New research provides dynamic visualization of simplest circadian clock

Mar 13, 2008

Scientists have acquired a more dynamic picture of events that underlie the functions of a bacterial biological clock. New research published online March 13th by Cell Press in the journal Molecular Cell, shows how the simplest organism known to have a circadian clock keeps time and may enhance our understanding of how other organisms establish and govern chronological rhythms.

A variety of organisms have evolved endogenous timing systems called a circadian clock that allows them to regulate metabolic activities in a day/night cycle. The simplest organisms known to possess a circadian oscillator are the cyanobacteria, better known as blue-green algae. The essential components of the circadian oscillator in cyanobacteria are the three clock proteins KaiA, KaiB and KaiC, all of which are expressed in the cyanobacterium S. elongatus.

Considerable research has implicated the phosphorylation cycle of KaiC as the central pacemaker in cyanobacteria and has demonstrated that the Kai proteins are repeatedly assembled and disassembled into heteromultimeric complexes, termed periodosomes. The crystal structure of each clock protein has also been determined and analyzed.

“Despite the substantial progress in structural characterization, the relationship between the assembly/disassembly dynamics and the circadian phosphorylation of KaiC is still poorly understood, mainly because of the difficulty in unraveling the underlying mechanisms solely from the static molecular pictures of individual clock components,” explains Dr. Akiyama from the Japan Science and Technology Agency.

To obtain a more complete visualization of the cyanobacterial circadian oscillator, Dr. Akiyama and colleagues used small-angle X-ray scattering (SAXS) to follow the assembly/disassembly dynamics of the S. elongatus heteromultimeric Kai complexes in real time. The researchers found that the assembly/disassembly processes are crucial for phase entrainment in the early synchronizing stage but are passively driven by the phosphorylation status of KaiC in the late oscillatory stage. Further, KaiA and KaiB are recruited to KaiC in a phosphorylation-dependent manner.

“Our findings demonstrate that the initial phase of the cyanobacterial oscillator is determined predominantly by the assembly/disassembly communication of the clock components, and that the period is essentially resistant to intracellular noise such as collisions, cytoplasmic viscosity and crowding. These resistances are achieved in the binary and ternary complexes by recruiting KaiA homodimers, KaiB homotetramers and KaiC homohexamers in a phosphorylation-dependent manner,” concludes Dr. Akiyama.

Source: Cell Press

Explore further: China crushes half a tonne of ivory in symbolic gesture

Related Stories

Architects to hatch Ecocapsule as low-energy house

8 hours ago

Where people call home depends on varied factors, from poverty level to personal philosophy to vanity to community pressure. Ecocapsule appears to be the result of special factors, a team of architects applying ...

California farmers agree to drastically cut water use

11 hours ago

California farmers who hold some of the state's strongest water rights avoided the threat of deep mandatory cuts when the state accepted their proposal to voluntarily reduce consumption by 25 percent amid ...

Apple may deliver ways to rev up the iPad, report says

11 hours ago

MacRumors last month said that the latest numbers from market research firm IDC's Worldwide Quarterly Tablet Tracker revealed Apple stayed on as the largest vendor in a declining tablet market. The iPad ...

Recommended for you

Godwits are flexible... when they get the chance

5 hours ago

Black-tailed godwits are able to cope with unpredictable weather. This was revealed by a thorough analysis of the extraordinary spring of 2013 by ecologist Nathan Senner of the University of Groningen and ...

Rules aim to protect imperiled bird's habitat in 10 states

12 hours ago

Interior Secretary Sally Jewell revealed plans Thursday to preserve habitat in 10 Western states for an imperiled ground-dwelling bird, the federal government's biggest land-planning effort to date for conservation of a single ...

Understanding how cells follow electric fields

13 hours ago

Many living things can respond to electric fields, either moving or using them to detect prey or enemies. Weak electric fields may be important growth and development, and in wound healing: it's known that ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.