A novel light-driven chloride-pumping rhodopsin (ClR) containing an NTQ motif' in its putative ion conduction pathway has been discovered and functionally characterized in a genomic analysis study of a marine bacterium. Here we report the crystal structure of ClR from the flavobacterium Nonlabens marinus S1-08 T determined under two conditions at 2.0 and 1.56 Å resolutions. The structures reveal two chloride-binding sites, one around the protonated Schiff base and the other on a cytoplasmic loop. We identify a 3 omega motif' formed by three non-consecutive aromatic amino acids that is correlated with the B-C loop orientation. Detailed ClR structural analyses with functional studies in E. coli reveal the chloride ion transduction pathway. Our results help understand the molecular mechanism and physiological role of ClR and provide a structural basis for optogenetic applications.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation (NRF-2016R1A2B2013305 to H.S.C.; NRF-2011-0017670 and NRF-2014M3C9A3068822 to J.F.K.; and NRF-2013R1A2A2A01068963 to W.L.) of the Ministry of Science, ICT and Future Planning, and the Strategic Initiative for Microbiomes in Agriculture of the Ministry of Agriculture, Food and Rural Affairs, Republic of Korea. The work was supported in part by Brain Korea 21 (BK21) PLUS program/S.-K.K., S.-H.J., J.S.C. and H.K. are fellowship awardees of BK21 PLUS program.
All Science Journal Classification (ASJC) codes
- Biochemistry, Genetics and Molecular Biology(all)
- Physics and Astronomy(all)