rsEGFP2 is a monomeric protein that can be reversibly switched between a green fluorescent state and a non-fluorescent state: exposure to light of around 480nm quenches the fluorescence, while irradiation at around 405nm restores the green fluorescence. The green fluorescent state has a major excitation peak of 478nm which results in emission with a peak of 503nm. rsEGFP2 contains the mutations T65A, Q69L, V163S, A206K compared to EGFP (PMID:23330067).