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Workings of the circadian clock
March 4, 2018, 1:26 pm

Circadian clocks are found in most living species including microbes and bacteria, plants and insects, animals and humans. The workings of these clocks, which are believed to have been an adaptation over millennia to dramatic swings in daylight hours and temperature caused by the Earth's rotation, are still not fully understood.

Now researchers at the University of California, studying circadian clock in spirulina, a cyanobacteria, have discovered that how proteins move hour by hour is central to how the bacteria’s circadian clock functions. Spirulina is rich in vitamins and minerals and is often used as natural food dye for candy and gum

Cyanobacterial circadian clock proteins are unique because they can be reconstituted within a test tube in the absence of live cells. Researchers made a solution of these proteins and adenosine triphosphate (ATP), the food for the proteins, to create a circadian clock that functioned for weeks.

Using nuclear magnetic resonance (NMR) spectroscopy, which helps study the protein structure and dynamics of biological molecules, and X-ray crystallography — a technique used to capture static structures of proteins and their complexes at atomic and near-atomic resolution —the researchers were able to study the structures to gain greater insights into their function.

Cyanobacterial clock proteins are not exactly the same as the clock proteins of animals or human clocks, but proteins serve as the cogs, gears and springs of all circadian clockworks and the overall function of the proteins is similar. Because clock proteins need to keep time, there should be some basic principles of biological timekeeping shared between all clocks regardless of whether the proteins are the same or not.

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