Detailed structure of the light-harvesting antenna of cyanobacteria.
Author: University of South Bohemia in České Budějovice
1/9/2022 6:30 p.m
SOUTH BOHEMIA – The collaboration of scientists from Michigan State University, the University of California Berkeley, Lawrence Berkeley National Laboratory, the University of South Bohemia in České Budějovice and the Biological Center of the Academy of Sciences of the Czech Republic has led to an important discovery in the field of photosynthesis. The study, in which Tomáš Polívka and David Bína from the University of South Bohemia in České Budějovice and the Biological Center of the Academy of Sciences of the Czech Republic also participated, was published on August 31 in the most prestigious scientific journal, Nature.
Photosynthesis is a key process for sustaining life on the planet, as it is the only one able to process solar energy and convert it into other forms of energy that living organisms, including humans, can use. As all food is of photosynthetic origin, whether as a primary product (fruit, vegetables, grain…) or as a secondary product (meat, milk…), a detailed understanding of photosynthetic processes is essential not only for basic research, but also for mastering social challenges such as ensuring enough food for the ever-increasing population on the planet.
Photosynthesis is today mainly associated with green plants, but even simpler organisms, such as cyanobacteria, can use sunlight through photosynthesis. And it is these simpler organisms that the published study targets. All photosynthetic organisms have special structures composed of proteins, the sole task of which is to capture sunlight and transfer the energy obtained to other proteins, which transform it into chemical energy. These formations, which are called light-harvesting antennae, are very specific to cyanobacteria, and their detailed structure and mechanism of energy transfer have not yet been known.
A nine-member team composed of experts in electron microscopy, structural biology, molecular biology and biophysics has now succeeded in describing and visualizing these cyanobacterial antennae in detail. In addition, detailed knowledge of the structure made it possible to find out how the trapped energy is transferred throughout the system. This analysis was carried out by South Bohemian scientists. “We were lucky to have created a team of experts from different fields who complemented each other perfectly. The whole group had the right chemistry,” says Cheryl Kerfeld, professor of structural bioengineering at Michigan State University, who led the entire project. “The result is eleven pages of discoveries and surprises,” adds Maria Agustina Domínguez-Martín, first author of the publication. The space that the journal Nature gave to this study is extraordinary, as most publications in this prestigious journal are roughly half the size. This only underlines the importance of the work of an international team of scientists.
In addition to understanding the structure and function of the light-harvesting antennae of cyanobacteria, the study contains another important discovery. All photosynthetic organisms face the problem of how to protect their photosynthetic apparatus when there is too much light. In cyanobacteria, it has been known for a long time that a small protein called OCP (Orange Carotenoid Protein) is responsible for the regulation of energy flow, but until now it was not at all clear how this protein works. Using electron microscopy, an international team of scientists managed to reveal the places where this small protein binds to the antenna. This was the first crucial step in understanding the mechanism of how this protein can affect the flow of energy in a much larger light-harvesting antenna. Subsequent modeling of energy transfer, which was the result of the work of South Bohemian scientists, reliably explained the mechanism of action of this protein. The whole system is optimized so that the OCP protein takes excess energy from the antenna and safely converts it into heat. “I really appreciate the opportunity to work in this great team,” says Tomáš Polívka, professor of biophysics at the Faculty of Science of the University of South Bohemia, who has been working with Cheryl Kerfeld for almost twenty years. “Seeing the structure of the entire system for the first time was an incredible experience. It was immediately clear that a fundamental breakthrough that will allow us to understand in detail how the system works,” he adds.
Understanding the structure and mechanism of capturing and regulating light energy in cyanobacteria is a breakthrough discovery, especially because it is the first time in the history of photosynthetic research that it is possible to see how a photosynthetic organism limits its performance in the event of an excessive amount of light. The study is a starting point for further research, including possible applications in the field of artificial photosynthesis, biotechnologies using cyanobacteria, for example for obtaining specific substances or even limiting the unwanted occurrence of cyanobacteria on water surfaces.
Author: Štěpán Kuděj, press officer, University of South Bohemia in České Budějovice
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