RubyACRs, nonalgal anion channelrhodopsins with highly red-shifted absorption
Elena G. Govorunova, Oleg A. Sineshchekov, Hai Li, Yumei Wang, Leonid S. Brown, John L. Spudich
Abstract
Significance Our identification and characterization of two anion channelrhodopsins families, one from nonphotosynthetic microorganisms, shows that light-gated anion conductance is more widely spread among eukaryotic lineages than previously thought. The strongly red-shifted absorption spectra of the subset that we designate RubyACRs make them promising candidates for the long-sought inhibitory optogenetic tools producing large passive currents activated by red light, enabling deep tissue penetration. Previously only low-efficiency ion-pumping rhodopsins were available for neural inhibition at similar long wavelengths. The unusual residue composition of the retinal-binding pocket in RubyACRs expands our understanding of color tuning in rhodopsins. Finally, activation of chloride currents by energy transfer from a cytoplasmic fluorescent tag on RubyACRs introduces a potential dimension in molecular engineering of optogenetic tools.