Photo-oxidation of tyrosine in a bio-engineered bacterioferritin 'reaction centre'-A protein model for artificial photosynthesis

Light-induced electron transfer from proximal tyrosine residues to the photo-oxidised ZnCe6
- +, in the modified BFR reconstituted with both ZnCe6 and MnII, is presented. Three site-specific tyrosine variants (Y25F, Y58F and Y45F) were made to localise the redox-active tyrosine in the engineered system. The results indicate that: presence of bound MnII is necessary to observe tyrosine oxidation in all BFR variants; Y45 the most important tyrosine as an immediate electron donor to the oxidised ZnCe6
- + and that Y25 and Y58 are both redox-active in this system, but appear to function interchangebaly. High-resolution (2.1 Å) crystal structures of the tyrosine variants show that there are no mutation-induced effects on the overall 3-D structure of the protein. Small effects are observed in the Y45F variant. Here, the BFR-RC represents a protein model for artificial photosynthesis.