De Novo Designed Porphyrin-Binding Proteins Photocatalyze the Nitrogen Reduction Reaction.

In this work, we de novo designed a two-helix α-helical protein capable of forming dimers, which features a central cavity that accommodates porphyrin molecules. The resulting porphyrin-binding protein, formed by mixing the porphyrin with the dimer protein, exhibits visible-light-driven catalytic activity for the nitrogen reduction reaction. To further optimize the protein, we selected three mutation layers and predicted their structures. From these, we identified seven mutants that retained the original protein folding structure, which are used for the photocatalytic ammonia production from nitrogen after binding porphyrin. Among them, the best-performing mutant achieved a catalytic rate of 9.704 mg gcat-1 h-1 for ammonia synthesis, which is higher than most of the current reported artificial catalysts. This work provides a promising strategy for the de novo design of porphyrin-binding proteins as catalysts for nitrogen fixation under mild conditions.