Fig. 6
From: Crystallographic and spectroscopic assignment of the proton transfer pathway in [FeFe]-hydrogenases
Influence of SDM on the proton transfer mechanism during H2-uptake in CpI. Effects of SDM on the proposed proton transfer mechanism for selected CpI variants: C299A (a), E279A (b), E282A (c), and E282Q (d). H2-binding induces a shift in the H-bond pattern (from mode 1 to mode 2) and initiates the catalytic mechanism during which the H-bond pattern repeatedly shifts between modes 1 (blue) and 2 (green) while promoting a stepwise proton release via the PT pathway (for details see Supplementary Fig. 9+14). The pKa values of adt-ligand at different redox states are derived from previous studies49,58. The mutated residues and hydrogen atoms from substrate were highlighted as red. The green double arrow indicates a putative salt bridge contact. In c (E282A), the pink shading area indicates a slowed-down but still functioning proton transfer. Protons presented in blue close to the [4Fe]H sub-cluster originate from the recently described regulatory PT pathway34,59,60, which is independent of substrate/product transfer
