Chloride ion–pumping rhodopsin (ClR) in some marine bacteria utilizes light energy to actively transport Cl− into cells. How the ClR initiates the transport is elusive. Here, we show the dynamics of ion transport observed with time-resolved serial femtosecond (fs) crystallography using the Linac Coherent Light Source. X-ray pulses captured structural changes in ClR upon flash illumination with a 550 nm fs-pumping laser. High-resolution structures for five time points (dark to 100 ps after flashing) reveal complex and coordinated dynamics comprising retinal isomerization, water molecule rearrangement, and conformational changes of various residues. Combining data from time-resolved spectroscopy experiments and molecular dynamics simulations, this study reveals that the chloride ion close to the Schiff base undergoes a dissociation–diffusion process upon light-triggered retinal isomerization.
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - 2021 Mar 30|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS. The experiment was conducted at the LCLS, SLAC National Accelerator Laboratory, supported by the US Department of Energy, Office of Science, and Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. We would like to acknowledge all members of the PAL-XFEL with the support of Pohang Accelerator Laboratory, Korea. National Natural Science Foundation of China (Grant Nos. 31971136, 11575021, and U1930402 to H.L.; Grant Nos. 21773012 and U2032112 to W.Z.); National Research Foundation of Korea (Grant Nos. NRF-2019M3E5D6063903, 2017M3A9F6029753, and 2018K2A9A2A06024227 to W.L.; and NRF-2016R1A6A3A04010213 to J.-H.Y.); The STC Program of the NSF through BioXFEL under Agreement No. 1231306 (U.W., N.A.Z., J.C.H.S., and M.S.); and NSF ABI Innovations Award No. 1565180 (C.L., U.W., N.A.Z., and J.C.H.S.). NSF Grant No. 2030466 to M.S. Parts of the sample injector used at LCLS for this research were funded by the NIH, P41GM103393, formerly P41RR001209. J.R.H.T. received funding from Open-Eye Scientific Software.
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