Resonance Raman spectroscopy of Fe–S proteins and their redox properties

Resonance Raman spectra of Fe–S proteins are sensitive to the cluster type, structure and symmetry. Furthermore, bands that originate from bridging and terminal Fe–S vibrations in the 2Fe–2S, 3Fe–4S and 4Fe–4S clusters can be sensitively distinguished in the spectra, as well as the type of non-cysteinyl coordinating ligands, if present. For these reasons, resonance Raman spectroscopy has been playing an exceptionally active role in the studies of Fe–S proteins of diverse structures and functions. We provide here a concise overview of the structural information that can be obtained from resonance Raman spectroscopy on Fe–S clusters, and in parallel, refer to their thermodynamic properties (e.g., reduction potential), which together define the physiological roles of Fe–S proteins. We demonstrate how the knowledge gained over the past several decades on simple clusters nowadays enables studies of complex structures that include Fe–S clusters coupled to other centers and transient processes that involve cluster inter-conversion, biogenesis, disassembly and catalysis.