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Photosynthesis: oil in the gears

Researchers from the Biam have discovered one of the "lubricants" of the complex gears involved in photosynthesis.

Published on 10 November 2017

If numerous researchers are working on photosynthesis (especially at the DRF), it is because this key mechanism of living things still holds many mysteries. Photosynthesis captures CO2 and produces oxygen and sugars. This chemistry is made possible thanks to the energetic contribution of light and its regulation. The mechanisms of this regulation are even more precise than a Swiss watch. In particular, solar energy must be distributed between one photosystem and another in a well-oiled system. "Two photosystems capture light energy", explains Jean Alric, a researcher at the Biam. "Both of them are connected in series. They need to receive light energy in the correct proportions." 

A team from the Biam, in collaboration with a group from the Institute of Physicochemical Biology, has demonstrated that an enzyme called cytochrome b6f is one of the conductors of this regulation. This cytochrome induces a cascade of chemical events. "Through a protein-protein interaction, cytochrome b induces the autophosphorylation of a protein named Stt7, which in turn phosphorylates the proteins that capture light", explains the biologist. These phosphorylation changes, which are reflected in the contribution of a phosphate group, cause a reorganization in the structure of the photosynthetic membranes. "In the dephosphorylated state, these membranes are stacked on top of each other", says Jean Alric. "Phosphorylation by Stt7 destabilizes this stacking, causing a repulsion between the membranes and the migration of proteins that capture light. This change in architecture readjusts the distribution of photons between the two photosystems."

The fluidity of the photosynthetic membrane and its associated regulations thus allow the operation of a "well-oiled mechanism" that is resistant to heating and, as a consequence, and energy-efficient.

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