In plant cells, complex I is used in two places: one is in mitochondria, the cell's power plants, the other is in chloroplasts, where photosynthesis occurs. In both instances, it forms part of an electron transport chain, which can be thought of as biology's electrical circuit. These are used to drive the cells' molecular machines responsible for energy production and storage.
The researchers showed that the molecular structure of photosynthetic complex I differs considerably from its respiratory relative. In particular, the part responsible for electron transport has a different structure, since it is optimized for cyclic electron transport in photosynthesis. In the next step, the team analyzed the structural elements responsible for the efficient interaction of complex I and the protein ferredoxin. They found that complex I has a particularly flexible part in its structure, which captures the protein ferredoxin like a fishing rod. This allows ferredoxin to reach the optimal binding position for electron transfer.
For more details, read the press release from Ruhr-Universität Bochum.