Resonance Raman spectroscopic identification of a histidine ligand of b(sub 595) and the nature of the ligation of chlorin d in the fully reduced Escherichia coli cytochrome bd oxidase

The resonance Raman (rR) spectral analysis indicates that the ligand close to high spin heme (b(sub 595)) of cytochrome bd oxidase is histidine 19. The rR frequencies of ferrous low spin heme (b(sub 558)) correlate with a His/Met axial ligation. EPR analysis indicates that binding of the oxidized chlorin d to CN- generates high-spin chlorin motifs. The chlorin d cofactor in reduced cytochrome bd oxidase exists in a 5-coordinate high-spin state. The administration of cyanide to the fully reduced enzyme has no influence on the structures of b(sub 558) and b(sub 559).