Visualising ultrafast structural changes in photosynthetic reaction centres

Wednesday, March 6, 2013 - 3:00pm

Richard Neutze, University of Gothenburg

X-ray free electron laser (XFEL) radiation is revolutionizing experimental approaches to structural biology. One area where XFEL radiation is expected to have a large impact is time-resolved structural studies of protein conformational changes. As one example, the LCLS has the potential to provide completely new structural insights into fundamental mechanisms of energy transduction in nature by visualizing structural changes in photosynthetic membrane protein complexes. I will introduce time-resolved structural biology by presenting structural results from time-resolved Laue diffraction studies of a photosynthetic reaction centre performed using synchrotron radiation1. I will then use the same integral membrane protein complex to illustrate serial femtosecond crystallography2-5: a new approach to structural biology that has been developed through collaboration between groups from the LCLS, Arizona State University, DESY and the University of Hamburg, Heidelberg MPI, and the University of Gothenburg. The key experimental advantages of time-resolved serial femtosecond crystallography (TR-SFX) at an XFEL relative to Laue diffraction approaches using synchrotron radiation will be described. Finally, I will describe Time-Resolved Wide Angle X-ray Scattering (TR-WAXS), a direct structural method for probing protein conformational changes in solution. I will present results from the LCLS using TR-WAXS to observe ultrafast structural changes in photosynthetic reaction centres. In this work we observed a “protein quake” whereby the protein reacts through rapid structural changes in response to the input of energy into buried chromophores. These protein structural changes arose on a time scale of picoseconds and were damped within tens of picoseconds. 

1    Wohri, A. B. et al. Light-induced structural changes in a photosynthetic reaction center caught by Laue diffraction. Science 328, 630-633 (2010).

2    Chapman, H. et al. Femtosecond X-ray protein nanocrystallography. Nature 470, 73-77 (2011).

3    Johansson, L. C. et al. Lipidic phase membrane protein serial femtosecond crystallography. Nature Methods 9, 263-265 (2012).

4    Redecke, L. et al. Natively inhibited Trypanosoma brucei cathepsin B structure determined by using an X-ray laser. Science 339, 227-230 (2013).

5    Boutet, S. et al. High-resolution protein structure determination by serial femtosecond crystallography. Science 337, 362-364 (2012).

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