HKUST Researchers Uncover Assembly Mechanism of Carbon-Fixing Carboxysomes

Researchers at Hong Kong University of Science and Technology (HKUST) uncover the assembly mechanism of carboxysomes, tiny carbon-fixing structures in bacteria and algae. The team uses cryo-electron microscopy to determine the structure and assembly pattern of the protein shell, paving the way for improving photosynthesis efficiency.

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Bijay Laxmi
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HKUST Researchers Uncover Assembly Mechanism of Carbon-Fixing Carboxysomes

HKUST Researchers Uncover Assembly Mechanism of Carbon-Fixing Carboxysomes

A research team led by Prof. ZENG Qinglu from the Hong Kong University of Science and Technology (HKUST) has made a significant breakthrough in understanding the assembly mechanism of carboxysomes, tiny carbon-fixing structures found in certain bacteria and algae. The discovery, published in the scientific journal Nature Plants, could pave the way for improving photosynthesis efficiency, potentially increasing the global food supply and mitigating global warming.

Why this matters: This breakthrough has significant implications for addressing global food security and climate change, two of the most pressing issues of our time. By improving photosynthesis efficiency, we can increase crop yields and reduce atmospheric CO2 levels, ultimately contributing to a more sustainable future.

Carboxysomes are tiny compartments that encase specific enzymes in a shell made of proteins, performing carbon fixation, which is the process of converting carbon dioxide from the atmosphere into organic compounds used by cells for growth and energy. The HKUST-led team, in collaboration with Prof. ZHOU Cong-Zhao from the University of Science & Technology of China, utilized single-particle cryo-electron microscopy to determine the structure of α-carboxysome and characterize the assembly pattern of the protein shell, which resembles a 20-sided shape with specific proteins arranged on its surface.

The team discovered that the minimal α-carboxysome has a diameter of 86 nm and consists of RuBisCO enzymes arranged in three concentric layers, held together by a protein called CsoS2. Prof. Zeng explained, "Our study unveils the mystery of α-carboxysome assembly from Prochlorococcus, thus providing novel insights into global carbon cycling." The findings suggest that carboxysomes are assembled from the outside in, with the inside surface of the shell strengthened by certain parts of the CsoS2 protein, while other parts attract the RuBisCO enzymes and organize them into layers.

The discovery could lead to the introduction of carboxysomes into plant chloroplasts, improving photosynthetic efficiency and crop yield. Understanding the CO2 fixation mechanism of marine cyanobacteria could also enable the improvement of their CO2 fixation rate, potentially removing more CO2 from the atmosphere and slowing down global warming. "Our understanding of the CO2 fixation mechanism of marine cyanobacteria will enable us to improve their CO2 fixation rate so that more CO2 can be removed from the atmosphere," Prof. Zeng added.

The team plans to introduce Prochlorococcus α-carboxysome into plant chloroplasts and investigate whether the minimal α-carboxysome can improve photosynthetic efficiency in plants. They also aim to modify the carboxysome genes and create genetically modified super cyanobacteria that can fix carbon dioxide at very high rates, potentially slowing down global warming.

The groundbreaking study by the HKUST-led research team provides valuable insights into the assembly mechanism of carboxysomes and their potential applications in improving photosynthesis efficiency and mitigating global warming. As the world faces the challenges of food security and climate change, this discovery opens up new possibilities for enhancing crop yields and reducing atmospheric CO2 levels.