Assignment of individual heme EPR signals of Desulfovibrio baculatus (strain 9974) tetraheme cytochrome c3. A redox equilibria study.
An EPR redox titration was performed on the tetraheme cytochrome c3 isolated from Desulfovibrio baculatus (strain 9974), a sulfate-reducer. Using spectral differences at different poised redox states of the protein, it was possible to individualize the EPR g-values of each of the four hemes and also to determine the mid-point redox potentials of each individual heme: heme 4 (-70 mV) at gmax = 2.93, gmed = 2.26 and gmin = 1.51; heme 3 (-280 mV) at gmax = 3.41; heme 2 (-300 mV) at gmax = 3.05, gmed = 2.24 and gmin = 1.34; and heme 1 (-355 mV) at gmx = 3.18. A previously described multi-redox equilibria model used for the interpretation of NMR data of D. gigas cytochrome c3 [Santos, H., Moura, J.J.G., Moura, I., LeGall, J. & Xavier, A. V. (1984) Eur. J. Biochem. 141, 283-296] is discussed in terms of the EPR results.
Moura
I
I
Centro de Quimica Estrutural Complexo I, UNL, Lisboa, Portugal.
Teixeira
M
M
Huynh
B H
BH
LeGall
J
J
Moura
J J
JJ
D003574:Cytochrome c Group / Q000378:metabolism*; D003901:Desulfovibrio / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000378:metabolism*; D010084:Oxidation-Reduction
D003574:Cytochrome c Group; D006418:Heme; C017165:cytochrome c(3)