J. Biol. Chem., Vol. 261, Issue 1, 190-193, Jan, 1986
Complex formation and electron transfer between mitochondrial cytochrome c and flavocytochrome c552 from Chromatium vinosum
HR Bosshard, MW Davidson, DB Knaff and F Millett
Flavocytochrome c552 from Chromatium vinosum catalyzes the oxidation of
sulfide to sulfur using a soluble c-type cytochrome as an electron
acceptor. Mitochondrial cytochrome c forms a stable complex with
flavocytochrome c552 and may function as an alternative electron acceptor
in vitro. The recognition site for flavocytochrome c552 on equine
cytochrome c has been deduced by differential chemical modification of
cytochrome c in the presence and absence of flavocytochrome c552 and by
kinetic analysis of the sulfide:cytochrome c oxidoreductase activity of
m-trifluoromethylphenylcarbamoyl-lysine derivatives of cytochrome c. As
with mitochondrial redox partners, interaction occurs around the exposed
heme edge at the "front face" of cytochrome c. However, the domain
recognized by flavocytochrome c552 seems to extend to the right of the heme
edge, whereas the site of interaction with mitochondrial cytochrome c
oxidase and reductase is more to the left. Km but not Vmax of the electron
transfer reaction with mitochondrial cytochrome c increases with increasing
ionic strength. The correlation of chemical modification and ionic strength
dependence data indicates that the electrostatic interaction between the
two hemoproteins involves fewer ionic bonds than that with other redox
partners of cytochrome c.