Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

J Phys Chem B. 2019 Sep 19;123(37):7785-7793. doi: 10.1021/acs.jpcb.9b05866. Epub 2019 Sep 6.

Abstract

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an in situ structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semiempirical computational methods, demonstrating that the Fe(III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and +171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox-difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Binding Sites
  • Iron Compounds / chemistry
  • Iron Compounds / metabolism
  • Ketoglutaric Acids / chemistry
  • Ketoglutaric Acids / metabolism
  • Mixed Function Oxygenases / chemistry
  • Mixed Function Oxygenases / metabolism*
  • Molecular Conformation
  • Oxidation-Reduction

Substances

  • Iron Compounds
  • Ketoglutaric Acids
  • Mixed Function Oxygenases
  • taurine-alpha-ketoglutarate dioxygenase