The DC gate in Channelrhodopsin-2: crucial hydrogen bonding interaction between C128 and D156.
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.
Nack
Melanie
M
Freie Universität Berlin, Department of Physics, Arnimallee 14, 14195, Berlin, Germany.
Radu
Ionela
I
Gossing
Michael
M
Bamann
Christian
C
Bamberg
Ernst
E
von Mollard
Gabriele Fischer
GF
Heberle
Joachim
J
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
D020418:Algal Proteins; D007473:Ion Channels; D011994:Recombinant Proteins; D001224:Aspartic Acid; D018698:Glutamic Acid; D003553:Cystine