Gf. Azzone et al., THE EFFECT OF THE PROTONMOTIVE FORCE ON THE REDOX STATE OF MITOCHONDRIAL CYTOCHROMES, Biochimica et biophysica acta. Bioenergetics, 1187(2), 1994, pp. 140-144
In the absence of kinetic limitations, as determined either by high su
bstrate concentrations or by absence of respiratory chain inhibitors,
we have observed that: (a) the relationship between the percentage red
uction of the cytochromes and the protonmotive force is linear in the
case of cytochrome c and biphasic in the case of cytochrome b, (b) the
redox state of cytochrome c depends only on the membrane potential an
d not on the total proton motive force and (c) the alkalinization of t
he matrix enhances the extent of cytochrome c reduction because of the
marked inhibitory effect on the cytochrome oxidase activity. Thus, al
though the redox states of the b, c and aa(3) mitochondrial cytochrome
s depend on the protonmotive force, the quantitative correlation betwe
en the two parameters and the relative effects of the electrical and c
hemical components of the force differ among the various cytochromes.