In order to interact with the environment, bacteria secrete a whole arsenal of proteins. Researchers have now found how one of the transportation systems used for this purpose – the type VI secretion system – works for the single-celled organism Agrobacterium tumefaciens. They have identified the relevant transport proteins and their energy suppliers.
Export mechanism: To get to the outside, Hcp has to get past two cell membranes. This is only possible if it forms a complex with the two membrane proteins TssM (grey) and TssL (white). The energy for the export is produced by the interaction of TssM with the energy storage molecule ATP. Figure: modified from the Journal of Biological Chemistry
With colleagues at the Academia Sinica in Taiwan, RUB biologist Prof. Dr. Franz Narberhaus describes the findings in the Journal of Biological Chemistry. “The proteins involved also occur in other secretion apparatuses” explains Narberhaus from the Department of Microbial Biology. “Therefore, the results contribute to the general understanding of the system.”
Protein arsenal for many purposes
Bacteria use secreted proteins to make nutrients available, to fend off competitors and to infect human, animal or plant host cells. “Agrobacterium tumefaciens is a fascinating bacterium. It can genetically modify plants and stimulate tumour formation”, says Narberhaus. Five bacterial secretion systems have been known for a long time. The type VI system was only discovered a few years ago. Among other things, it transports the protein Hcp through two membranes into the environment – for what purpose is, as yet, unclear. The question of how the export of Hcp is driven was also unanswered. This is precisely what the German-Taiwanese team has now revealed.
Membrane protein TssM: the driver of the protein export
Narberhaus and his colleagues have shown that two proteins in the cell membrane of the bacteria, called TssL and TssM, are responsible for the export of Hcp. The molecule ATP, a cellular energy store, serves as fuel for the transport process. The membrane protein TssM binds the energy supplier ATP, thereby changing its own structure and splitting the ATP. The energy thus released allows the associated membrane protein TssL to bind its cargo (Hcp) so that a tripartite complex of TssM, TssL and Hcp is formed. Hcp only passes from the bacterial cell into the environment when this complex forms.
Successful cooperation between Bochum und Taiwan
“Large membrane proteins such as TssM are difficult to study biochemically. Our colleagues in Taiwan have done a great job” Prof. Narberhaus explains. “It will now be particularly interesting to explore the biological significance of the system.” The analyses of ATP splitting, also called hydrolysis, were established in Prof. Narberhaus’s laboratory by the doctoral student Lay-Sun Ma during a research visit. “Because of the participation in the Collaborative Research Centre SFB 642 ‘GTP- and ATP-dependent membrane processes’, we are able to offer ideal conditions for working with ATP-dependent proteins” the RUB-biologist explains. This is the second time that the DAAD has funded the cooperation between the laboratories of Franz Narberhaus and Erh-Min Lai. The successful cooperation is also to continue in the future. “It is bound to last for many years”, the Bochum researcher is convinced. The next exchange of doctoral students is planned for autumn.
L.-S. Ma, F. Narberhaus, E.-M. Lai (2012): IcmF family protein TssM exhibits ATPase activity and energizes type VI secretion, Journal of Biological Chemistry, doi: 10.1074/jbc.M111.301630
Further informationProf. Dr. Franz Narberhaus, Department of Microbial Biology, Faculty of Biology and Biotechnology at the Ruhr-Universität, 44780 Bochum, Germany, Tel. +49/234/32-23100
Click for moreMicrobial biology at the RUB
Dr. Josef König | idw
Fingerprint' technique spots frog populations at risk from pollution
27.03.2017 | Lancaster University
Parallel computation provides deeper insight into brain function
27.03.2017 | Okinawa Institute of Science and Technology (OIST) Graduate University
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
27.03.2017 | Earth Sciences
27.03.2017 | Life Sciences
27.03.2017 | Life Sciences