Researchers at IMS, Japan dissolved the mechanism of circadian clocks little depending on the temperature change. By using the cyanobacterial clock protein, KaiC, and the specialized neutron scattering method, they found that the overall architecture of the clock protein is the key to compensate the structural influence induced by the temperature change.
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A wide range of organisms belonging to bacteria, insects, plants and mammals possess biological time-keeping systems called circadian clocks. The biochemical reactions of clock proteins generate the circadian rhythms governing cellular activities. In general, chemical reactions are accelerated at higher temperatures. This is based on the natural law that atoms and molecules move more rapidly at high temperatures. However, the clock’s oscillatory period is independent of the ambient temperature which changes along with the day-night transition. The temperature compensation mechanisms of the clock systems have not been understood so far.
The circadian clock of cyanobacteria (or blue-green algae) is driven by the ATP hydrolysis reaction of KaiC, a core clock protein. As its activity is almost constant in the wide temperature range, KaiC has a function to sense the temperature and compensate its influence. The clock system can be reconstituted in a test tube by mixing KaiC and two other proteins, KaiA and KaiB. Cyclic assembly and disassembly of these three proteins occur in a circadian manner. The period of the oscillation is also temperature-compensated. Researchers attempted to solve the mystery of the temperature compensation by detecting atomic and molecular dynamics of KaiC.
Group of researchers led by Prof. Shuji Akiyama and Assist. Prof. Yoshihiko Furuike, biophysicists at Institute for Molecular Science, has identified KaiC that lose the temperature compensation ability. They compared the behavior of the native and mutant KaiC by a quasi-elastic neutron scattering method. The advanced experimental station, J-PARC BL02, allowed them to observe the rapid motion of hydrogen atoms uniformly included in proteins and the relatively slow motion of overall structure of proteins.
The results showed that the temperature compensation of KaiC does not originate from the atomic dynamics, but from the molecular architecture. The rapid and local motion of atoms was accelerated by increasing temperature in both native and mutant KaiC. On the other hand, the relatively slow motion of KaiC entire structure was modulated by the mutation. The researchers will expand their research to find out whether clock proteins from other species exhibit characteristics similar to KaiC.
Information of the paper
Journal name: Communications Physics
Title: Cross-scale analysis of temperature compensation in the cyanobacterial circadian clock system
Authors: Yoshihiko Furuike, Dongyan Ouyang, Taiki Tominaga, Tatsuhito Matsuo, Atsushi Mukaiyama, Yukinobu Kawakita, Satoru Fujiwara, Shuji Akiyama
DOI: 10.1038/s42005-022-00852-z
Financial support
Grants-in-aid for Scientific Research (17H06165, etc.)
Contact Person
Shuji Akiyama
TEL: +81-564-55-7363
E-mail: akiyamas_at_ims.ac.jp
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