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
New eDNA technology used to quickly assess coral reefs
18.04.2019 | University of Hawaii at Manoa
New automated biological-sample analysis systems to accelerate disease detection
18.04.2019 | Polytechnique Montréal
A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter
A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.
Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...
The technology could revolutionize how information travels through data centers and artificial intelligence networks
Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...
Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.
Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...
Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna
A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...
17.04.2019 | Event News
15.04.2019 | Event News
09.04.2019 | Event News
18.04.2019 | Life Sciences
18.04.2019 | Physics and Astronomy
18.04.2019 | Life Sciences