Science Current Events | Science News | Brightsurf.com
 
Email a Friend Send to a friend
Printer Friendly Print Simplest circadian clocks operate via orderly phosphate transfers

Simplest circadian clocks operate via orderly phosphate transfers

October 05, 2007

3 proteins in a test tube, fueled by ATP, maintain accurate circadian rhythm for weeks

CAMBRIDGE, Mass. -- Researchers at Harvard University and the Howard Hughes Medical Institute have found that a simple circadian clock found in some bacteria operates by the rhythmic addition and subtraction of phosphate groups at two key locations on a single protein. This phosphate pattern is influenced by two other proteins, driving phosphorylation to oscillate according to a remarkably accurate 24-hour cycle.




Writing this week in the journal Science, the scientists describe what causes a trio of proteins, if placed in a test tube with the common biochemical fuel ATP as a source of phosphate, to function as a minimalist biological clock of sorts, maintaining an accurate circadian rhythm for long periods of time.

The new Harvard work builds upon research reported in 2005 by biologist Takao Kondo and colleagues at Nagoya University in Japan. That team initially reported that a circadian clock could be reconstituted in a test tube solely with three proteins and ATP.

"The most striking feature of this circadian oscillator is its precision," says Erin K. O'Shea, professor of molecular and cellular biology and chemistry and chemical biology in Harvard's Faculty of Arts and Sciences (FAS), director of the FAS Center for Systems Biology, and Howard Hughes Medical Institute investigator. "Even in the absence of external cues -- in total darkness -- these minuscule protein-based clocks can maintain precision to a small fraction of a day over several weeks."

O'Shea, postdoctoral researcher Michael J. Rust, graduate student Joseph S. Markson, and colleagues studied circadian rhythms in cyanobacteria, better known as blue-green algae. These simple organisms, responsible for some 70 percent of the Earth's photosynthesis, devote most of their energies toward just two biological processes: photosynthesis and reproduction.

The scientists scrutinized the activity of three bacterial proteins known as KaiA, KaiB, and KaiC. They found that during the daytime, KaiC is cyclically phosphorylated at two amino acid residues: first at a specific threonine, and then at a specific serine. During nighttime hours, the two amino acids are dephosphorylated in the same order.

The KaiA protein promotes the phosphorylation of KaiC, and KaiB, sensing one of the phosphorylated forms of KaiC, blocks KaiA's activity, creating an intricate biochemical dance that results in a nearly perfect 24-hour oscillation. The researchers' subsequent mathematical analysis confirmed that this distinctive dynamic would, in fact, reproduce a circadian period.

The bacterial proteins studied by O'Shea, Rust, Markson, and colleagues are not known to exist in humans, but the researchers say their findings illuminate general feedback mechanisms that could serve to establish chronological oscillations in a whole host of organisms.

"It's unknown whether such a mechanism is at the core of all circadian clocks," says Rust, a postdoctoral researcher in Harvard's Department of Molecular and Cellular Biology. "It's the simplest chemical oscillator known, and we are looking at it as a possible model for other species."

O'Shea says the 2005 finding by Kondo and colleagues that a cyanobacterial circadian clock could be recreated in a test tube using only three proteins and ATP surprised researchers because it showed that some circadian rhythms are driven solely by protein-protein interactions.

"It demonstrated that circadian clocks can operate independently of DNA and most cellular components, contradicting the previous prevailing theory that an entire organism was likely needed to maintain a clock," she says.

Harvard University



Related Circadian Clock Current Events and Circadian Clock News Articles Circadian Clock Current Events and Circadian Clock News RSS Circadian Clock Current Events and Circadian Clock News RSS
Circadian surprise: A heat sensor for body-clock synchronization
New research on the fruit-fly brain points to a possible mechanism by which temperature influences the body clock, according to scientists from Queen Mary, University of London.

U-M discovery about biological clocks overturns long-held theory
University of Michigan mathematicians and their British colleagues say they have identified the signal that the brain sends to the rest of the body to control biological rhythms, a finding that overturns a long-held theory about our internal clock.

Plants' internal clock can improve climate-change models
The ability of plants to tell the time, a mechanism common to all living beings, enables them to survive, grow and reproduce.

MicroRNAs grease the cell's circadian clockwork
Most of our cells possess an internal clock, a group of genes displaying a cyclic expression pattern that reaches a peak once a day.

A Biological Basis for the 8-Hour Workday?
The circadian clock coordinates physiological and behavioral processes on a 24-hour rhythm, allowing animals to anticipate changes in their environment and prepare accordingly. Scientists already know that some genes are controlled by the clock and are turned on only one time during each 24-hour cycle.

Scripps research scientists model 3D structures of proteins that control human clock
In an Early Edition issue of The Proceedings of the National Academy of Sciences (PNAS) on April 9, 2009, the researchers report that they have been able to determine the molecular structure of a plant photolyase protein that is surprisingly similar to two cryptochrome proteins that control the "master clock" in humans and other mammals.

Missing or mutated 'clock' gene linked to vascular disease
The circadian clocks that set the rhythmic motion of our bodies for wakeful days and sleepy nights can also set us up for vascular disease when broken, Medical College of Georgia researchers say.

UNC study: Tinkering with the circadian clock can suppress cancer growth
Researchers at the University of North Carolina at Chapel Hill have shown that disruption of the circadian clock - the internal time-keeping mechanism that keeps the body running on a 24-hour cycle - can slow the progression of cancer.

UNC study supports role of circadian clock in response to chemotherapy
For years, research has hinted that the time of day that cancer patients receive chemotherapy can impact their chances of survival. But the lack of a clear scientific explanation for this finding has kept clinicians from considering timing as a factor in treatment.

Bright lights, not-so-big pupils
A team of Johns Hopkins neuroscientists has worked out how some newly discovered light sensors in the eye detect light and communicate with the brain. The report appears online this week in Nature.
More Circadian Clock Current Events and Circadian Clock News Articles
Circadian Clock

Circadian Clock
Scarring Fields (Primary Contributor)



Rhythms of Life: The Biological Clocks that Control the Daily Lives of Every Living Thing

Rhythms of Life: The Biological Clocks that Control the Daily Lives of Every Living Thing
by Russell G. Foster (Author), Leon Kreitzman (Author)

Why can’t teenagers get out of bed in the morning? How do bees tell the time? Why do some plants open and close their flowers at the same time each day? Why do so many people suffer the misery of jet lag? In this fascinating book, Russell Foster and Leon Kreitzman explain the significance of the biological clock, showing how it has played an essential role in evolution and why it continues to play a vitally important role in all living organisms.

The authors tell us that biological clocks are embedded in our genes and reset at sunrise and sunset each day to link astronomical time with an organism’s internal time. They discuss how scientists are working out the clockwork mechanisms and what governs them, and they describe how organisms measure different intervals of time, how...

  Circadian Clocks
by The Jarts



BioBrite Sunrise Radio Advanced Model - Platinum with 2 FREE replacement bulbs

BioBrite Sunrise Radio Advanced Model - Platinum with 2 FREE replacement bulbs
by BioBrite

BioBrite's newest product, the SunRise Clock Radio is derived from medical research on light and human behavior. In the early morning, the human biological clock is sensitive to low intensity light. So, waking to a slowly increasing light can result in a smoother, more natural transition to wakefulness. While gently waking with a simulated sunrise, now you can let the 6:52 weather report on the FM radio inform you of a sunny day before you even open your eyes. If you'd like to fall asleep with music playing in the background, you can program the radio to fade out after a period of time which you can adjust. Other features include the choice of fade up and fade down over 15, 30, 45, or 60 minutes; snooze feature; the security feature of random evening lighting; fade to nightlight; a back...

Clockwork Genes: Discoveries in Biological Time

Clockwork Genes: Discoveries in Biological Time
Also With: Micahel Rosbash (Primary Contributor), Joseph S. Takahshi (Primary Contributor)

The Sun Rises and sets, tides ebb and flow, and the seasons change. Circadian clocks -- internal timekeepers that govern fluctuations in behavior and physiology on a 24-hour cycle -- have helped organisms adapt to the rhythms of life on Earth.

In recent years, scientists have gained a greater understanding of circadian clocks. These four lectures highlight the research of two biomedical scientists who have made groundbreaking discoveries elucidating the molecular basis of circadian clocks.

In these lectures -- enhanced by scientific animations and student questions -- the scientists explain what circadian clocks are, how they work, and what relevance this knowledge might have for human health. They also describe the scientific methods that led to their...

Circadian Clocks

Circadian Clocks
The Jarts (Primary Contributor)



Handbook of Behavioral Neurobiology, Volume 12: Circadian Clocks (Handbooks of Behavioral Neurobiology)

Handbook of Behavioral Neurobiology, Volume 12: Circadian Clocks (Handbooks of Behavioral Neurobiology)
by Joseph S. Takahashi (Editor), Fred W. Turek (Editor), Robert Y. Moore (Editor)

The Handbook of Behavioral Neurobiology series deals with the aspects of neurosciences that have the most direct and immediate bearing on behavior. It presents the most current research available in the specific areas of sensory modalities. This volume explores circadian rhythms.

Internal Clock

Internal Clock
Circadian Rhythms (Primary Contributor)



  Circadian Clocks: Proceedings of the Feldafing Summer School 7-18 September 1964
by Jurgen (editor) Aschoff (Author)



The Daily Ground

The Daily Ground
Circadian Rhythms (Primary Contributor)



© 2009 BrightSurf.com