Switching Type I/Type II Reactions by Turning a Photoredox Catalyst into a Photo-Driven Artificial Metalloenzyme

While photocatalysts have been recognized as powerful and environmentally friendly catalysts, harnessing their reactivity still remains challenging. On account of the distinctive reaction compartment that their protein scaffolds provide for the incorporated metal complex, artificial metalloenzymes (ArMs) can improve catalytic reaction rates and stereochemical selectivity. In the present study, we have developed a photo-driven ArM by incorporating a DNA photo-switch metal complex, [Ru(bpy)2dppz]2+ (1), into an apo-form riboflavin-binding protein (RFBP). We report that two potentially competing photocatalytic reaction pathways, i.e., a photoredox reaction and an energy transfer reaction, can be switched by 1 alone and by the ArM. This reaction switching was exploited in selective protein labeling; 1 alone preferentially promotes tyrosine modification, while the ArM promotes histidine modification. The present study thus opens the door for the potential use of ArMs to control the reactivity of photocatalysts.