{
    "abstract": "Parvularcula oceani xenorhodopsin is the first light-driven inward proton pump. To understand the mechanism of inward proton transport, comprehensive transient absorption spectroscopy was conducted. Ultrafast pump-probe spectroscopy revealed that the isomerization time of retinal is 1.2 ps, which is considerably slower than those of other microbial rhodopsins (180-770 fs). Following the production of J, the K intermediate was formed at 4 ps. Proton transfer occurred on a slower timescale. Proton release and uptake were observed on the L/M-to-M and M decay, respectively, by monitoring transient absorption changes of pH-indicating dye, pyranine. Although a proton was released from Asp216 into the cytoplasmic medium, no proton-donating residue was identified on the extracellular side in mutation experiments. We revealed that a branched retinal isomerization (from 13-cis-15-anti to 13-cis-15-syn and all-trans-15-anti) occurred simultaneously with proton uptake. Furthermore, although the proton release showed a large kinetic isotope effect (KIE), the KIE of proton uptake was negligible. These results suggest that retinal isomerization is the rate-limiting process in proton uptake and that the regulation of p K",
    "authors": [
        {
            "affiliation": "PRESTO, Japan Science and Technology Agency , 4-1-8 Honcho , Kawaguchi , Saitama 332-0012 , Japan.",
            "firstname": "Keiichi",
            "initials": "K",
            "lastname": "Inoue"
        },
        {
            "affiliation": "Molecular Spectroscopy Laboratory, RIKEN , 2-1 Hirosawa , Wako 351-0198 , Japan.",
            "firstname": "Shinya",
            "initials": "S",
            "lastname": "Tahara"
        },
        {
            "affiliation": null,
            "firstname": "Yoshitaka",
            "initials": "Y",
            "lastname": "Kato"
        },
        {
            "affiliation": "Molecular Spectroscopy Laboratory, RIKEN , 2-1 Hirosawa , Wako 351-0198 , Japan.\nUltrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN , 2-1 Hirosawa , Wako 351-0198 , Japan.",
            "firstname": "Satoshi",
            "initials": "S",
            "lastname": "Takeuchi"
        },
        {
            "affiliation": "Molecular Spectroscopy Laboratory, RIKEN , 2-1 Hirosawa , Wako 351-0198 , Japan.\nUltrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN , 2-1 Hirosawa , Wako 351-0198 , Japan.",
            "firstname": "Tahei",
            "initials": "T",
            "lastname": "Tahara"
        },
        {
            "affiliation": null,
            "firstname": "Hideki",
            "initials": "H",
            "lastname": "Kandori"
        }
    ],
    "conclusions": null,
    "copyrights": null,
    "doi": "10.1021/acs.jpcb.8b01279",
    "journal": "The journal of physical chemistry. B",
    "keywords": [],
    "methods": null,
    "publication_date": "2018-05-29",
    "pubmed_id": "29807427",
    "results": null,
    "title": "Spectroscopic Study of Proton-Transfer Mechanism of Inward Proton-Pump Rhodopsin, Parvularcula oceani Xenorhodopsin.",
    "xml": "<Element 'PubmedArticle' at 0x788504b8b8d0>"
}