A novel conformer of oxidized Paracoccus pantotrophus cytochrome cd(1) observed by freeze-quench NIR-MCD spectroscopy

James W. A. Allen, Myles R. Cheesman, Christopher W. Higham, Stuart J. Ferguson, Nicholas J. Watmough

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14 Citations (Scopus)


Paracoccus pantotrophus cytochrome cd(1) is a physiological nitrite reductase and an in vitro hydroxylamine reductase. The oxidised "as isolated" form of the enzyme has bis-histidinyl coordinated c-heme and upon reduction its coordination changes to histidine/ methionine. Following treatment of reduced enzyme with hydroxylamine, a novel, oxidised, conformer of the enzyme is obtained. We have devised protocols for freeze-quench near-ir-MCD spectroscopy that have allowed us to establish unequivocally the c-heme coordination of this species as His/Met. Thus it is shown that the catalytically competent, hydroxylamine reoxidised, form of P. pantotrophus cytochrome cd(1) has different axial ligands to the c-heme than "as isolated" enzyme. (C) 2000 Academic Press.
Original languageEnglish
Pages (from-to)674-677
Number of pages4
JournalBiochemical and Biophysical Research Communications
Issue number2
Publication statusPublished - 2000

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