A novel conformer of oxidized Paracoccus pantotrophus cytochrome cd(1) observed by freeze-quench NIR-MCD spectroscopy.
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.
Allen
J W
JW
Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, United Kingdom.
Cheesman
M R
MR
Higham
C W
CW
Ferguson
S J
SJ
Watmough
N J
NJ
D003574:Cytochrome c Group; D003580:Cytochromes / Q000737:chemistry* / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005615:Freezing; D009572:Nitrite Reductases / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D010230:Paracoccus / Q000201:enzymology*; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared / Q000379:methods
D003574:Cytochrome c Group; D003580:Cytochromes; C019315:cytochrome cd1; D009572:Nitrite Reductases