Pitfalls in assigning heme axial coordination by EPR. c-Type cytochromes with atypical Met-His ligation.
Different monohemic c-type cytochromes were analyzed by visible, EPR and 1H NMR spectroscopies. While the visible and NMR data show unambiguously that the heme iron has a Met-His heme axial coordination, the EPR data indicate an axial ligand field typical of that for a bis-histidinyl ligation. The validity of the widely used EPR methods for the determination of the heme iron axial coordination, based on the crystal field parameters (tetragonality and rhombicity), is questioned.
Centro de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal.
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D001426:Bacterial Proteins / Q000737:chemistry; D003574:Cytochrome c Group / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000737:chemistry*; D006639:Histidine; D009682:Magnetic Resonance Spectroscopy; D008715:Methionine; D013057:Spectrum Analysis
D001426:Bacterial Proteins; D003574:Cytochrome c Group; D006418:Heme; D006639:Histidine; D008715:Methionine