Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers Observe Spontaneous 'Ratcheting' Of Single Ribosome Molecules

06.06.2008
Researchers report this week that they are the first to observe the dynamic, ratchet-like movements of single ribosomal molecules in the act of building proteins from genetic blueprints.

Their study, published in the journal Molecular Cell, reveals a key mechanism in the interplay of molecules that allows cells to build the proteins needed to sustain life.

Cells use a variety of tools to build proteins, beginning with messenger RNA, a ribbon-like molecule that codes for the sequence of amino acids in the protein. Another molecule, transfer RNA (tRNA) is uniquely qualified to read this code, but can do so only within the confines of the ribosome. Transfer RNAs bring individual amino acids into the ribosome where they are assembled into proteins. Various other proteins also participate in the process.

When protein translation occurs, single tRNAs enter specific sites in the ribosome, read the code and deliver their amino acids – one by one – to a growing protein chain. The ribsome transits along the messenger RNA as the protein is built, releasing the “deacylated” tRNA through an exit site.

... more about:
»EF-G »RNA »acid »amino »amino acids »ribosomal »spontaneously »tRNA

A ribosome is made up of two subunits composed of ribonucleic acids (RNAs) and about 50 individual proteins.

The ribosome was once considered a static “workbench” for the assembly of new proteins. A recent study by researchers at the Wadsworth Center in Albany, N.Y., using cryo-electron microscopy, showed the ribosomal subunits in two distinct positions relative to one another, however. They proposed that the motion of the subunits depended on a protein catalyst, elongation factor G (EF-G).

In the new study, a team led by University of Illinois physics professor Taekjip Ha used fluorescence resonance energy transfer (FRET) to observe in real time the movement of the ribosomal subunits that is essential for protein synthesis. The team collaborated with Harry Noller, of the University of California at Santa Cruz, who provided expertise on the ribosome.

FRET makes use of fluorescent molecules whose signals vary in intensity depending on their proximity to one another. By labeling each of the two subunits of a single ribosomal molecule with these fluorescent markers, the researchers were able to watch the subunits move in relation to one another.

When Ha and postdoctoral fellow Peter Cornish observed the signal from the labeled ribosomes, they saw a spontaneous back-and-forth rotation between the subunits – even in the absence of the elongation factor, EF-G.

“Other researchers proposed that this rotation is induced by EF-G – that you have to have EF-G to cause this rotation,” Ha said. “But we showed that no, that’s not the case. Actually the ribosome can rock back and forth spontaneously, and can do it quite rapidly.”

The researchers were able to view this motion even in the absence of tRNA. The ribosomal subunits were spontaneously switching back and forth between the classical (that is, non-rotated) state and a hybrid (rotated) state.

When they added a single tRNA with an amino acid permanently attached to it, the ribosome became “essentially stuck in the classical, non-rotated state,” Cornish said. “And as soon as we removed that, it started to move spontaneously.”

To better understand the role of EF-G, the researchers added a modified EF-G molecule that could not deliver its normal energy payload to the ribosome. The modified EF-G bound to the ribosome only in the rotated, hybrid state.
These findings led the researchers to propose that EF-G has a critical role in the process of protein translation: It stabilizes the rotated position of the ribosomal subunits relative to one another.

This allows the tRNA molecules to add amino acids to the growing protein and to exit, making room for the next tRNA specified in the messenger RNA code.

The researchers believe that EF-G acts as a linchpin, temporarily holding the ribosome in its rotated position until the deacylated tRNAs reposition themselves in the molecule as they move toward the exit. Once the tRNAs have accomplished this, the EF-G goes away, the ribosome ratchets back into its non-rotated position and the process begins again.

The researchers propose that this ratcheting motion allows the ribosome to advance along the messenger RNA as protein translation progresses. Without EF-G, the ribosomal subunits move in relation to one another, but are unable to progress along the messenger RNA as a protein is built.

“Many people would argue that the ribosome is one of the most important machines in our cells,” Ha said. “What’s really amazing is that it is such a massive complex that is still able to move spontaneously, to rock back and forth at a fairly rapid rate. And that movement is not just some random movement, but it’s the most important movement of the ribosome for its locomotion.”

Future studies will use FRET by labeling both the ribosomal subunits and the messenger RNA to see if the movement of the subunits and the ribosome’s transit along the messenger RNA are synchronized, Ha said.

The study was supported in part by the National Science Foundation and the National Institute of General Medical Sciences at the National Institutes of Health. Ha is an investigator with the Howard Hughes Medical Institute.

Diana Yates | University of Illinois
Further information:
http://www.uiuc.edu

Further reports about: EF-G RNA acid amino amino acids ribosomal spontaneously tRNA

More articles from Life Sciences:

nachricht New technique unveils 'matrix' inside tissues and tumors
29.06.2017 | University of Copenhagen The Faculty of Health and Medical Sciences

nachricht Designed proteins to treat muscular dystrophy
29.06.2017 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making Waves

Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.

Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Nanostructures taste the rainbow

29.06.2017 | Physics and Astronomy

New technique unveils 'matrix' inside tissues and tumors

29.06.2017 | Life Sciences

Cystic fibrosis alters the structure of mucus in airways

29.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>