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: Vietnam's taste for cat leaves pets in peril

add to favorites email to friend print save as pdf

Related Stories

Keeping time: Circadian clocks

Oct 02, 2012

Our planet was revolving on its axis, turning night into day every 24 hours, for 4.5 billion years - long before any form of life existed here. About a billion years later, the very first simple bacterial ...

Researchers better understand biological clock

Oct 12, 2007

Researchers at Harvard University and the Howard Hughes Medical Institute (HHMI) have discovered that a simple circadian clock found in some bacteria operates by the rhythmic addition and subtraction of phosphate groups at ...

Recommended for you

Vietnam's taste for cat leaves pets in peril

39 minutes ago

The enduring popularity of "little tiger" as a snack to accompany a beer in Vietnam means that cat owners live in constant fear of animal snatchers, despite an official ban.

New species of mayfly discovered in India

2 hours ago

Scientists have discovered a new species of mayfly in the southern Western Ghats, a mountain range along the west coast of India. In fact, this is the first time that any mayfly belonging to the genus Labiobaetis has be ...

Giant anteaters kill two hunters in Brazil

Jul 26, 2014

Giant anteaters in Brazil have killed two hunters in separate incidents, raising concerns about the animals' loss of habitat and the growing risk of dangerous encounters with people, researchers said.

Rising temperatures can be hard on dogs

Jul 25, 2014

The "dog days of summer" are here, but don't let the phrase fool you. This hot time of year can be dangerous for your pup, says a Kansas State University veterinarian.

User comments : 0