Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 119, Issue 9, Pages -Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2117433119
Keywords
microbial rhodopsin; serial femtosecond crystallography; chloride ion pump
Categories
Funding
- MEXT/JSPS KAKENHI [17K07324, 20H05450, 19H05784, 19H05776, 18H02394, 21H02439]
- Japan Agency for Medical Research and Development [JP21am0101070]
- RIKEN (pioneering project Dynamic Structural Biology)
- Grants-in-Aid for Scientific Research [20H05450, 21H02439, 19H05776, 19H05784, 18H02394, 17K07324] Funding Source: KAKEN
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Time-resolved serial femtosecond crystallography was used to study the structural changes and ion transfer mechanisms in anion-pumping rhodopsins. The study revealed the conformational alterations during ion transfer and ion release, as well as the halide binding site for ion transfer.
Light-driven chloride-pumping rhodopsins actively transport anions, including various halide ions, across cell membranes. Recent studies using time-resolved serial femtosecond crystallography (TR-SFX) have uncovered the structural changes and ion transfer mechanisms in light-driven cation-pumping rhodopsins. However, the mechanism by which the conformational changes pump an anion to achieve unidirectional ion transport, from the extracellular side to the cytoplasmic side, in anion-pumping rhodopsins remains enigmatic. We have collected TR-SFX data of Nonlabens marinus rhodopsin-3 (NM-R3), derived from a marine flavobacterium, at 10-mu s and 1-ms time points after photoexcitation. Our structural analysis reveals the conformational alterations during ion transfer and after ion release. Movements of the retinal chromophore initially displace a conserved tryptophan to the cytoplasmic side of NM-R3, accompanied by a slight shift of the halide ion bound to the retinal. After ion release, the inward movements of helix C and helix G and the lateral displacements of the retinal block access to the extracellular side of NM-R3. Anomalous signal data have also been obtained from NM-R3 crystals containing iodide ions. The anomalous density maps provide insight into the halide binding site for ion transfer in NM-R3.
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