3D structure of an artificial photosynthetic antenna

Humans possess remarkable capabilities, yet plants hold a unique superpower: they convert sunlight into energy through photosynthesis. Recent research indicates that scientists are narrowing this gap significantly.

At Osaka Metropolitan University, researchers have uncovered the 3D structure of an artificial photosynthetic antenna protein complex known as light-harvesting complex II (LHCII). Their findings reveal that this artificial version closely resembles its natural counterpart. This breakthrough is pivotal for enhancing our understanding of how plants efficiently capture and utilize solar energy, setting the stage for groundbreaking advancements in artificial photosynthesis.

The study, led by Associate Professor Ritsuko Fujii and then graduate student Soichiro Seki from the Graduate School of Science and Research Center for Artificial Photosynthesis, was published in PNAS Nexus.

Photosynthesis transforms sunlight into usable energy through an intricate process that involves a vast array of molecules and proteins. At the heart of this is LHCII, the predominant pigment-protein complex found in the chloroplasts of plants and green algae, which plays a vital role in capturing sunlight and efficiently funneling energy to power photosynthesis.

Composed of numerous proteins and pigment molecules, the functionality of this photosynthetic antenna is complex and the task of mimicking it is daunting.

While many efforts have been made to replicate LHCII, the pressing question remains: how accurately do these imitations reflect nature’s own creation?

“Traditional methods struggle to elucidate the precise structure of in vitro reconstituted LHCII,” emphasized Dr. Seki.

In vitro reconstitution is a lab technique that empowers scientists to recreate LHCII outside of plants. By synthesizing the protein component of LHCII in E. coli and integrating it with natural pigments and lipids, researchers are paving the way for innovative discoveries.

The research team embraced this cutting-edge approach, employing cryo-electron microscopy to unveil the 3D structure of the reconstituted LHCII. This Nobel Prize-winning technique from 2017 allows researchers to capture stunning images of samples frozen at ultra-low temperatures, enabling them to discover intricate details of how pigments and proteins are precisely organized within this complex assembly.

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

These findings confirm the efficacy of the in vitro reconstitution technique, paving the way for a deeper understanding of LHCII’s intricate mechanisms and its pivotal role in photosynthesis. This research lays a solid foundation for future innovations in artificial photosynthesis and advancements in 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,” Professor Fujii said. “We hope this will facilitate further studies on the molecular mechanisms by which plants utilize sunlight for chemical reactions.”

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