Conformational alterations in unidirectional ion transport of a light-driven chloride pump revealed using X-ray free electron lasers
Toshiaki Hosaka, Takashi Nomura, Minoru Kubo, Takanori Nakane, Fangjia Luo, Shun‐ichi Sekine, Takuhiro Ito, Kazutaka Murayama, Kentaro Ihara, Haruhiko Ehara, Kazuhiro Kashiwagi, Kazushige Katsura, Ryogo Akasaka, Tamao Hisano, Tomoyuki Tanaka, Rie Tanaka, Toshi Arima, A. Yamashita, Michihiro Sugahara, Hisashi Naitow, Yoshinori Matsuura, Susumu Yoshizawa, Kensuke Tono, Shigeki Owada, Osamu Nureki, Tomomi Kimura‐Someya, So Iwata, Eriko Nango, Mikako Shirouzu
Abstract
rhodopsin-3 (NM-R3), derived from a marine flavobacterium, at 10-µs 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.