Fundamental Electrostatics Explains Why Ferredoxin- and HiPIP-Type Proteins Favor Different Redox Transitions in [4Fe-4S]-Cys 4 Clusters

[4Fe-4S] clusters in proteins typically occur in three distinct redox states: the oxidized state ([4Fe-4S]³⁺), the semireduced state ([4Fe-4S]²⁺), and the reduced state ([4Fe-4S]¹⁺). Consequently, proteins containing these clusters could exhibit two distinct redox transitions: the low-potential transition (LPT: [4Fe-4S]¹⁺/[4Fe-4S]²⁺) and the high-potential transition (HPT: [4Fe-4S]²⁺/[4Fe-4S]³⁺). However, individual pro