Most of the research done on proteins is based on their study in a resting state and their study in movement is extremely limited due to technological limitations. Recently we have made a movie of an enzyme (a protein that catalyses chemical reactions) found in bacteria. The achievement of this research is two-fold: on one hand 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.
The film shows how the lysine amino acid (yellow part of the protein) grabs a water molecule (in blue) and imports it into the enzyme to perform the catalytic reaction on the superoxide (in red).
The enzyme filmed in action is called â€œsuperoxide reductaseâ€, its role is to eliminate a toxic molecule called â€œsuperoxide radicalâ€. In order to survive, all living organisms have to fight oxidative stress, produced by outflows of the oxygen metabolism. In humans, about 2% of the oxygen used to breathe is transformed into this toxic â€œsuperoxide radicalâ€ molecule, instead of water. This production is increased in people affected by neurodegenerative diseases such as Alzheimer. A high amount of these molecules worsen these illnesses, so it is important to look for drugs to eliminate them.
The enzyme studied we acts uniquely in bacteria and its counterpart in humans is more complex. Synthesizing an enzyme like this one through biomimetics is an exciting possibility for developing future drugs.
In order to produce the film, our team used the ESRF-IBS â€œCryobenchâ€ laboratory to freeze the protein in three different states while the reaction took place. In order to make sure that they â€œtrappedâ€ the right intermediate states, the we used the technique of Raman spectroscopy. This technique provided a strong evidence that the states were the appropriate ones by showing the chemical bonds in each stage of the reaction. Once the right states were identified, we studied the samples with synchrotron X-rays. We hope this new methodology to be of use for many researchers in the field.
Filming certain proteins while reactions occur has been possible at the ESRF for some years. However, until recently, experiments were restricted to proteins that can be excited by light and are very resistant in crystalline form.
Based on the popular science description by Montserrat Capellas, ESRF press officier