The hidden machinery of a photosynthetic giant revealed

Although the structure of trimeric PSI from the thermophilic cyanobacterium Thermosynechococcus elongatus was solved 20 years ago, it was not yet possible to obtain the corresponding structure of monomeric PSI. Major bottleneck was the low natural abundance of this specific PSI form. Therefore, a new extraction method was developed by the researchers at RUB, which enabled selective isolation of PSI monomers with high yield. The isolated protein complex was characterized in detail at RUB by mass-spectrometry, spectroscopy and biochemical methods, whereas the research team at Osaka University was able to solve its structure by cryo-electron microscopy. Teamwork between chlorophylls and lipids might enable uphill energy transfer

The atomic structure of monomeric PSI provides novel insights into the energy transfer inside the protein complex as well as on the localization of so-called red chlorophylls -- specially arranged chlorophylls, closely interacting with each other and thus enabling the absorption of low-energy far red light, which normally cannot be used for photosynthesis. Interestingly, the structure revealed that the red chlorophylls seem to interact with lipids of the surrounding membrane. This structural arrangement might indicate that additional thermal energy is used to make far red light accessible for photosynthesis. Long-run cooperation bears further fruits