Quality control in synthetic photosynthesis validates natural light-harvesting mimicry

Quality control in synthetic photosynthesis validates natural light-harvesting mimicry

by Riko Seibo

Osaka, Japan (SPX) Oct 29, 2024

Humans can do many impressive things, but plants possess a unique ability: they directly convert sunlight into energy through photosynthesis. Now, recent research suggests scientists are narrowing the gap in replicating this process artificially.

Researchers from Osaka Metropolitan University have successfully mapped the 3D structure of an artificial photosynthetic antenna protein complex, called light-harvesting complex II (LHCII), and demonstrated that this synthetic LHCII closely mimics its natural equivalent. This breakthrough significantly enhances understanding of how plants capture and direct solar energy, marking an essential step toward advancements in artificial photosynthesis.

Led by Associate Professor Ritsuko Fujii and former graduate student Soichiro Seki from the Graduate School of Science and Research Center for Artificial Photosynthesis, the study has been published in PNAS Nexus.

Photosynthesis, the process by which sunlight is transformed into usable energy, involves numerous intricate interactions among various molecules and proteins. LHCII is among the most crucial components – a pigment-protein complex found in plant and algae chloroplasts, which is instrumental in capturing sunlight and channeling energy for photosynthesis. Comprising an intricate array of proteins and pigments, LHCII is a challenging structure to reproduce outside natural systems.

Several previous efforts aimed at replicating LHCII have raised the question: Do these artificial constructs come close to nature’s original design?

“Traditional methods fall short of determining the exact structure of in vitro reconstituted LHCII,” commented Dr. Seki.

In vitro reconstitution, a laboratory technique, allows scientists to recreate LHCII outside plants by synthesizing its protein portion in *E. coli* and pairing it with natural pigments and lipids.

Turning to advanced cryo-electron microscopy, the research team analyzed the 3D structure of the artificially reconstituted LHCII. This technique, which was awarded the Nobel Prize in Chemistry in 2017, involves freezing samples at extremely low temperatures to capture highly detailed images. Through this method, the team gained an in-depth view of how pigments and proteins align within the synthetic complex.

“Our results showed that the lab-created LHCII was nearly identical to the natural version, with only a few minor differences,” stated Dr. Seki.

These findings confirm the efficacy of the in vitro reconstitution technique and open doors to further studies on LHCII’s functional role in photosynthesis. The research sets the stage for innovations in artificial photosynthesis and plant production technologies.

“Our result provides not only a structural foundation for reconstituted LHCII, but also evaluates the functions based on the structure of the reconstituted LHCII,” added Professor Fujii. “We hope this will facilitate further studies on the molecular mechanisms by which plants utilize sunlight for chemical reactions.”

Research Report:Structure-based validation of recombinant light-harvesting complex II