Orange is the new red: MSU researchers discover mechanism to protect cells from solar damage

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Emily Pawlowski, Cheryl Kerfeld and Ryan Leverenze in Kerfeld's lab. (view larger image)

Overexposure to sunlight, which is damaging to natural photosynthetic systems of green plants and cyanobacteria, is also expected to be damaging to artificial photosynthetic systems.

Nature has solved the problem through a photoprotection mechanism called “nonphotochemical-quenching.” This allows solar energy to be safely dissipated as heat from one molecular system to another.

With an eye on learning from nature’s success, a team led by Cheryl Kerfeld, the Hannah Distinguished Professor of Structural Bioengineering in the Michigan State University-DOE Plant Research Lab who is also an affiliate of Berkeley Lab’s Physical Biosciences Division, has discovered a surprising key event in this energy-quenching process.

In a recent paper published in Science, the team discovered that in cyanobacteria the energy-quenching mechanism is triggered by an unprecedented, large-scale (relatively speaking) shift of a single carotenoid pigment within a protein.

As a result of this shift, the carotenoid changes its shape slightly and interacts with a different set of amino acid neighbors causing the protein to change from an orange light-sensing state to a red photoprotective state.

“Prior to our work, the assumption was that carotenoids are static, held in place by the protein scaffold,” Kerfeld said. “Having shown that the translocation of carotenoid within the protein is a functional trigger for photoprotection, scientists will need to revisit other carotenoid-binding protein complexes to see if translocation could play a role in those systems as well. Understanding the dynamic function of carotenoids should be useful for the design of future artificial photosynthetic systems.”

For the full story, please visit MSU Today.

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