GtACR2 corresponds to the light-gated anion channel encoded by the Guillardia theta ACR2 gene (GB_protein:XP_005821982). It can be used as an optogenetic tool to produce membrane hyperpolarization and inhibit neuron activity; it strictly conducts anions, shows rapid response kinetics, and requires low light intensity for activation. The maximal sensitivity of the protein is to 470nm light (PMID:26113638).