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 Decoding the genome's cryptic language
27.02.2017 | University of California - San Diego

nachricht New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New pop-up strategy inspired by cuts, not folds

27.02.2017 | Materials Sciences

Sandia uses confined nanoparticles to improve hydrogen storage materials performance

27.02.2017 | Interdisciplinary Research

Decoding the genome's cryptic language

27.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>