Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Proteins hoist the anchor

06.08.2013
PNAS: How switch proteins are extracted from the membrane

Researchers from the Ruhr-Universität Bochum (RUB) and from the MPI Dortmund have for the first time successfully reproduced the recycling process of proteins regulating cellular transport in a biophysical experiment. In doing so, they traced in detail the way the central switch protein Rab is being extracted from the lipid membrane.


The Rab protein (grey and magenta) with bound GDP (multi-coloured) sits on a membrane surface. As the infrared ray is reflected from the surface, the processes that take place on the membrane can be studied. The GDI, represented by the hand, seizes the Rab protein and extracts it from the membrane. The timeline of the infrared spectra (top centre) is resolved in the spectrometer (top right).

Credit: Konstantin Gavriljuk, RUB

The team of PD Dr Carsten Kötting, Prof Dr Klaus Gerwert (Department of Biophysics, RUB) and Prof Dr Roger S. Goody (Max Planck Institute for Molecular Physiology, Dortmund) has published the spectroscopic and dynamic data in the PNAS journal's Online Early Edition. "Until now, this protein's interactions have only ever been studied in a solution – i.e. without a lipid membrane. The step into the protein's natural environment opens up entirely new possibilities," says Carsten Kötting. This is because many disease-relevant protein interactions within a cell take place on a membrane.

From solution to membrane

Unlike Ras proteins that regulate cell growth, Rab GTPases control the traffic between different cell sections. Just like Ras proteins, Rab GTPases (also called Rab proteins) act as switches. Turned "on", the high-energy GTP molecule is bound; turned "off", the lower-energy GDP molecule is bound. The switch protein Rab does not simply swim through the cell with the trafficked load it is carrying; rather, it is fixed within the membrane by means of lipid anchors. After the trafficking stage has been successfully completed, Rab is extracted from the membrane and recycled. This process has never yet been simulated in a biophysical experiment. The Bochum-Dortmund team has succeeded in manufacturing the Rab protein with the membrane anchor in its active form in large quantities, to bind it to an artificial lipid membrane and to investigate the process of extracting the switch protein from the membrane in a spectrometer.
Seize and pull hard

For this purpose, biophysicists used the method of ATR infrared spectroscopy, which enabled them to visualise processes on surfaces such as lipid membranes. They paid particular attention to the GDI protein that binds the Rab protein and its lipid anchor. The question was whether Rab dissociates spontaneously from the membrane and is seized by GDI or whether GDI plays an active part in the Rab recycling process. With ATR spectroscopy, the team was for the first time able to differentiate between these two processes and demonstrate the GDI protein's active role. "We observed that GDI approaches the membrane and seizes the Rab protein then and there," explains Konstantin Gavriljuk. "Thus, Rab is extracted from the membrane by GDI much more quickly than it would have otherwise dissociated."
Legionella affect cellular trafficking processes

Rab GTPases and their interaction partners have an impact on certain diseases, for example some forms of mental disabilities and legionnaire's disease. The agents causing legionnaire's disease, namely legionella, attack Rab proteins and modify them chemically, thus affecting cellular trafficking processes; they are thus able to reproduce in human cells. The experiments have shown that the chemical modification caused by legionella inhibits the process of Rab extraction from the membrane by GDI. "We have now gained a better understanding of where legionella attack cells and of the consequences thereof," says Carsten Kötting.

Project funding

The project funds are supplied by SFB 642 "GTP and ATP-dependent Membrane Processes", whose spokesperson is Prof Gerwert.

Bibliographic record

K. Gavriljuk, A. Itzen, R.S. Goody, K. Gerwert, C. Kötting (2013): Membrane extraction of Rab proteins by GDP dissociation inhibitor characterized using attenuated total reflection infrared spectroscopy, PNAS, doi:10.1073/pnas.1307655110
Further information

Prof Dr Klaus Gerwert, Department of Biophysics, Faculty of Biology and Biotechnology at the Ruhr-Universität, 44780 Bochum, Germany, tel. +49/234/32-24461, e-mail: klaus.gerwert@bph.rub.de

PD Dr Carsten Kötting, Department of Biophysics, Faculty of Biology and Biotechnology at the Ruhr-Universität, 44780 Bochum, Germany, tel. +49/234/32-24461, e-mail: Koetting@bph.rub.de

A click away

Previous information re.: Rab
http://aktuell.ruhr-uni-bochum.de/pm2012/pm00416.html.en
Editor: Dr. Julia Weiler

Dr. Carsten Kötting | EurekAlert!
Further information:
http://www.ruhr-uni-bochum.de

More articles from Life Sciences:

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

nachricht Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.

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 lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>