PT  - JOURNAL ARTICLE
AU  - Yun, Ji-Hye
AU  - Ohki, Mio
AU  - Park, Jae-Hyun
AU  - Ishimoto, Naito
AU  - Sato-Tomita, Ayana
AU  - Lee, Wonbin
AU  - Jin, Zeyu
AU  - Tame, Jeremy R. H.
AU  - Shibayama, Naoya
AU  - Park, Sam-Yong
AU  - Lee, Weontae
TI  - Pumping mechanism of NM-R3, a light-driven bacterial chloride importer in the rhodopsin family
AID  - 10.1126/sciadv.aay2042
DP  - 2020 Feb 01
TA  - Science Advances
PG  - eaay2042
VI  - 6
IP  - 6
4099  - http://advances.sciencemag.org/content/6/6/eaay2042.short
4100  - http://advances.sciencemag.org/content/6/6/eaay2042.full
SO  - Sci Adv2020 Feb 01; 6
AB  - A newly identified microbial rhodopsin, NM-R3, from the marine flavobacterium Nonlabens marinus, was recently shown to drive chloride ion uptake, extending our understanding of the diversity of mechanisms for biological energy conversion. To clarify the mechanism underlying its function, we characterized the crystal structures of NM-R3 in both the dark state and early intermediate photoexcited states produced by laser pulses of different intensities and temperatures. The displacement of chloride ions at five different locations in the model reflected the detailed anion-conduction pathway, and the activity-related key residues—Cys105, Ser60, Gln224, and Phe90—were identified by mutation assays and spectroscopy. Comparisons with other proteins, including a closely related outward sodium ion pump, revealed key motifs and provided structural insights into light-driven ion transport across membranes by the NQ subfamily of rhodopsins. Unexpectedly, the response of the retinal in NM-R3 to photostimulation appears to be substantially different from that seen in bacteriorhodopsin.