Research from The University of Osaka finds that the protein at the heart of the cyanobacterial circadian clock is a self-contained, reliable, and robust timekeeper
Osaka, Japan – Almost all living things have an internal 24-hour clock which remains accurate regardless of temperature or other environmental changes. This clock is a highly sophisticated, yet simple, timekeeping mechanism that is critically important to many functions, including metabolism and survival. Until now, understanding the influences keeping the internal clock ticking reliability was unknown.
However, in a recent study published in
PNAS, researchers from The University of Osaka have revealed that circadian clock oscillation in cyanobacteria is controlled by factors intrinsic to one of the proteins that controls it, in a manner that is unaffected by environmental conditions.
Even the smallest, photosynthetic organisms have internal clocks, including cyanobacteria. These microorganisms are vital for aquatic environments, agriculture, and biotechnology. Given their vitality, it is even more important to ensure the correct timing of biological processes for photosynthesis during the day, and respiration at night.
Cyanobacteria are known to possess the simplest known circadian clock, involving only three primary proteins: KaiA, B, and C. It was these proteins that were the focus of the investigation.
“Though the cyanobacterial circadian clock is very simple, and can be reconstructed with three proteins, we still wanted to understand how these simple elements work together,” says lead author, Kumiko Ito-Miwa. “It is critical to understand how the reliability of the circadian rhythm is maintained under different environmental conditions, as it affects an incredibly wide variety of cellular processes.”
To do this, the researchers examined more than 20 mutations in the KaiC clock protein, with disturbed clock periods ranging from 15 to 60 hours. Through this, they were able to demonstrate that the circadian clock could maintain accurate timekeeping both
in vitro and
in vivo, regardless of environmental changes, through properties inherent to the clock proteins. This included the activity of ATPase, an enzyme responsible for producing chemical energy, which allows cells to perform their duties in various processes.
“The activity of this protein, which acts as the pacemaker of the cyanobacterial clock, did not change in response to different environmental conditions. This property, which appears to be innate to the protein itself, is likely critical for preserving circadian timing despite environmental changes,” explains Kumiko Ito-Miwa, lead author, building on a concept originally proposed and long pursued by Takao Kondo.
The findings suggest that the environment inside cyanobacterial cells may fine-tune the circadian clock to align it with Earth’s 24-hour cycle, offering significant insight into the fundamental question of how living organisms measure time.
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The article, “Intrinsic period stability of the cyanobacterial circadian oscillator
across in vitro and in vivo conditions,” was published in
PNAS at DOI:
https://doi.org/10.1073/pnas.2526714123
About The University of Osaka
The University of Osaka was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world. Now, The University of Osaka is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.
Website:
https://resou.osaka-u.ac.jp/en