SCAN:Molecular details of electron transfer in fumarate reduction by flavocytochrome c3

ITQB Scan Seminar

Title: Molecular details of electron transfer in fumarate reduction by
flavocytochrome c3

Speaker: Catarina Paquete

From: Post-Doc at Inorganic Biochemistry and NMR Laboratory

Abstract:

Numerous redox enzymes catalyze two-electron processes, even though the
connection from the protein surface to the active site is made through
chains of redox cofactors that only exchange one electron at a time. The
soluble fumarate reductase from the periplasmic space of Shewanella is one
of these proteins. The three-dimensional structure showed that this
protein contains a chain of four hemes, which interacts with the FAD
catalytic centre that performs the obligatory two electron-two proton
reduction of fumarate to succinate. In order to investigate the role
played by the redox chain in the catalytic activity of this enzyme,
transient kinetic studies of flavocytochrome reduction in the absence and
in the presence of substrate were performed. The kinetic contribution of
each heme for electron uptake and conduction to the catalytic centre was
determined. This enabled the observation that the catalytically most
competent states of the enzyme are those least prevalent in a
quasi-stationary condition of turnover. Finally, the molecular details of
electron transfer within these enzymes during turnover suggested a role in
the switch between respiration of solid and soluble terminal electron
acceptors in the anaerobic bioenergetic metabolism of Shewanella.