Filming proteins in action
French researchers have produced a film of proteins at work by freezing them in different states. They made a movie of an enzyme called "superoxide reductase" which is found in bacteria. This enzyme is a protein that catalyses chemical reactions and needs to eliminate some toxic molecules in order to survive. Besides discovering how this enzyme -- and others -- work, the real success for these researchers was to image how they fight for their lives.
The French team was composed of researchers of the Institut de Biologie Structurale (IBS) and the European Synchrotron Radiation Facility (ESRF), both located in Grenoble.
The film the researchers made "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)." (Credit: Gergely Katona, IBS). Here is a link to a larger version of this image that I've reframed for space reasons on this post.
The film was produced at the ESRF-IBS Cryobench Laboratory to freeze the protein in three different states while the reaction took place.
In order to make sure that they "trapped" the right intermediate states, the researchers used the technique of Raman spectroscopy. This technique provided them with strong evidence that the states were the appropriate ones by showing them the chemical bonds in each stage of the reaction. Once they had identified the right states, they studied the sample with synchrotron X-rays. "We expect this new methodology to be of use for many researchers in the field," explains Dominique Bourgeois[, one of the researchers.]
This research work has been published by Science under the name "Raman-Assisted Crystallography Reveals End-On Peroxide Intermediates in a Nonheme Iron Enzyme" (Volume 316, Issue 5823, Pages 449-453, April 20, 2007). For those of you who are curious, 'nonheme' iron is a dietary iron obtained from vegetable foods while 'heme' iron is dietary iron obtained from meat or blood products. According to what I've read somewhere, heme iron comes from the pigment heme which gives blood its deep red color.
Here are two links to the abstract of this technical paper and to a QuickTime movie available from the supporting online material provided by Science.
Sources: European Synchrotron Radiation Facility (ESRF) news release, April 20, 2007; and various websites
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