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Most protein research looks only at these biological macromolecules at rest, but most of the interesting behaviour is dynamic. Now, researchers at the ESRF and the Institut de Biologie Structural (IBS) have used Raman and other techniques to create a protein movie so they can do a freeze-frame analysis of proteins in different states. Dominique Bourgeois and his colleagues have investigated a protein involved in the bacterial elimination of free radicals - superoxide reductase. This enzyme is an essential weapon in ongoing battle faced by all living organisms against oxidative stress, the side effect of oxygen metabolism. In humans, about 2% of the oxygen we inhale forms the toxic superoxide radical.Levels are higher in sufferers of neurodegenerative diseases such as Alzheimer's disease, which worsens symptoms. Scientists are keen to find drugs to enhance the superoxide elimination process and understanding the enzymes involved in their breakdown could provide important clues in this endeavour. The team used the ESRF-IBS "Cryobench" laboratory to freeze the protein in three different states while the reaction took place. They used Raman spectroscopy to ensure they were snapping the proteins in intermediate states suitable for study. Once they had identified the right states, they used synchrotron X-rays to snap the frozen action, building up a sequence of protein states to generate a kind of stop-motion "movie". "The achievement of this research is twofold," Bourgeois explains, "on one side there is the technological success of filming an enzyme in action and on the other hand there are the results that contribute to the knowledge of how this enzyme works." Bourgeois adds that the new methodology could be used by researchers investigating other proteins, including the more complex human version of superoxide reductase. Techniques aside, the current data suggest a possible mechanism for hydrogen peroxide formation, say the researchers. The study highlights the role of a key water molecule finely controlled by the enzyme dynamics and reveals conformational transitions that can now be used for additional computational modelling and structural investigations. Such studies will not only help us understand the role played by this enzyme in the metabolism of superoxide but could lead to the design of biomimetic catalysts. Related links:
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Raman in the movies |
