Deep within chloroplasts, in specific protein complexes called photosystems, light-harvesting complexes work like antennas, capturing light energy and efficiently transmitting it to the photosystems. But exactly how the transport proteins interact with one another has been a mystery to scientists, until now. For the first time, biologists have shown how a plant membrane protein interacts with a single soluble protein to effectively anchor the subunits of the light-harvesting complexes within that membrane. Their new model explains the integration into the membrane through the formation of a pore. Biologists from Ruhr University Bochum examined intact isolated plant cells and found that, for this purpose, membrane protein Alb3 interacts with only a single soluble transport protein, cpSRP43. They confirmed their observations in a second experiment with artificial membrane systems. The binding site was found partly within the membrane and thus is not freely accessible for cpSRP43, the researchers concluded. They proposed a model to explain the data: The soluble transport proteins bind the proteins of the light-harvesting complexes and transport them to the membrane. There, the cpSRP43 interacts with the Alb3, forming a pore. The proteins of the light-harvesting complexes get into the pore and are released laterally into the membrane. The biologists are looking at ways to recreate the entire transport path in an artificial system, which could lead to artificial photosynthesis for energy production. The work was published in the Journal of Biological Chemistry (doi: 10.1074/jbc.M111.250746).