Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The role of the tunnel

31.01.2017

Freiburg researchers discover new molecular details about protein sorting in the cell

The targeted incorporation of proteins into the membrane is a vital process for cell maintenance; these membrane proteins ensure the proper functioning of the cell’s metabolism, communication with its environment, and energy supply.


The protein-sorting complex SRP scans the ribosome protein tunnel where proteins are being synthesized. When it recognizes a protein of the right kind, SRP positions its binding pocket at the end of the tunnel, where it forms a stable complex with the protein and transports it to the target site in the membrane. Graphic: AG Koch

Protein-sorting mechanisms ensure that membrane proteins are specifically recognized among thousands of different proteins – and are sent to the membrane, where they’re needed. A team headed by Kärt Denks, a doctoral candidate in Professor Hans-Georg Koch’s working group at the Institute of Biochemistry and Molecular Biology at the University of Freiburg, describes this molecular mechanism in detail in the journal Nature Microbiology, using the gut bacterium Escherichia coli.

The researchers showed that the signal recognition particle (SRP), present in all living organisms, identifies correct proteins already during their synthesis.

Proteins are synthesized on ribosomes, functional units within the cell, which release proteins via a tunnel to the inner part of the cell. They are then sorted according to a pattern: Proteins to be transported contain an amino acid sequence which serves as a recognition signal for cellular sorting complexes. SRP is one of these complexes.

It occurs in bacteria and in organisms with nucleated cells, and is responsible for the recognition of membrane proteins. From earlier investigations, the researchers knew that SRP recognizes membrane proteins even before they are fully synthesized. But there was debate over exactly when. At first it was assumed that the signal sequence had to have emerged completely from the ribosome protein tunnel for the membrane protein to be recognized. But subsequent work indicated that identification took place long before the signal sequence left the ribosome. The new Freiburg research confirms this.

The researchers used a technique which enabled them to examine the contacts between the ribosome and SRP right down to the level of individual amino acids – the very building-blocks of proteins. The team showed that SRP scans the ribosome protein tunnel to find potential substrate proteins. When it recognizes a protein of the right kind, it retracts to the end of the tunnel and positions its binding pocket in order to form a stable complex with the membrane protein.

Once it has done that, the SRP begins the process of moving the synthesizing ribosome to its target site at the membrane: where it binds to protein transport channels in order to anchor the protein into the membrane. If this early-recognition fails – if for instance the contact points between the SRP and the ribosomal tunnel have been genetically modified – membrane proteins pile up because they cannot be correctly positioned in the membrane. This leads to cell-division defects.

The research reveals a new complexity in the interaction between ribosomes and protein-sorting complexes: the ribosomal tunnel, long regarded as a passive tube, plays a key role in the coordination of processes which begin during the synthesis of proteins.

Hans-Georg Koch is the principle investigator of the German Research Foundation-sponsored research training group 2202, “Transport across and into membranes” and of the Faculty of Medicine’s doctoral training group “MOTI-VATE”. He is also vice-director of the Spemann Graduate School of Biology and Medicine (SGBM).

Original publication:
Kärt Denks, Nadine Sliwinski, Veronika Erichsen, Bogdana Borodkina, Andrea Origi, and Hans-Georg Koch (2017): The signal recognition particle contacts uL23 and scans substrate translation inside the ribosomal tunnel. In: Nature Microbiology, DOI: 10.1038/nmicrobiol.2016.265


Contact:
Professor Dr. Hans-Georg Koch
Institute of Biochemistry and Molecular Biology
University of Freiburg
Phone: 0761/203-5250
Email: hans-georg.koch@biochemie.uni-freiburg.de

Weitere Informationen:

http://www.pr.uni-freiburg.de/pm/2017/pm.2017-01-31.12-en

Rudolf-Werner Dreier | Albert-Ludwigs-Universität Freiburg im Breisgau

More articles from Life Sciences:

nachricht Full of hot air and proud of it
18.04.2018 | University of Pittsburgh

nachricht Keeping the excitement under control
18.04.2018 | Max-Delbrück-Centrum für Molekulare Medizin in der Helmholtz-Gemeinschaft

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

Im Focus: The Future of Ultrafast Solid-State Physics

In an article that appears in the journal “Review of Modern Physics”, researchers at the Laboratory for Attosecond Physics (LAP) assess the current state of the field of ultrafast physics and consider its implications for future technologies.

Physicists can now control light in both time and space with hitherto unimagined precision. This is particularly true for the ability to generate ultrashort...

Im Focus: Stronger evidence for a weaker Atlantic overturning

The Atlantic overturning – one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards – is weaker today than any time before in more than 1000 years. Sea surface temperature data analysis provides new evidence that this major ocean circulation has slowed down by roughly 15 percent since the middle of the 20th century, according to a study published in the highly renowned journal Nature by an international team of scientists. Human-made climate change is a prime suspect for these worrying observations.

“We detected a specific pattern of ocean cooling south of Greenland and unusual warming off the US coast – which is highly characteristic for a slowdown of the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

New capabilities at NSLS-II set to advance materials science

18.04.2018 | Materials Sciences

Strong carbon fiber artificial muscles can lift 12,600 times their own weight

18.04.2018 | Materials Sciences

Polymer-graphene nanocarpets to electrify smart fabrics

18.04.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>