Circadian Clock. Methods Protoc 2019; 2:E42. [PMID: 31164621 PMCID: PMC6632157 DOI: 10.3390/mps2020042] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2019] [Revised: 05/20/2019] [Accepted: 05/22/2019] [Indexed: 11/24/2022] Open
Abstract
Uniquely, the circadian clock of cyanobacteria can be reconstructed outside the complex milieu of live cells, greatly simplifying the investigation of a functioning biological chronometer. The core oscillator component is composed of only three proteins, KaiA, KaiB, and KaiC, and together with ATP they undergo waves of assembly and disassembly that drive phosphorylation rhythms in KaiC. Typically, the time points of these reactions are analyzed ex post facto by denaturing polyacrylamide gel electrophoresis, because this technique resolves the different states of phosphorylation of KaiC. Here, we describe a more sensitive method that allows real-time monitoring of the clock reaction. By labeling one of the clock proteins with a fluorophore, in this case KaiB, the in vitro clock reaction can be monitored by fluorescence anisotropy on the minutes time scale for weeks.
Collapse
Affiliation(s)
- Joel Heisler
- Chemistry & Chemical Biology, University of California, Merced, CA 95343, USA.
- Center for Cellular and Biomolecular Machines, University of California, Merced, CA 95343, USA.
| | - Archana Chavan
- School of Natural Sciences, University of California, Merced, CA 95343, USA.
| | - Yong-Gang Chang
- School of Natural Sciences, University of California, Merced, CA 95343, USA.
| | - Andy LiWang
- Chemistry & Chemical Biology, University of California, Merced, CA 95343, USA.
- Center for Cellular and Biomolecular Machines, 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.
- Quantitative & Systems Biology, University of California, Merced, CA 95343, USA.
- Health Sciences Research Institute, University of California, Merced, CA 95343, USA.
| |
Collapse
|
10
|
Mukaiyama A, Ouyang D, Furuike Y, Akiyama S. KaiC from a cyanobacterium Gloeocapsa sp. PCC 7428 retains functional and structural properties required as the core of circadian clock system. Int J Biol Macromol 2019; 131:67-73. [PMID: 30857964 DOI: 10.1016/j.ijbiomac.2019.03.051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 03/07/2019] [Indexed: 11/25/2022]
Abstract
KaiC, the core protein of the cyanobacterial clock, assembles into a hexamer upon ATP-binding. The hexameric KaiC from a cyanobacterium Synechococcus elongatus PCC 7942 (Se-KaiC) is a multifunctional enzyme with autokinase, autophosphatase and ATPase and these activities show a circadian rhythm in the presence of two other clock proteins, KaiA and KaiB both in vivo and in vitro. While an interplay among three enzymatic activities has been pointed out through studies on Se-KaiC as the basis of circadian rhythmicity in cyanobacteria, little is known about the structure and functions of KaiC from other cyanobacterial species. In this study, we established a protocol to prepare KaiC from Gloeocapsa sp. PCC 7428 (Gl-KaiC) belonging to a distinct genus from Synechococcus and characterized its oligomeric structure and function. The results demonstrate that Gl-KaiC shares the basic properties with Se-KaiC. The present protocol offers practical means for further analysis of structure and function of Gl-KaiC, which would provide insights into diversity and evolution of the clock systems in cyanobacteria.
Collapse
Affiliation(s)
- Atsushi Mukaiyama
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institute for Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan; Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Dongyan Ouyang
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institute for Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Yoshihiko Furuike
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institute for Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan; Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Shuji Akiyama
- Research Center of Integrative Molecular Systems (CIMoS), Institute for Molecular Science, National Institute for Natural Sciences, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan; Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
| |
Collapse
|
11
|
Conformational rearrangements of the C1 ring in KaiC measure the timing of assembly with KaiB. Sci Rep 2018; 8:8803. [PMID: 29892030 PMCID: PMC5995851 DOI: 10.1038/s41598-018-27131-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 05/25/2018] [Indexed: 01/26/2023] Open
Abstract
KaiC, the core oscillator of the cyanobacterial circadian clock, is composed of an N-terminal C1 domain and a C-terminal C2 domain, and assembles into a double-ring hexamer upon ATP binding. Cyclic phosphorylation and dephosphorylation at Ser431 and Thr432 in the C2 domain proceed with a period of approximately 24 h in the presence of other clock proteins, KaiA and KaiB, but recent studies have revealed a crucial role for the C1 ring in determining the cycle period. In this study, we mapped dynamic structural changes of the C1 ring in solution using a combination of site-directed tryptophan mutagenesis and fluorescence spectroscopy. We found that the C1 ring undergoes a structural transition, coupled with ATPase activity and the phosphorylation state, while maintaining its hexameric ring structure. This transition triggered by ATP hydrolysis in the C1 ring in specific phosphorylation states is a necessary event for recruitment of KaiB, limiting the overall rate of slow complex formation. Our results provide structural and kinetic insights into the C1-ring rearrangements governing the slow dynamics of the cyanobacterial circadian clock.
Collapse
|