Cytochrome BC1 Complex - Coenzyme Q : Cytochrome C-Oxidoreductase
Family:
Oxidoreductases
Structure:
In vertebrates, Cytochrome bc1 complex is a multisubunit transmembrane protein encoded by both the mitochondrial (cytochrome b) and the nuclear genomes (all other subunits). The bc1 complex contains 11 subunits, 3 respiratory subunits (cytochrome B, cytochrome C1, Rieske protein), 2 core proteins and 6 low-molecular weight proteins.
Function:
The cytochrome bc1 complex contributes to the proton gradient by an asymmetric absorption/release of protons (electron transfer chain (ETC) complex III). Complex III is present in the mitochondria of all animals and all aerobic eukaryotes and the inner membranes of most eubacteria.
It catalyzes the reduction of cytochrome c by oxidation of coenzyme Q (CoQ) and the concomitant pumping of 4 protons from the mitochondrial matrix to the intermembrane space:
QH2 + 2 cytochrome c (FeIII) + 2 H+in → Q + 2 cytochrome c (FeII) + 4 H+out
In the process called Q cycle, two protons are consumed from the matrix (M), four protons are released into the inter membrane space (IM) and two electrons are passed to cytochrome c.
Data and Applications
Respiratory Chain Complex II and III - Current Traces
SURFE2R N1 data and applications:
Respiratory Chain Complex II is a succinate dehydrogenase. In this complex, succinate is oxidated to fumarate. The electrons are transfered to the quinone pool, the Complex III (cytochrome bc1 complex) and cytochrome c, while four protons are transported to the intermembrane space.
Respiratory Chain Complex I and III - Current Over Mitochondrial Membrane
SURFE2R N1 data and applications:
In the respiratory chain Complex I and III, oxidation of NADH leads to transport of 4 protons across the membrane. The electrons are transferred to cytochrome c. Because of the electron leakage to oxygen, both complex are the main sites of production of harmful superoxide. In these experiments using the SURFE2R N1, application of 100µM NADH results in a current over the mitochondrial membrane, where Complex I and III are expressed.
Publications
2013 - Measuring Interference of Drug-Like Molecules with the Respiratory Chain: Toward the Early Identification of Mitochondrial Uncouplers in Lead Finding
SURFE²R N96 (predecessor model of SURFE²R 96SE) publication in Assay and Drug Development Technologies (2013)
Authors:
Stock U., Matter H., Diekert K., Dörner W., Dröse S., Licher T.
2011 - Development of an assay for Complex I/Complex III of the respiratory chain using solid supported membranes and its application in mitochondrial toxicity screening in drug discovery
SURFE²R ONE (a predecessor model of SURFE²R N1) publication in ASSAY and Drug Development Technologies (2011)
Authors:
Preissl S., Bick I., Obrdlik P., Diekert K., Gul S., Gribbon P.
2010 - Electrophysiology of respiratory chain complexes and the ADP-ATP exchanger in native mitochondrial membranes
SURFE²R ONE (a predecessor model of SURFE²R N1) publication in Biochemistry (2010)
Authors:
Watzke N., Diekert K., Obrdlik P.
a. P-bond hydrolysis driven transporters