Cm. Gomes et al., STUDIES ON THE REDOX CENTERS OF THE TERMINAL OXIDASE FROM DESULFOVIBRIO-GIGAS AND EVIDENCE FOR ITS INTERACTION WITH RUBREDOXIN, The Journal of biological chemistry, 272(36), 1997, pp. 22502-22508
Rubredoxin-oxygen oxidoreductase (ROO) is the final component of a sol
uble electron transfer chain that couples NADH oxidation to oxygen con
sumption in the anaerobic sulfate reducer Desulfovibrio gigas. It is a
n 86-kDa homodimeric flavohemeprotein containing two FAD molecules, on
e mesoheme IX, and one Fe-uroporphyrin I per monomer, capable of fully
reducing oxygen to water. EPR studies on the native enzyme reveal two
components with g values at similar to 2.46, 2.29, and 1.89, which ar
e assigned to low spin hemes and are similar to the EPR features of P-
450 hemes, suggesting that ROO hemes have a cysteinyl axial ligation.
At pH 7.6, the flavin redox transitions occur at 0 +/- 15 mV for the q
uinone/semiquinone couple and at -130 +/- 15 mV for the semiquinone/hy
droquinone couple; the hemes reduction potential is -350 +/- 15 mV. Sp
ectroscopic studies provided unequivocal evidence that the flavins are
the electron acceptor centers from rubredoxin, and that their reducti
on proceed through an anionic semiquinone radical. The reaction with o
xygen occurs in the flavin moiety. These data are strongly corroborate
d by the finding that rubredoxin and ROO are located in the same polyc
istronic unit of D. gigas genome. For the first time, a clear role for
a rubredoxin in a sulfate-reducing bacterium is presented.