Researchers discover turbo switch of calcium pump in biological cells

Oct 21, 2012
This shows the structure of the calcium pump switch in cells of the plant thale cress (Arabidopsis thaliana). Credit: Henning Tidow et al.; University of Aarhus

When animals and plants are exposed to influences such as bacterial attack, odour and cold, calcium ions flow into the cells. The calcium provides the cells with a signal about what is going on outside, but as high concentrations of calcium are toxic to the cells, it must be quickly pumped out again. Researchers from the Danish National Research Foundation's PUMPkin Centre at both the University of Copenhagen and Aarhus University have now shown that calcium pumps in the cell's outer membrane adjust the pump speed very accurately to the calcium concentration. These findings have just been published in the journal Nature.

The calcium pump is located in the that surrounds the cells of humans, animals and plants. Leading researchers from Aarhus University and the University of Copenhagen have now provided new information of how the calcium pump regulates the amount of calcium in the cells. This amount is critical to the health and survival of the cell.

"It turns out that the calcium pump can accurately measure the cell's calcium content and adjust its speed in accordance with this information. This prevents the concentration of calcium ions in the from reaching a critical concentration that damages the cells. The calcium pump is inactive when the concentration of calcium is low, but it is activated stepwise when the increases," say Postdoctoral Fellows Henning Tidow and Lisbeth Rosager Poulsen, who took part in the joint research project.

The researchers' starting point was the calcium pump located in the of the thale cress (), but the also applies to the corresponding calcium pump in humans and animals.

Previous studies have shown that calcium pumps in both animals and plants work together with a protein called calmodulin. When there are many calcium ions in a cell, some of these bind to calmodulin, which is thereby able to activate the calcium pump.

"We purified the part of the calcium pump that interacts with calcium-activated calmodulin, and we managed to crystallise a protein complex. To our great surprise, we found that the calcium pump binds two calmodulin proteins, and not just one as always assumed," explains Dr Tidow.

This shows crystallized samples of the calcium pump complex of thale cress (Arabidopsis thaliana). Credit: Henning Tidow, University of Aarhus

The fact that two calmodulin proteins are involved in the regulation of the calcium pump activity means that the calcium pump has three steps. It is switched off when no calcium-activated calmodulin is bound, it pumps at medium speed when binding occurs at one calmodulin protein, and it pumps at full speed when both calmodulin proteins are bound.

"Calcium pumps need considerable energy to transport calcium out of the cell. It is therefore important that they are only activated when there is a need to remove calcium. With two calmodulin-binding domains in the calcium pump, the cell can adjust the transportation to be energy efficient, at the same time as being able to quickly reduce the number of if the concentration approaches a toxic level," Dr Poulsen concludes.

The researchers also used mathematical network modelling to further identify whether the calcium pump works differently depending on whether it is activated by zero, one or two calmodulin proteins. This revealed another characteristic of calcium pump regulation of calcium in the cell.

"We could show that the cell only responded to incoming calcium when concentrations above carefully defined threshold values were found. This may be important for the way cells define their status in the circadian rhythm or during cell division, for example," concludes Dr Tidow.

Explore further: Study finds new links between number of duplicated genes and adaptation

More information: DOI: 10.1038/nature11539

Related Stories

Like eavesdropping at a party

Jul 31, 2008

Cells rely on calcium as a universal means of communication. For example, a sudden rush of calcium can trigger nerve cells to convey thoughts in the brain or cause a heart cell to beat. A longstanding mystery has been how ...

Researchers uncover activation signal for Aurora-A oncogene

Sep 07, 2010

Aurora-A kinase (AurA) is an enzyme that is hyperactive in many cancers and drives tumor cell proliferation. Several AurA inhibitors are currently being tested in clinical trials to see if they slow tumor growth. Now, researchers ...

Channeling into cell control

Jan 20, 2012

A research team from the RIKEN Brain Science Institute in Wako, Japan, has visualized and accurately modeled the molecular changes that open and close the internal membrane channels for calcium ions within ...

Calcium is spark of life, kiss of death for nerve cells

Mar 01, 2007

Oregon Health & Science University research shows how calcium regulates the recharging of high-frequency auditory nerve cells after they've fired a burst of signals, and it may have implications for neurological disorders.

Squeeze play: Protein's grip like a baseball bunter's

Oct 10, 2006

Like all good baseball players, the protein calmodulin appreciates the importance of maintaining a good grip. A vital regulatory protein in all plants and animals, calmodulin is known to grab hold of hundreds of different ...

Recommended for you

Chrono, the last piece of the circadian clock puzzle?

12 hours ago

All organisms, from mammals to fungi, have daily cycles controlled by a tightly regulated internal clock, called the circadian clock. The whole-body circadian clock, influenced by the exposure to light, dictates the wake-sleep ...

Drought hormones measured

12 hours ago

Floods and droughts are increasingly in the news, and climate experts say their frequency will only go up in the future. As such, it is crucial for scientists to learn more about how these extreme events affect plants in ...

Research traces the genetic print of the Asturian people

19 hours ago

The DNA of the people of Asturias still maintains the genetic prints of remote ages. A research conducted at the University of Oviedo proves that the old frontiers marked by the pre-Roman Astur settlements have left their ...

User comments : 0

More news stories

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Wireless industry makes anti-theft commitment

A trade group for wireless providers said Tuesday that the biggest mobile device manufacturers and carriers will soon put anti-theft tools on the gadgets to try to deter rampant smartphone theft.