The identification of histidine ligands to cytochrome a in cytochrome c oxidase.
A histidine auxotroph of Saccharomyces cerevisiae has been used to metabolically incorporate [1,3-15N2] histidine into yeast cytochrome c oxidase. Electron nuclear double resonance (ENDOR) spectroscopy of cytochrome a in the [15N]histidine-substituted enzyme reveals an ENDOR signal which can be assigned to hyperfine coupling of a histidine 15N 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 15N-substituted bisimidazole model compounds, metmyoglobin-[15N]imidazole and bis[15N]imidazole tetraphenyl porphyrin, provides strong evidence for bisimidazole coordination in cytochrome a.
Martin
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Scholes
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Chan
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D000818:Animals; D002417:Cattle; D017936:Cytochrome a Group; D003580:Cytochromes / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000032:analysis*; D006639:Histidine / Q000032:analysis*; D009206:Myocardium / Q000201:enzymology; D012441:Saccharomyces cerevisiae / Q000201:enzymology
D017936:Cytochrome a Group; D003580:Cytochromes; D006639:Histidine; D003576:Electron Transport Complex IV