KillerRed (KR)

KillerRed is a dimeric red fluorescent protein derived from the hydrozoan jellyfish chromoprotein anm2CP, specifically engineered to function as a genetically encoded photosensitizer (Bulina et al., 2006). Unlike standard fluorescent proteins, it features a unique water-filled channel that allows molecular oxygen to reach the chromophore, facilitating the production of reactive oxygen species (ROS) such as superoxide upon green light irradiation (Carpentier et al., 2009; Pletnev et al., 2009). This light-induced ROS generation enables the precise destruction of specific cells or the inactivation of fusion proteins through chromophore-assisted light inactivation (CALI) (Waldeck et al., 2009; Jarvela & Linstedt, 2014). While primarily used as a research tool to study protein function and oxidative stress, KillerRed has been explored for potential applications in photodynamic therapy (PDT) for cancer (Bulina et al., 2006; Vegh et al., 2011). However, it is not a traditional therapeutic target like a receptor or enzyme; rather, it serves as an effector molecule or an experimental agent (Evrogen, 2024). Its use is characterized by high phototoxicity and specificity, though challenges such as dimerization and limited light penetration in tissues remain (Takemoto et al., 2013). In disease research, it has been employed to create models of retinal degeneration and to study the mechanisms of cell senescence and apoptosis (Tezuka et al., 2016; Shcherbo et al., 2009).

Other names

KillerRed fluorescent proteinGenetically encoded photosensitizerKR

KillerRed generates reactive oxygen species (ROS), primarily superoxide and hydrogen peroxide, upon irradiation with green light (540-590 nm) through a Type I photoreaction facilitated by a unique water-filled channel reaching the chromophore (Bulina et al., 2006; Carpentier et al., 2009).