Unlocking complex workings of the biological clock
Research team reveals what drives the circadian rhythms in cyanobacteria
Date:
April 18, 2022
Source:
National Institutes of Natural Sciences
Summary:
Scientists want to increase their understanding of circadian
rhythms, those internal 24-hour biological clock cycles of sleeping
and waking that occur in organisms, ranging from humans to plants to
fungi to bacteria. Researchers have examined the complex workings
of cyanobacteria and can now better comprehend what drives its
circadian clock.
FULL STORY ========================================================================== Scientists want to increase their understanding of circadian rhythms,
those internal 24-hour biological clock cycles of sleeping and waking that occur in organisms, ranging from humans to plants to fungi to bacteria. A research team has examined the complex workings of cyanobacteria and
can now better comprehend what drives its circadian clock.
==========================================================================
The team, led by researchers from the Institute for Molecular Science,
National Institutes of Natural Sciences in Okazaki, Japan, published
their findings on 15th April 2022 in Science Advances.
The team focused their research on KaiC, the clock protein that regulates
the circadian rhythm in cyanobacteria, a type of bacteria lives in all
types of water and are often found in blue-green algae. These biological
clocks in organisms are composed of proteins. The cyanobacterial
circadian clock is the simplest circadian clock as far as the number of
its components, yet it is still a very complex system that can provide scientists with clues to the working of all circadian clocks. The blueish cyanobacteria are microorganisms that can be found in environments
ranging from salt and fresh waters to soils to rocks. The team examined
the structural basis for allostery, the complex changes that occur in
shape and activity of the KaiC protein in the cyanobacteria. Allostery
drives the cyanobacterial circadian clock.
The team studied the atomic structures of the KaiC clock protein,
by screening thousands of crystallization conditions. This detailed
study of the atomic structures allowed them to cover the overall phosphorylation cycle, that process where a phosphate is transferred to
the protein. Phosphorylation cooperates with another reaction cycle,
ATP hydrolysis, which is the energy consuming events determining the
clock speed. The phosphorylation-ATP hydrolysis system works like a
regulator for the cell activity. To help them understand the basis for the allostery, they crystallized the KaiC protein in eight distinct states, allowing them to observe the cooperativity between the phosphorylation
cycle and the ATP hydrolysis cycle working like two gears.
In the past, scientists have studied the phosphorus cycle of the KaiC
protein in vivio, in vitro, and in silico. Yet little was known about
how allostery regulates the phosphorus cycle in KaiC.
By studying the KaiC in the eight distinct states, the team was able to
observe a coupling that occurs in the phosphorus cycle and the ATPase hydrolysis cycle.
This coupling of the two gears drives the cyanobacterial circadian clock.
"Because proteins are composed of a vast number of atoms, it is not
easy to understand the mechanisms of their complicated but ordered
functions. We need to trace the structural changes of proteins patiently,"
said Yoshihiko Furuike, assistant professor at the Institute for Molecular Science, National Institutes of Natural Sciences.
The KaiC protein rhythmically activates and inactivates the reaction
cycles autonomously to regulate assembly states of other clock-related proteins. So thinking about their next steps, the team might use
structural biology to reveal the atomic mechanisms of acceleration and deceleration of the gear rotations. "Our goal is to see all cyanobacterial clock proteins during the oscillation at an atomic level and to describe
the moment that the ordered rhythm arises from chaotic atomic dynamics," Furuike said.
Their work can serve as a research tool, helping scientists to
better understand the mechanisms at work in the circadian clock
cycle. Looking ahead, the research team can see their findings having
wider applications. Mammals, insects, plants, and bacteria all have their
own clock proteins with distinct sequences and structures. "However, the
logic behind the relationship between KaiC dynamics and clock functions
can be applied to other studies on various organisms," Furuike said.
Paper authors include Yoshihiko Furuike, Shuji Akiyama, Institute for
Molecular Science, National Institutes of Natural Sciences, Okazaki,
Japan. In addition to the researchers from the Institute for Molecular
Science, others on the team include researchers from SOKENDAI, The
Graduate University for Advanced Studies; Graduate School of Science and Institute for Advanced Studies, Nagoya University; and the Institute for Protein Research, Osaka University. Their work was funded by Grants-in-Aid
for Scientific Research.
========================================================================== Story Source: Materials provided by
National_Institutes_of_Natural_Sciences. Note: Content may be edited
for style and length.
========================================================================== Journal Reference:
1. Yoshihiko Furuike, Atsushi Mukaiyama, Dongyan Ouyang, Kumiko
Ito-Miwa,
Damien Simon, Eiki Yamashita, Takao Kondo, Shuji
Akiyama. Elucidation of master allostery essential for circadian
clock oscillation in cyanobacteria. Science Advances, 2022; 8 (15)
DOI: 10.1126/sciadv.abm8990 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220415163757.htm
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