The Identification of Histidine Ligands to Cytochrome
نویسنده
چکیده
A histidine auxotroph of Saccharomyces cerevieiae has been used to metabolically incorporate [1,3-'"N%] histidine into yeast cytochrome c oxidase. Electron nuclear double resonance (ENDOR) spectroscopy of cytochrome a in the ['6N]h~stidine-substituted enzyme reveals an ENDOR signal which can be assigned to hyperfine coupling of a histidine "N with the low-spin heme, thereby unambiguously identifying histidine as an axial ligand to this cytochrome. Comparison of this result with similar ENDOR data obtained on two '"Nsubstituted bisimidazole model compounds, metmy~globin-['~N]imidazole and bi~['~N]imidazole tetraphenyl porphyrin, provides strong evidence for bisimidazole coordination in cytochrome a.
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