[WS5] Non-equilibrium state molecular movies: a new frontier in structural and functional studies on proteins

[WS5-01] Pumping mechanism of NM-R3, a light-driven bacterial chloride importer in the rhodopsin family

Mio Ohki¹, Ji-Hye Yun², Naoya Shibayama³, Weontae Lee², ^○Sam-Yong Park¹ (1.Grad. Sch. of Med. Life Science, Yokohama City Univ., 2.Dept. of Biochem., Yonsei Univ., 3.Jichi Med. Univ.)

A novel 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 photo-excited states produced by laser pulses of different intensities and temperatures. The displacement of chloride ions at different locations in the model reflected the detailed anion-conduction pathway and key residues 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.