| Abstrakt: |
An EPR redox titration was performed on the tetraheme cytochrome cs 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 gmax = 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., Mourn, I., LeGall, J. & Xavier, A. V. (1984) Eur. J. Biochem. 141, 283-296] is discussed in terms of the EPR results. [ABSTRACT FROM AUTHOR] |
