Rational design of an efficient, genetically encodable, protein-encased singlet oxygen photosensitizer.

Singlet oxygen, O2(a1Δg), plays a key role in many processes of cell signaling. Limitations in mechanistic studies of such processes are generally associated with the difficulty of controlling the amount and location of O2(a1Δg) production in or on a cell. As such, there is great need for a system that (a) selectively produces O2(a1Δg) in appreciable and accurately quantifiable yields and (b) can be localized in a specific place at the suborganelle level. A genetically encodable, protein-encased photosensitizer is one way to achieve this goal. Through a systematic and rational approach involving mutations to a LOV2 protein that binds the chromophore flavin mononucleotide (FMN), we have developed a promising photosensitizer that overcomes many of the problems that affect related systems currently in use. Specifically, by decreasing the extent of hydrogen bonding between FMN and a specific amino acid residue in the local protein environment, we decrease the susceptibility of FMN to undesired photoinitiated ...