A blue-shifted anion channelrhodopsin from the Colpodellida alga Vitrella brassicaformis

Microbial rhodopsins, a family of photoreceptive membrane proteins containing the chromophore retinal, show a variety of light-dependent molecular functions. Channelrhodopsins work as light-gated ion channels and are widely utilized for optogenetics, which is a method for controlling neural activities by light. Since two cation channelrhodopsins were identified from the chlorophyte alga Chlamydomonas reinhardtii, recent advances in genomic research have revealed a wide variety of channelrhodopsins including anion channelrhodopsins (ACRs), describing their highly diversified molecular properties (e.g., spectral sensitivity, kinetics and ion selectivity). Here, we report two channelrhodopsin-like rhodopsins from the Colpodellida alga Vitrella brassicaformis, which are phylogenetically distinct from the known channelrhodopsins. Spectroscopic and electrophysiological analyses indicated that these rhodopsins are green- and blue-sensitive pigments (lambda(max) = similar to 550 and similar to 440 nm) that exhibit light-dependent ion channeling activities. Detailed electrophysiological analysis revealed that one of them works as a monovalent anion (Cl-, Br- and NO3-) channel and we named it V. brassicaformis anion channelrhodopsin-2, VbACR2. Importantly, the absorption maximum of VbACR2 (similar to 440 nm) is blue-shifted among the known ACRs. Thus, we identified the new blue-shifted ACR, which leads to the expansion of the molecular diversity of ACRs.

The version of record of this article, first published in Scientific Reports, is available online at Publisher’s website: http://dx.doi.org/10.1038/s41598-023-34125-8