Involvement of glutamate 97 in ion influx through photo-activated channelrhodopsin-2

Saki Tanimoto, Yuka Sugiyama, Tetsuo Takahashi, Toru Ishizuka, Hiromu Yawo

    Research output: Contribution to journalArticlepeer-review

    14 Citations (Scopus)

    Abstract

    The light absorption of a channelrhodopsin-2 (ChR2) is followed by conformational changes to the molecule, which allows the channel structure to become permeable to cations. Previously, a single point mutation in ChR2, which replaces glutamate residue 97 with a nonpolar alanine (E97A), was found to attenuate the photocurrent, suggesting that the E97 residue is involved in ion flux regulation. Here, the significance of E97 and its counterpart ChR1 (E136) were extensively studied by mutagenesis, whereby we replaced these glutamates with aspartate (D), glutamine (Q) or arginine (R). We found that the charge at this position strongly influences ion permeation and that the photocurrents were attenuated in the order of ChR2>E97D≈E97Q>E97R. We observed similar results with our chimeric/synthetic/artificial construct, ChR-wide receiver (ChRWR), which contains the first to fifth transmembrane helices of ChR1. The E-to-Q or E-to-R mutations, but not the E-to-D mutation, strongly retarded the sensitivity to the Gd3+-dependent blocking of the ChR1 or ChR2 channels. Our results suggest that the glutamate residue at this position lies in the outer pore, where it interacts with a cation to facilitate dehydration, and that this residue is the primary binding target of Gd3+.

    Original languageEnglish
    Pages (from-to)13-22
    Number of pages10
    JournalNeuroscience Research
    Volume75
    Issue number1
    DOIs
    Publication statusPublished - 2013 Jan

    Keywords

    • Channel block
    • Channel pore
    • Channelrhodopsin
    • Gadolinium
    • Gd
    • Ion channel
    • La
    • Lanthanum
    • Optogenetics
    • Permeability
    • Rectification

    ASJC Scopus subject areas

    • Neuroscience(all)

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