Ligation and Reactivity of Methionine-Oxidized Cytochrome c
| Autor: | Fangfang Zhong, Ekaterina V. Pletneva |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Stereochemistry Iron Peptide Heme Ligands Spectrum Analysis Raman 010402 general chemistry Models Biological 01 natural sciences Article Ferrous Inorganic Chemistry 03 medical and health sciences chemistry.chemical_compound Methionine Yeasts Metalloprotein medicine Amino Acid Sequence Physical and Theoretical Chemistry chemistry.chemical_classification Binding Sites biology Ligand Cytochrome c Electron Spin Resonance Spectroscopy Imidazoles Cytochromes c Sulfoxide 0104 chemical sciences 030104 developmental biology chemistry Sulfoxides biology.protein Ferric Oxidation-Reduction medicine.drug |
| Zdroj: | Inorganic Chemistry. 57:5754-5766 |
| ISSN: | 1520-510X 0020-1669 |
| DOI: | 10.1021/acs.inorgchem.8b00010 |
| Popis: | Met80, one of the heme iron ligands in cytochrome c (cyt c) is readily oxidized to Met sulfoxide (Met-SO) by several biologically-relevant oxidants. The modification has been suggested to impact both the electron-transfer (ET) and apoptotic functions of this metalloprotein. The coordination of the heme iron in Met-oxidized cyt c (Met-SO cyt c) is critical for both of these functions but has remained poorly defined. We present electronic absorption, NMR, and EPR spectroscopic investigations as well kinetic studies and mutational analyses to identify the heme iron ligands in yeast iso-1 Met-SO cyt c. Similar to the alkaline form of native cyt c, Lys73 and Lys79 ligate to the ferric heme iron in the Met80-oxidized protein but this coordination takes place at much lower pH. The ferrous heme iron is ligated by Met-SO implying the redox-linked ligand switch in the modified protein. Binding studies with a model peptide microperoxidase-8 provide a rationale for alterations in ligation and for the role of the polypeptide packing in native and Met-SO cyt c. Imidazole binding experiments have revealed that Lys dissociation from the ferric heme in K73A/K79G/M80K (M80K#) and Met-SO is more than three orders of magnitude slower than the opening of the heme pocket that limits Met80 replacement in native cyt c. The Lys-to-Met-SO ligand substitution gates ET of ferric Met-SO cyt c with Co(terpy)22+. Owing to the slow Lys dissociation step, ET reaction is slow but possible, which is not the case for non-switchable M80A and M80K#. Acidic conditions cause Lys replacement by a water ligand in Met-SO cyt c (pKa=6.3±0.1) increasing intrinsic peroxidase activity of the protein. This pH-driven ligand switch may be a mechanism to boost peroxidase function of cyt c specifically in apoptotic cells. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|