Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How bacteria integrate autotransporters into their outer membrane

23.09.2013
The bacterial outer envelope is densely packed with proteins that form small pores and facilitate the passage of nutrients, toxins and signaling molecules.

Professors Timm Maier and Sebastian Hiller from the Biozentrum of the University of Basel now demonstrate how these transporter proteins are integrated into the outer membrane.


Proposed mechanism how bacteria integrate autotransporter into their outer membrane. Left: protein structure of TamA, right: TamA with autotransporters (orange).

Using x-ray structural analysis they reveal the structure-function relationship of the protein TamA, which plays an important role in the assembly of transport proteins in the bacterial outer membrane. Their findings have been published recently in the renowned scientific journal «Nature Structural and Molecular Biology».

Shuttling proteins from inside the cell to the outside environment is a complex task for Gram-negative bacteria, which are not only surrounded by an inner membrane, but also by an outer membrane barrier for protection against adverse environmental conditions.

The bacteria however, can overcome this additional barrier by inserting special transport proteins into the protective outer membrane. In a joint project, Maier and Hiller, both Professors of Structural Biology at the Biozentrum of the University of Basel, provide mechanistic insights into this key process.

The structure of the assembly protein TamA explains its function

An important option for channeling protein domains across the outer membrane are so-called autotransporters. These membrane proteins form a barrel-like structure with a central pore, but they cannot autonomously transport their “passenger domain” across the outer membrane.

Specific assembly proteins are required for the folding and integration of autotransporters into the outer membrane. Employing x-ray crystallography, the authors of the study decoded the atomic structure of the autotransporter assembly protein TamA of the intestinal bacterium Escherichia Coli.

“The protein TamA”, explains Fabian Gruss, first author and recipient of a Werner-Siemens PhD fellowship, “also forms a barrel with a pore. The pore is closed to the outside by a lid but a particular kink in the barrel wall provides a gate for autotransporter substrates.” When an unfolded autotransporter is delivered, TamA hooks onto one end of the substrate polypeptide chain and integrates it step by step via the gate into its own barrel structure.

The TamA barrel is thus expanded; the pore widens and opens such that passenger substrates traverse to the exterior. The assembly process ends when TamA releases the autotransporter into the surrounding membrane. “The autotransporter insertion mechanism was previously completely enigmatic – for the first time, knowing the structure of TamA, we can now picture how assembly and translocation could function.”

Assembly process important for infections

Many pathogens, such as the diarrhea causing Yersinia, Salmonella or the Cholera pathogen, belong to the group of Gram-negative bacteria. With the help of the autotransporter, they release toxins or adhesive proteins to infect their host cells. In their study, Maier and Hiller provide completely new findings about membrane insertion of autotransporters as well as the translocation of their cargo.

Original Citation
Fabian Gruss, Franziska Zähringer, Roman P. Jakob, Björn M. Burmann, Sebastian Hiller, Timm Maier.
The structural basis of autotransporter translocation by TamA.
Nature Structural and Molecular Biology, Published online 23 September 2013
Further Information
Prof. Dr. Timm Maier, Biozentrum of the University of Basel, Tel.: +41 61 267 21 76,
E-Mail: timm.maier@unibas.ch
Prof. Dr. Sebastian Hiller, Biozentrum of the University of Basel, Tel.: +41 61 267 20 82, E-Mail: sebastian.hiller@unibas.ch

Weitere Informationen:

http://www.nature.com/nsmb/journal/vaop/ncurrent/abs/nsmb.2689.html - Abstract

Christoph Dieffenbacher | Universität Basel
Further information:
http://www.unibas.ch

More articles from Life Sciences:

nachricht At last, butterflies get a bigger, better evolutionary tree
16.02.2018 | Florida Museum of Natural History

nachricht New treatment strategies for chronic kidney disease from the animal kingdom
16.02.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>