Researchers have successfully mapped the 3D structure of a synthetic light-harvesting complex II (LHCII), which is essential for the photosynthesis process. By employing cryo-electron microscopy, they discovered that this artificial LHCII closely resembles its natural equivalent, marking significant progress in the fields of solar energy collection and artificial photosynthesis technologies.
Humans are capable of many things, but plants possess a unique ability: they convert sunlight into energy, a process known as photosynthesis. Recent studies indicate that scientists are making strides to replicate this ability.
Researchers from Osaka Metropolitan University have revealed the 3D structure of an artificial photosynthetic antenna protein complex, referred to as light-harvesting complex II (LHCII), demonstrating that this synthetic version closely resembles the natural one. This breakthrough enhances our understanding of how plants capture and utilize solar energy, paving the way for advancements in artificial photosynthesis.
Led by Associate Professor Ritsuko Fujii and then graduate student Soichiro Seki from the Graduate School of Science and Research Center for Artificial Photosynthesis, their findings were published in PNAS Nexus.
Photosynthesis is an intricate process that transforms sunlight into usable energy, involving numerous molecules and proteins. LHCII is the most prevalent pigment-protein complex found in plant chloroplasts and green algae, playing a crucial role in capturing sunlight and directing energy efficiently to fuel photosynthesis. LHCII’s structure includes various proteins and pigment molecules, making it complex to mimic its function accurately.
Several efforts have been made to replicate LHCII, with the key question being: do these synthetic versions resemble the natural one?
“Conventional methods have not succeeded in revealing the precise structure of in vitro reconstituted LHCII,” commented Dr. Seki.
In vitro reconstitution is a laboratory method that allows scientists to assemble LHCII outside of plants by synthesizing its protein in E. coli and mixing it with natural pigments and lipids.
Consequently, the research team adopted a novel approach, using cryo-electron microscopy to examine the 3D arrangement of the reconstituted LHCII. This award-winning technique, which won the Nobel Prize in Chemistry in 2017, captures images of samples frozen at extremely low temperatures, enabling a highly detailed view of how pigments and proteins are organized within the complex.
“Our findings indicated that the synthetic LHCII was almost identical to the natural variant, with only a few slight differences,” Dr. Seki noted.
These results confirm the potential of the in vitro reconstitution method and create new avenues for further exploration of LHCII’s functions and its role in photosynthesis, laying a path for future innovations in artificial photosynthesis and advancements in plant production technology.
“Our research not only establishes a structural basis for reconstituted LHCII but also assesses its functions through its structure,” Professor Fujii explained. “We anticipate that this will promote further investigations into the molecular mechanisms plants use to harness sunlight for various chemical reactions.”
