Reaction of cyanide with cytochrome ba3 from Thermus thermophilus: Spectroscopic characterization of the Fe(II)a3-CN·Cu(II)B-CN complex suggests four 14N atoms are coordinated to CUB

Kristene K. Surerus, W. Anthony Oertling, Chaoliang Fan, Ryszard J. Gurbiel, Ólöf Einarsdóttir, William E. Antholine, R. Brian Dyer, Brian M. Hoffman, William H. Woodruff, James A. Fee*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


Cytochrome ba3 from Thermus thermophilus reacts slowly with excess HCN at pH 7.4 to create a form of the enzyme in which CuA, cytochrome b, and CUB remain oxidized, while cytochrome a3 is reduced by one electron, presumably with the formation of cyanogen. We have examined this form of the enzyme by UV-visible, resonance Raman, EPR, and electron nuclear double resonance spectroscopies in conjunction with permutations of 13C- and 15N-labeled cyanide. The results support a model in which one CN- binds through the carbon atom to ferrous a3, supporting a low-spin (S = 0) configuration on the Fe; bridging by this cyanide to the CUB is weak or absent. Four 14N atoms, presumably donated by histidine residues of the protein, provide a strong equatorial ligand field about CuB; a second CN- is coordinated through the carbon atom to CuB in an axial position.

Original languageEnglish (US)
Pages (from-to)3195-3199
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number8
StatePublished - 1992


  • Cyanide complex

ASJC Scopus subject areas

  • General

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