title: Projection structure of channelrhodopsin-2 at 6 Å resolution by electron crystallography.
abstract: Channelrhodopsin-2 (ChR2) is the prototype of a new class of light-gated ion channels that is finding widespread applications in optogenetics and biomedical research. We present a 6-Å projection map of ChR2, obtained by cryo-electron microscopy of two-dimensional crystals grown from pure, heterologously expressed protein. The map shows that ChR2 is the same dimer with non-crystallographic 2-fold symmetry in three different membrane crystals. This is consistent with biochemical analysis, which shows a stable dimer in detergent solution. Comparison to the projection map to bacteriorhodopsin indicates a similar structure of seven transmembrane alpha helices. Based on the projection map and sequence alignments, we built a homology model of ChR2 that potentially accounts for light-induced channel gating. Although a monomeric channel is not ruled out, comparison to other membrane channels and transporters suggests that the ChR2 channel is located at the dimer interface on the 2-fold axis, lined by transmembrane helices 3 and 4.
authors: Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Straße 3, 60438 Frankfurt, Germany.
authors: Maria
authors: M
authors: Müller
authors: Christian
authors: C
authors: Bamann
authors: Ernst
authors: E
authors: Bamberg
authors: Werner
authors: W
authors: Kühlbrandt
mesh_terms: D000595:Amino Acid Sequence; D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000378:metabolism; D000075402:Channelrhodopsins; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D006801:Humans; D007473:Ion Channels / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid
chemical_list: D000075402:Channelrhodopsins; D007473:Ion Channels; D009419:Nerve Tissue Proteins; D001436:Bacteriorhodopsins