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 identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory

nachricht Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>