Early-stage dynamics of chloride ion-pumping rhodopsin revealed by a femtosecond X-ray laser

Proc Natl Acad Sci U S A. 2021 Mar 30;118(13):e2020486118. doi: 10.1073/pnas.2020486118.

Abstract

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.

Keywords: X-ray free-electron laser; light-driven chloride-pumping rhodopsin; serial femtosecond crystallography; time-resolved crystallography.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Video-Audio Media

MeSH terms

  • Cations, Monovalent / metabolism
  • Chloride Channels / isolation & purification
  • Chloride Channels / metabolism*
  • Chloride Channels / radiation effects
  • Chloride Channels / ultrastructure
  • Chlorides / metabolism*
  • Crystallography / methods
  • Electromagnetic Radiation
  • Lasers
  • Molecular Dynamics Simulation
  • Nocardioides
  • Protein Conformation, alpha-Helical / radiation effects
  • Protein Structure, Tertiary / radiation effects
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / radiation effects
  • Recombinant Proteins / ultrastructure
  • Retinaldehyde / metabolism
  • Retinaldehyde / radiation effects
  • Rhodopsins, Microbial / isolation & purification
  • Rhodopsins, Microbial / metabolism*
  • Rhodopsins, Microbial / radiation effects
  • Rhodopsins, Microbial / ultrastructure
  • Water / metabolism

Substances

  • Cations, Monovalent
  • Chloride Channels
  • Chlorides
  • Recombinant Proteins
  • Rhodopsins, Microbial
  • Water
  • Retinaldehyde

Supplementary concepts

  • Nocardioides marinus