Cytochrome structure unravels photosynthesis

A complete molecular-scale picture of how plants convert sunlight to chemical energy has been obtained at Purdue University in the US, offering potential new insights into animal metabolism as well.

Using advanced imaging techniques, a team of biologists has determined the structure of the cytochrome, a protein complex that governs photosynthesis in a blue-green bacterium. While their work does not immediately suggest any industrial applications, it does reveal a wealth of information not only about a chemical process crucial to all life on the planet, but also about how cells handle and distribute energy. According to team member William Cramer, the study is a great leap forward in our understanding of photosynthesis.

"Where we once could see merely the tip of the iceberg, we can now perceive the entire mechanism of photosynthesis," said Cramer, the Henry Koffler Distinguished Professor of Biological Sciences in Purdue's School of Science. "Before we found a way to crystallise the cytochrome, we had a general picture of the photosynthetic process, but possessed only a fraction of a percent of the information we now have. Now that we can examine these proteins closely with X-ray crystallography, it could lead to knowledge about how all cells exchange energy with their environment."

Cramer also said that the study is an important contribution to the young field of proteomics research because there is little data on the important family of membrane-embedded proteins in the total protein database.

"Membrane proteins are involved in a cell's interactions with its environment, making them an essential component of metabolism," he said. "However, they are difficult to crystallise for study. This research could clarify our understanding of energy flow in human cells as well, giving us better insight into respiration and the absorption of antioxidants in animal cells."