title: Combining spectroscopy and theory to evaluate structural models of metalloenzymes: a case study on the soluble [NiFe] hydrogenase from Ralstonia eutropha.
abstract: Hydrogenases catalyse the reversible cleavage of molecular hydrogen into protons and electrons. While most of these enzymes are inhibited under aerobic conditions, some hydrogenases are catalytically active even at ambient oxygen levels. In particular, the soluble [NiFe] hydrogenase from Ralstonia eutropha H16 couples reversible hydrogen cycling to the redox conversion of NAD(H). Its insensitivity towards oxygen has been formerly ascribed to the putative presence of additional cyanide ligands at the active site, which has been, however, discussed controversially. Based on quantum chemical calculations of model compounds, we demonstrate that spectroscopic consequences of the proposed non-standard set of inorganic ligands are in contradiction to the underlying experimental findings. In this way, the previous model for structure and function of this soluble hydrogenase is disproved on a fundamental level, thereby highlighting the efficiency of computational methods for the evaluation of experimentally derived mechanistic proposals.
authors.affiliation: Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 135, 10623 Berlin, Germany. marius.horch@gmx.de
authors.forename: Marius
authors.initials: M
authors.lastname: Horch
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Rippers
authors.forename: Maria A
authors.initials: MA
authors.lastname: Mroginski
authors.forename: Peter
authors.initials: P
authors.lastname: Hildebrandt
authors.forename: Ingo
authors.initials: I
authors.lastname: Zebger
mesh_terms: D001665:Binding Sites; D020118:Cupriavidus necator / Q000201:enzymology*; D006864:Hydrogenase / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011487:Protein Conformation; D012995:Solubility; D013055:Spectrophotometry, Infrared; D013379:Substrate Specificity
chemical_list: D008024:Ligands; C043296:nickel-iron hydrogenase; D006864:Hydrogenase; D010100:Oxygen