Kato, H.E. et al. Nature 482, 369–374 (2012).

The neuroscience community has enthusiastically embraced channelrhodopsin 2 (ChR2)—and its now many variants—as a tool with unique capability to control neuron activity using light with high temporal and spatial precision. Properties of the original ChR2 have been tailored and improved by targeted mutagenesis, but mutations have so far been largely chosen based on the well-studied bateriorhodopsin, a relative of ChR2. Unfortunately, the two proteins are only partially homologous. Now Kato et al. resolve the crystal structure of a channelrhodopsin chimera (chimera of ChR1 and ChR2) at 2.3-angstrom resolution. The structure revealed the unique architecture of channelrhodopsins and will be a very valuable tool for the design of new optogenetic tools.