Description
Cytochrome c is a component of the electron transfer system (ETS) in mitochondria. It is a small heme protein loosely associated with the outer side of the inner mitochondrial membrane. The heme group of cytochrome c transfers electrons from Complex III to Complex IV. The release of cytochrome c into the cytoplasm is associated with apoptosis. > MiPNet article
Abbreviation: c
Reference: MiPNet09.12; Gnaiger 2002 Biochem Soc Trans
MitoPedia topics: Substrate and metabolite
Application in HRR: storage and stock solution of c
c: Cytochrome c (from equine heart), Sigma C 7752, 50 mg, store at -20 Β°C; FW = 12500.
Preparation of 4 mM cytochrome c solution (dissolved in H2O):
- 1. Weigh 50 mg cytochrome c into a small glass beaker. Difficult to weigh, since the powder is electromagnetic.
- 2. Add 1 ml H2O; c dissolves easily.
- 3. Divide into 0.2 ml portions.
- 4. Store at -20 Β°C.
Caution: Chemicals stored in the fridge or freezer should be allowed to reach room temperature before opening.
Oxygraph-2k manual titrations: MiPNet09.12 O2k-Titrations
- Titration volume: 5 Β΅l using a 25 Β΅l syringe (2 ml O2k-chamber)
- Final concwentration: 10 Β΅M
Gnaiger E (2014) Cytochrome c control: a test for outer mt-membrane integrity. Mitochondr Physiol Network 2014-04-21. |
OROBOROS (2014) Mitochondr Physiol Network
Abstract: The cytochrome c control factor, (JCHOc-JCHO)/JCHOc, provides an index for the outer mt-membrane integrity.
β’ O2k-Network Lab: AT Innsbruck Gnaiger E
Labels:
HRR: Theory
Cytochrome c control: a test for outer mt-membrane integrity
Outer mitochondrial membrane damage can be evaluated by stimulation of respiration by exogenously added cytochrome c.
Determination of cytochrome c loss
Adding cytochrome c (10 Β΅M)[1] to stimulate respiratory activity provides an estimate of cytochrome c loss. In general, maximum respiratory activity is obtained under conditions of saturating substrate concentrations and system dependent in the coupled (ADP stimulated) State P or noncoupled (uncoupler stimulated) State E.
Cytochrome c test
When using cytochrome c as a quality control for permeabilised muscles from various species, which cytochrome c should we use (a wide range of types of cytochrome c is available from Sigma-Aldrich) and at which concentration?
We apply routinely cytochrome c from Sigma C 7752.[2] It would be interesting to compare the consequence of application of different sources of cytochrome c.
In a detailed discussion on the dependence of respiration in isolated mitochondria and permeabilized cardiac fibers, we showed for the first time showing that cytochrome c kinetics is different when studying a segment of the ETS (CII-linked: succinate+rotenone) versus the isolated step of cytochrome c oxidase (CIV; ascorbate+TMPD+antimycin A). For CII-linked respiration, an exernal cytochrome c concentration of 10 Β΅M yields kinetic saturation (monophasic hyperbolic), but kinetics is biphasic for CIV and 10 Β΅M is not saturating.[3],[4]
Importantly, cytochrome c increases the chemical background oxygen flux in the presence of ascorbate and TMPD, dependent on oxygen concentration and cytochrome c concentration, and appropriate chemical background corrections are required.[5],[6] Without ascorbate and TMPD, added cytochrome c is stable.
Evaluation of the cytochrome c effect, when respiration is slightly unstable: Mark respiration just before cytochrome c addition and after. Take these to values to calculate the increase of respiration due to cytochrome c addition.
At which step of the protocol should cytochrome c be added?
If a stimulatory effect of cytochrome c is observed, respiratory capacities measured before cytochrome c addition might be cytochrome c limited and therefore underestimated. This provides an argument to add cytochrome c at an early state of the protocol.
It is important not to add cytochrome c in a LEAK state: There is always an unexplained activation of respiration, unrelated to the injury of the outer mt-membrane. Add cytochrome c only after activation by ADP.
Cytochrome c release
Cytochrome c release induced by sample preparation
A preparation induced damage of the outer mitochondrial membrane and as a result subsequent loss of cytochrome c can be detected by a stimulation of respiration after the addition of cytochrome c. The preparation induced damage can also affect the respiratory complexes. Therefore, experimental runs showing a preparation induced cytochrome c release should be excluded from the final data set. In perfectly prepared muscle fibers cytochrome c should have no stimulatory effect on maximum respiratory activity, in liver biopsies a small effect is observed, even in carefully prepared samples.
Cytochrome c release induced by treatment
Treatment-triggered cytochrome c release, e.g. cell death induction, has to be distinguished from preparation induced damage. If cytochrome c is released as a result of apoptosis induction, this is a biological phenomenon and a relevant result.
References
- β Kuznetsov AV, Schneeberger S, Seiler R, Brandacher G, Mark W, Steurer W, Saks V, Usson Y, Margreiter R, Gnaiger E (2004) Mitochondrial defects and heterogeneous cytochrome c release after cardiac cold ischemia and reperfusion. Am J Physiol Heart Circ Physiol 286: H1633βH1641. >> Open Access
- β Fontana-Ayoub M, Fasching M, Gnaiger E (2014) Selected media and chemicals for respirometry with mitochondrial preparations. Mitochondr Physiol Network 03.02(17): 1-9. >> Open Access
- β Gnaiger E, Kuznetsov AV (2002) Mitochondrial respiration at low levels of oxygen and cytochrome c. Biochem Soc Trans 30: 242-248. >> PMID: 12023860
- β Kuznetsov AV, Schneeberger S, Seiler R, Brandacher G, Mark W, Steurer W, Saks V, Usson Y, Margreiter R, Gnaiger E (2004) Mitochondrial defects and heterogeneous cytochrome c release after cardiac cold ischemia and reperfusion. Am J Physiol Heart Circ Physiol 286: H1633βH1641. >> Open Access
- β Renner K, Amberger A, Konwalinka G, Kofler R, Gnaiger E (2003) Changes of mitochondrial respiration, mitochondrial content and cell size after induction of apoptosis in leukemia cells. Biochim Biophys Acta 1642: 115-123. >> PMID: 12972300
- β Kuznetsov AV, Gnaiger E (2010) Oxygraph assay of cytochrome c oxidase activity: chemical background correction. Mitochondr Physiol Network 06.06(07): 1-4. >> Open Access