Catching proteins in the act
August 22, 2016Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography
Serial femtosecond crystallography (SFX) using X-ray free-electron laser sources is an emerging method with considerable potential for time-resolved pump-probe experiments. Here we present a lipidic cubic phase SFX structure of the light-driven proton pump bacteriorhodopsin (bR) to 2.3 Å resolution and a method to investigate protein dynamics with modest sample requirement. Time-resolved SFX (TR-SFX) with a pump-probe delay of 1 ms yields difference Fourier maps compatible with the dark to M state transition of bR. Importantly, the method is very sample efficient and reduces sample consumption to about 1 mg per collected time point. Accumulation of M intermediate within the crystal lattice is confirmed by time-resolved visible absorption spectroscopy. This study provides an important step towards characterizing the complete photocycle dynamics of retinal proteins and demonstrates the feasibility of a sample efficient viscous medium jet for TR-SFX.
Figure. In side view (a) and perpendicular to the membrane (b). The retinal is shown as yellow sticks and the Lys216 side chain covalently binding retinal as blue sticks. Continuous 2Fo−Fc electron density map around retinal and lysine is shown in magenta. Helices A–G are defined based on the header of pdb entry 1QHJ.
Reference: Nogly, P., V. Panneels, G. Nelson, C. Gati, T. Kimura, C. Milne, D. Milathianaki, M. Kubo, W. Wu, C. Conrad, J. Coe, R. Bean, Y. Zhao, P. Båth, R. Dods, R. Harimoorthy, K. R. Beyerlein, J. Rheinberger, D. James, D. DePonte, C. Li, L. Sala, G. J. Williams, M. S. Hunter, J. E. Koglin, P. Berntsen, E. Nango, S. Iwata, H. N. Chapman, P. Fromme, M. Frank, R. Abela, S. Boutet, A. Barty, T. A. White, U. Weierstall, J. Spence, R. Neutze, G. Schertler and J. Standfuss (2016). Lipidic cubic phase injector is a viable crystal delivery system for time-resolved serial crystallography. Nature Commun. 7: 12314. 10.1038/ncomms12314 Nogly-2016 (1.87 MB).
Also see the the ScienceDaily article
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