Molecular determinants differentiating photocurrent properties of two channelrhodopsins from Chlamydomonas

Hongxia Wang, Yuka Sugiyama, Takuya Hikima, Eriko Sugano, Hiroshi Tomita, Tetsuo Takahashi, Toru Ishizuka, Hiromu Yawo

    Research output: Contribution to journalArticle

    126 Citations (Scopus)

    Abstract

    A light signal is converted into an electrical one in a single molecule named channelrhodopsin, one of the archaea-type rhodopsins in unicellular green algae. Although highly homologous, two molecules of this family, channelrhodopsin-1 (ChR1) and -2 (ChR2), are distinct in photocurrent properties such as the wavelength sensitivity, desensitization, and turning-on and -off kinetics. However, the structures regulating these properties have not been completely identified. Photocurrents were analyzed for several chimera molecules made by replacing N-terminal segments of ChR2 with the homologous counterparts of ChR1. We found that the wavelength sensitivity of the photocurrent was red-shifted with negligible desensitization and slowed turning-on and -off kinetics when replacement was made with the segment containing the fifth transmembrane helix of ChR1. Therefore, this segment is involved in the determination of photocurrent properties, the wavelength sensitivity, and the kinetics characterizing ChR1 and ChR2. Eight amino acid residues differentiating this segment were exchanged one-by-one, and the photocurrent properties of each targeted mutant ChR2 were further analyzed. Among them, position Tyr226(ChR1)/ Asn187(ChR2) is one of the molecular determinants involved in the wavelength sensitivity, desensitization, and turning-on and -off kinetics. It is suggested that these amino acid residues directly or indirectly interact with the chromophore as well as with the protein structure determining the photocurrent kinetics. Some of the chimera channelrhodopsins are suggested to have several advantages over the wild-type ChR2 in the introduction of light-induced membrane depolarization for the purpose of artificial stimulation of neurons in vivo and visual prosthesis for photoreceptor degeneration.

    Original languageEnglish
    Pages (from-to)5685-5696
    Number of pages12
    JournalJournal of Biological Chemistry
    Volume284
    Issue number9
    DOIs
    Publication statusPublished - 2009 Feb 27

    ASJC Scopus subject areas

    • Biochemistry
    • Molecular Biology
    • Cell Biology

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  • Cite this

    Wang, H., Sugiyama, Y., Hikima, T., Sugano, E., Tomita, H., Takahashi, T., Ishizuka, T., & Yawo, H. (2009). Molecular determinants differentiating photocurrent properties of two channelrhodopsins from Chlamydomonas. Journal of Biological Chemistry, 284(9), 5685-5696. https://doi.org/10.1074/jbc.M807632200