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For the very first time researchers have identified the molecular structure of a protein complex that plays an important role in regulating the circadian rhythm. The discovery is being considered as an important progress towards better understanding the functioning of the circadian clock. 

The circadian clock, also known as inner clock, is responsible for coordinating the sleep-wake rhythm and many other body processes. 

"Our circadian clock controls many important physiological functions," explained the lead researcher Professor Eva Wolf in the press release. 

In case the natural rhythm is disrupted, i.e, in the case of people on shift work, likelihood of developing metabolic disorders, diabetes or even cancer is significantly increased. 

Researchers did the x-ray analysis of the cryptochrome-period complex structure which enabled them to observe the atomic details of the interaction between the cryptochrome and period proteins. They also discovered that the zinc ion mediates this interaction. 

"The metal ion stabilizes the complex and also appears to influence an adjacent disulfide bond," clarified Wolf.

The researchers had not expected to detect a disulfide bond in the presence of the redox state that prevails in the cytoplasm and the cell nucleus. Its existence is probably regulated by the zinc ion and the disulfide bond itself is perhaps a sensor that indicates the metabolic status of the cell, the release added. 

"We assume that the formation of this cryptochrome-period protein complex provides a mechanism by which the circadian clock interacts with the metabolism, while the zinc ion and the disulfide bond play an important role in regulating the stability of the complex," summarized Wolf in the press release. 

The research has been published in the journal Cell.