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.
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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