How the light-harvesting complexes required for photosynthesis get to their site of action in the plant cell is reported by RUB biologists in the Journal of Biological Chemistry. The team led by Prof. Dr. Danja Schünemann (RUB working group on the molecular biology of plant organelles) has demonstrated for the first time that a membrane protein interacts with a single soluble protein to anchor the subunits of the light-harvesting complexes in the membrane. The researchers propose a new model that explains the integration into the membrane through the formation of a pore.
New transport model: Proteins of the light-harvesting complexes (green) have to be installed in special membranes inside the chloroplasts (thylakoid membranes). Soluble proteins (43, 54) transport them there. The membrane protein Alb3 forms a pore through interaction with one of the soluble proteins (43), through which the light-harvesting complex proteins are inserted into the membrane (Figure published in the Journal of Biological Chemistry) Figure: The American Society for Biochemistry and Molecular Biology
Photosynthesis occurs in special areas of the plant cells, the chloroplasts, whereby the energy-converting process takes place in specific protein complexes (photosystems). To capture the light energy and efficiently transmit it to the photosystems, light-harvesting complexes are required which work like antenna. “The proteins of the light-harvesting complexes are the most abundant membrane proteins on Earth” says Dr. Beatrix Dünschede of the RUB. “There is a special transport mechanism that conveys them into the chloroplasts and incorporates them into the photosynthetic membrane”. Exactly how the various transport proteins interact with each other had, up to now, been unclear.
Interaction between only two proteins
Several soluble proteins and the membrane protein Alb3 that channels the proteins of the light-harvesting complexes into the membrane are involved in the transport. Bochum’s biologists examined intact, isolated plant cells and found that, for this purpose, Alb3 interacts with only a single soluble transport protein (cpSRP43). They confirmed this result in a second experiment with artificial membrane systems. “In a further experiment, we identified the region in Alb3 to which the soluble protein cpSRP43 binds” explains the RUB biologist Dr. Thomas Bals. “It turned out that the binding site is partly within the membrane and thus cannot be freely accessible for cpSRP43.”
Through the pore into the membrane
Schünemann’s team explains the data with a new model. The soluble transport proteins bind the proteins of the light-harvesting complexes and transport them to the membrane. There, the soluble transport protein cpSRP43 interacts with the membrane protein Alb3, which then forms a pore. The proteins of the light-harvesting complexes get into the pore, and from there they are released laterally into the membrane. “There are proteins in other organisms which are very similar to Alb3 and apparently also form pores” says Dünschede. “This supports our model. We are now planning new experiments in order to recreate the entire transport path in an artificial system.”
B. Dünschede, T. Bals, S. Funke, D. Schünemann (2011) Interaction studies between the chloroplast signal recognition particle subunit cpSRP43 and the full-length translocase Alb3 reveal a membrane-embedded binding region in Alb3, Journal of Biological Chemistry, 286, 35187-35195, doi: 10.1074/jbc.M111.250746
Working group on the molecular biology of plant organelles, Department for Biology and Biotechnology at the Ruhr-Universität, 44780 BochumDr. Beatrix Dünschede, Tel. 0234/32-28467
Dr. Josef König | idw
Symbiotic bacteria: from hitchhiker to beetle bodyguard
28.04.2017 | Johannes Gutenberg-Universität Mainz
Nose2Brain – Better Therapy for Multiple Sclerosis
28.04.2017 | Fraunhofer-Institut für Grenzflächen- und Bioverfahrenstechnik IGB
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...
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...
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...
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...
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...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences