A strongly bound high-spin iron(II) coordinates cysteine and homocysteine in cysteine dioxygenase
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Updated: May 27, 2026
Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR
Published on: December 16, 2013
Egor P Tchesnokov1, Sigurd M Wilbanks, Guy N L Jameson
1Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, Dunedin 9054, New Zealand.
Abstract:
The first experimental evidence of a tight binding iron(II)-CDO complex is presented. These data enabled the relationship between iron bound and activity to be explicitly proven. Cysteine dioxygenase (CDO) from Rattus norvegicus has been expressed and purified with ~0.17 Fe/polypeptide chain. Following addition of exogenous iron, iron determination using the ferrozine assay supported a very tight stoichiometric binding of iron with an extremely slow rate of dissociation, k(off) ~ 1.7 × 10(-6) s(-1). Dioxygenase activity was directly proportional to the concentration of iron. A rate of cysteine binding to iron(III)-CDO was also measured. Mössbauer spectra show that in its resting state CDO binds the iron as high-spin iron(II). This iron(II) active site binds cysteine with a dissociation constant of ~10 mM but is also able to bind homocysteine, which has previously been shown to inhibit the enzyme.
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