Iron-Sulfur Peptides Mimicking Ferredoxin for an Efficient Electron Transfer to Hydrogenase

In the green alga Chlamydomonas reinhardtii, hydrogenase HydA1 converts protons and electrons to H₂ at the H-cluster, which includes a [4Fe-4S] cluster linked to a [2Fe] cluster. The yield of H₂ is limited by the electron transfer to HydA1, mediated by the iron-sulfur unit of a photosynthetic electron transfer ferredoxin (PetF). In this study, I have investigated by molecular dynamics and the hybrid quantum mechanics/molecular mechanics method two canonical iron-sulfur peptides (PM1 and F_BM) that hold potential as PetF replacements. Using a docking approach, I predict that the distance between the two iron-sulfur clusters in F_BM/HydA1 is shorter than in PM1/HydA1, ensuring a greater electron transfer rate. This finding is in line with the reported higher H₂ production rates for F_BM/HydA1. I also show that the redox potential of these peptides, and therefore their electron transfer properties, can be changed by single-residue mutations in the secondary coordination sphere of their cluster. In particular, I have designed a PM1 variant that disrupts the hydrogen-bonding network between water and the cluster, shifting the redox potential negatively compared to PM1. These results will guide experiments aimed at replacing PetF with peptides that can unlock the biotechnological potential of the alga.