pAceR is a positive polarity fluorescent voltage sensor (shows an increase in fluorescence during voltage depolarization events). It consists of a voltage-sensitive rhodopsin sequence fused via a linker to the fluorescent mRuby3 protein. pAceR was generated by mutagenesis of VARNAM2, containing in addition the mutations R78E, S81D and D92N (PMID:36378956). For detailed kinetic and spectral properties and a comparison of pAceR with other fluorescent voltage indicators, see PMID:36378956.