Fig. 1.
Schematic representation for electron and proton supply channels in the form of [FeS]-relay ET and PT pathways, respectively, based on the structure of CpI. As is shown in this paper, in WT enzyme both ET and PT pathways are strongly coupled, thus ensuring reversible catalysis at the H-cluster (A). If the PTP is impeded (B), ET is also impeded as PT is uncoupled from ET at the H-cluster. (C) Close-up of the PT pathway for CpI WT and exchange variants E282DCpI and E279DCpI (PDB ID codes 4XDC, 6GM2, and 6YF4, respectively). The H-bonding networks are represented by dashed lines and distances are indicated in angstroms. Color code for atoms: gray/black: carbon; red: oxygen; blue: nitrogen; yellow: sulfur; orange: iron.