Spectral properties of nitric oxide complexes of cytochrome c' from Alcaligenes sp. NCIB 11015

For the purpose of clarifying the stereochemistry of the heme environment and the electronic structure of the heme iron in cytochrome c' from Alcaligenes sp. NCIB 11015, the spectral properties of the nitric oxide ( super(14)NO and super(15)NO) derivatives of cytochrome c' have been investigated. The electronparamagnetic resonance (EPR) and electronic spectra vary with the change of pH either at room temperature or at 77 K. The results of EPR and electronic spectroscopies on NO-Alcaligenes cytochrome c' at physiological pH indicate that the heme iron to histidine (Fe-N sub( epsilon )) bond of cytochrome c' is very weak and is cleaved upon the coordination of a nitrosyl group. From a comparison of the electronic spectra for NO-cytochrome c' from various species, the decreasing order of the Fe-N sub( epsilon ) bond strength among species has been considered to be Rhodopseudomonas palustris) > Rhodospirillum rubrum > Alcaligenes .