title: Density functional theory calculations on the Fe2S2(Arg)(SCys)(SSCys)2 cluster in HydE: unique electronic structure and redox properties.
abstract: A Fe2S2 cluster with unprecedented CysSS(-) (cysteinepersulfide) coordination has been observed crystallographically in the AdoMet-dependent hydrogenase maturase enzyme HydE. Geometry-optimized density functional theory calculations are used to develop an electronic structure description of this unusual cluster. The results indicate that the CysSS(-) ligand is unique because it can act as a donor as well as an acceptor ligand. This is due to the presence of S-S π* (occupied) and S-S σ* (unoccupied) orbitals in this ligand. Extensive back-bonding is observed between the cluster and the S-S σ* orbital. The back-bonding is significantly higher in the reduced state, which is calculated to shift the reduction potential of this Fe2S2 cluster by +400 mV in the gas phase relative to a CysS(-)-coordinated Fe2S2 cluster model of BioB.
authors.affiliation: Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata, India 700032.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Dey
mesh_terms: D001665:Binding Sites; D003545:Cysteine / Q000737:chemistry; D004583:Electrons; D005296:Ferrous Compounds / Q000737:chemistry*; D007202:Indicators and Reagents; D008024:Ligands; D008667:Metalloproteins / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction
chemical_list: D005296:Ferrous Compounds; D007202:Indicators and Reagents; D008024:Ligands; D008667:Metalloproteins; D003545:Cysteine; C022597:ferrous sulfide