title: A strongly bound high-spin iron(II) coordinates cysteine and homocysteine in cysteine dioxygenase.
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.
authors: Department of Chemistry & MacDiarmid Institute for Advanced Materials and Nanotechnology, University of Otago, Dunedin 9054, New Zealand.
authors: Egor P
authors: EP
authors: Tchesnokov
authors: Sigurd M
authors: SM
authors: Wilbanks
authors: Guy N L
authors: GN
authors: Jameson
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D003545:Cysteine / Q000737:chemistry* / Q000378:metabolism; D050558:Cysteine Dioxygenase / Q000737:chemistry* / Q000378:metabolism; D005296:Ferrous Compounds / Q000737:chemistry* / Q000378:metabolism; D006710:Homocysteine / Q000737:chemistry* / Q000378:metabolism; D033862:Iron-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D011485:Protein Binding; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015204:Spectroscopy, Mossbauer; D013997:Time Factors
chemical_list: D005296:Ferrous Compounds; D033862:Iron-Binding Proteins; D008024:Ligands; D011994:Recombinant Proteins; D006710:Homocysteine; D050558:Cysteine Dioxygenase; D003545:Cysteine