WiChR(T95C) is an engineered kalium channelrhodopsin (KCR) that can be used as an optogenetic tool to induce membrane hyperpolarization and inhibit neuron activity. It corresponds to the light-gated KCR encoded by the Wobblia lunata ChR gene, into which a T95C mutation amino acid substitution has been introduced (this results in a slightly more negative reversal potential and faster kinetics). The formation of a functional channel requires the presence of a covalently linked all-trans-retinal chromophore which can be provided exogenously if necessary via the culture medium or diet (this cofactor is present endogenously in some intact vertebrate systems). For detailed kinetic and spectral properties, see FBrf0264505.