title: The DC gate in Channelrhodopsin-2: crucial hydrogen bonding interaction between C128 and D156.
abstract: The light-gated cation channel Channelrhodopsin-2 (ChR2), a retinylidene protein found in the eye-spot of Chlamydomonas reinhardtii, became an optogenetic tool to trigger neurophysiological responses by light and, thus, revolutionized spatio-temporal studies of such processes. The reaction mechanism still remains elusive but recent vibrational spectroscopic experiments started to resolve details of the associated structural changes during the photocycle. Large alterations in the polypeptide backbone were observed by FT-IR spectroscopy that precede and succeed the opening and closing of the channel, respectively. However, the molecular switch that controls gating is still unknown. Here, we present difference spectra of the D156E mutant of ChR2 and assign the observed vibrational bands to crucial hydrogen bonding changes of this residue in various intermediate states of the photoreaction. By comparison with spectra of wild-type ChR2 and the C128T mutant and correlation to electrophysiological studies, we propose the DC gate as a crucial hydrogen-bonding interaction between D156 and C128 which may represent the valve of the channel.
authors.affiliation: Freie Universität Berlin, Department of Physics, Arnimallee 14, 14195, Berlin, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Nack
authors.forename: Ionela
authors.initials: I
authors.lastname: Radu
authors.forename: Michael
authors.initials: M
authors.lastname: Gossing
authors.forename: Christian
authors.initials: C
authors.lastname: Bamann
authors.forename: Ernst
authors.initials: E
authors.lastname: Bamberg
authors.forename: Gabriele Fischer
authors.initials: GF
authors.lastname: von Mollard
authors.forename: Joachim
authors.initials: J
authors.lastname: Heberle
mesh_terms: D020418:Algal Proteins / Q000737:chemistry* / Q000235:genetics; D019943:Amino Acid Substitution; D001224:Aspartic Acid / Q000737:chemistry*; D016825:Chlamydomonas reinhardtii / Q000737:chemistry; D003553:Cystine / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry; D006860:Hydrogen Bonding; D007473:Ion Channels / Q000737:chemistry* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D020418:Algal Proteins; D007473:Ion Channels; D011994:Recombinant Proteins; D001224:Aspartic Acid; D018698:Glutamic Acid; D003553:Cystine