Difference between revisions of "Electron transfer pathway"
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== Electron transfer system versus chain == | == Electron transfer system versus chain == | ||
The term '''electron transport chain''' (or electron transfer chain, ETC) is a misnomer. Understanding mitochondrial respiratory control has suffered greatly from this inappropriate terminology, although textbooks using the term ETC (Lehninger 1970) make it sufficiently clear that '''electron transfer systems are not arranged as a chain''': the „ETC‟ is in fact not a simple chain but an arrangement of electron transfer complexes in a non-linear, convergent electron transfer system. The classically introduced term '''electron transfer system''' (Hatefi et al 1962<ref>Hatefi Y, Haavik AG, Fowler LR, Griffiths DE (1962) Studies on the '''electron transfer system''' XLII. Reconstitution of the electron transfer system. J Biol Chem 237: 2661-2669. [[Hatefi 1962 J Biol Chem-XLII | | The term '''electron transport chain''' (or electron transfer chain, ETC) is a misnomer. Understanding mitochondrial respiratory control has suffered greatly from this inappropriate terminology, although textbooks using the term ETC (Lehninger 1970) make it sufficiently clear that '''electron transfer systems are not arranged as a chain''': the „ETC‟ is in fact not a simple chain but an arrangement of electron transfer complexes in a non-linear, convergent electron transfer system. The classically introduced term '''electron transfer system''' (Hatefi et al 1962 <ref> Hatefi Y, Haavik AG, Fowler LR, Griffiths DE (1962) Studies on the '''electron transfer system''' XLII. Reconstitution of the electron transfer system. J Biol Chem 237: 2661-2669. [[Hatefi 1962 J Biol Chem-XLII |»Open Access]]</ref>) is accurate and sufficient. <ref> International Union of Biochemistry (1991) Nomenclature of '''electron-transfer proteins.''' Biochim Biophys Acta 1060. [http://www.chem.qmul.ac.uk/iubmb/etp/ »Open Access]</ref> | ||
<ref> | |||
The established convention of defining the 'electron transport chain' as being comprised of four Complexes has conceptual weaknesses. | The established convention of defining the 'electron transport chain' as being comprised of four Complexes has conceptual weaknesses. | ||
(a) In fact, there are at least six Complexes of mitochondrial electron transfer: In addition to Complexes I and II, [[Glycerophosphate_dehydrogenase|glycerophosphate dehydrogenase]] (GpDH) and [[Electron-transferring_flavoprotein|electron transferring flavoprotein]] (ETF) are involved in the [[Q-junction]] with electron transfer to [[Complex III]]. | (a) In fact, there are at least six Complexes of mitochondrial electron transfer: In addition to Complexes I and II, [[Glycerophosphate_dehydrogenase|glycerophosphate dehydrogenase]] (GpDH) and [[Electron-transferring_flavoprotein|electron transferring flavoprotein]] (ETF) are involved in the [[Q-junction]] with electron transfer to [[Complex III]]. | ||
<ref> | <ref>International Union of Biochemistry (1991) Nomenclature of '''electron-transfer proteins.''' Biochim Biophys Acta 1060. [http://www.chem.qmul.ac.uk/iubmb/etp/ »Open Access]</ref>,<ref>Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. [[Gnaiger_2012_MitoPathways |»Open Access]]</ref> | ||
(b) The term „chain‟ suggests a linear sequence, whereas the functional structure of the electron transfer system can only be understood by recognizing '''the convergence of electron flow at the Q-junction''', followed by a chain of Complexes III and IV, mediated by [[cytochrome c | cytochrome ''c'']].<ref>Gnaiger E (2012) Mitochondrial | (b) The term „chain‟ suggests a linear sequence, whereas the functional structure of the electron transfer system can only be understood by recognizing '''the convergence of electron flow at the Q-junction''', followed by a chain of Complexes III and IV, mediated by [[cytochrome c | cytochrome ''c'']]. <ref> Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. [[Gnaiger_2012_MitoPathways |»Open Access]]</ref> | ||
Electrons flow to oxygen from either [[Complex I]] with a total of three coupling sites, or from [[Complex II]] and other flavoproteins, providing multiple entries into the Q-cycle with two coupling sites downstream.<ref>Gnaiger E (2012) Mitochondrial | Electrons flow to oxygen from either [[Complex I]] with a total of three coupling sites, or from [[Complex II]] and other flavoproteins, providing multiple entries into the Q-cycle with two coupling sites downstream. <ref> Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. [[Gnaiger_2012_MitoPathways |»Open Access]]</ref> | ||
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(ii) '''Transport''' (from one place to another) of an entity is a (vectorial) process in contrast to a chemical reaction. | (ii) '''Transport''' (from one place to another) of an entity is a (vectorial) process in contrast to a chemical reaction. | ||
<ref>International Union of Biochemistry and Molecular Biology. Recommendations for terminology and databases for biochemical thermodynamics - The IUPAC Green Book [http://www.chem.qmul.ac.uk/iubmb/thermod2/ | <ref> International Union of Biochemistry and Molecular Biology. Recommendations for terminology and databases for biochemical thermodynamics - The IUPAC Green Book [http://www.chem.qmul.ac.uk/iubmb/thermod2/ »Open Access].</ref> | ||
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=== The ETS state === | === The ETS state === | ||
* [[ETS capacity]]<ref>Gnaiger E. Why not State 3u? Mitochondr Physiol Network. | * [[ETS capacity]] - [[State 3u]]<ref>Gnaiger E. Why not State 3u? Mitochondr Physiol Network. »[[ETS capacity]]</ref> | ||
* [[ETS-competent substrate state]] | * [[ETS-competent substrate state]] | ||
* [[Level flow]] | * [[Level flow]] | ||
* [[Noncoupled respiration]] - [[Uncoupler]]<ref>Gnaiger E. Is respiration uncoupled - noncoupled - dyscoupled? Mitochondr Physiol Network. | * [[Noncoupled respiration]] - [[Uncoupler]]<ref>Gnaiger E. Is respiration uncoupled - noncoupled - dyscoupled? Mitochondr Physiol Network. »[[Uncoupler]]</ref> | ||
* [[Phosphorylation control protocol]] | * [[Phosphorylation control protocol]] | ||
=== ETS-related flux control factors === | === ETS-related flux control factors === | ||
* [[Biochemical coupling efficiency]]<ref>Gnaiger E. Biochemical coupling efficiency: from 0 to <1. Mitochondr Physiol Network. | * [[Biochemical coupling efficiency]]<ref>Gnaiger E. Biochemical coupling efficiency: from 0 to <1. Mitochondr Physiol Network. »[[Biochemical coupling efficiency]]</ref> | ||
* [[E-L coupling control factor]] - [[E-P coupling control factor]] - [[E-R coupling control factor]] | * [[E-L coupling control factor]] - [[E-P coupling control factor]] - [[E-R coupling control factor]] | ||
Revision as of 19:43, 21 April 2014
- high-resolution terminology - matching measurements at high-resolution
Electron transfer pathway
Description
The mitochondrial electron transfer system (ETS; synonymous with 'electron transport system') transfers electrons from externally supplied reduced substrates to oxygen. It consists of the membrane-bound ETS (mETS) with enzyme complexes located in the inner mt-membrane, mt-matrix dehydrogenases generating NADH, and the transport systems involved in metabolite exchange across the mt-membranes (see ETS capacity). > MiPNet article
Abbreviation: ETS
Reference: Gnaiger 2009 Int J Biochem Cell Biol
MitoPedia methods:
Respirometry
MitoPedia topics: "Respiratory state" is not in the list (Enzyme, Medium, Inhibitor, Substrate and metabolite, Uncoupler, Sample preparation, Permeabilization agent, EAGLE, MitoGlobal Organizations, MitoGlobal Centres, ...) of allowed values for the "MitoPedia topic" property.
Respiratory state"Respiratory state" is not in the list (Enzyme, Medium, Inhibitor, Substrate and metabolite, Uncoupler, Sample preparation, Permeabilization agent, EAGLE, MitoGlobal Organizations, MitoGlobal Centres, ...) of allowed values for the "MitoPedia topic" property.
| Gnaiger E (2013) Electron transfer system versus electron transport chain. Mitochondr Physiol Network 2013-08-18. |
OROBOROS (2013) Mitochondr Physiol Network
Abstract: The well established terms 'respiratory chain' or 'electron transfer chain' suggest erroneously that the convergent electron transfer system may be designed as a simple chain.
• O2k-Network Lab: AT Innsbruck Gnaiger E
Labels:
Coupling state: ETS"ETS" is not in the list (LEAK, ROUTINE, OXPHOS, ET) of allowed values for the "Coupling states" property.
HRR: Theory
Electron transfer system versus electron transport chain
Electron transfer system versus chain
The term electron transport chain (or electron transfer chain, ETC) is a misnomer. Understanding mitochondrial respiratory control has suffered greatly from this inappropriate terminology, although textbooks using the term ETC (Lehninger 1970) make it sufficiently clear that electron transfer systems are not arranged as a chain: the „ETC‟ is in fact not a simple chain but an arrangement of electron transfer complexes in a non-linear, convergent electron transfer system. The classically introduced term electron transfer system (Hatefi et al 1962 [1]) is accurate and sufficient. [2]
The established convention of defining the 'electron transport chain' as being comprised of four Complexes has conceptual weaknesses.
(a) In fact, there are at least six Complexes of mitochondrial electron transfer: In addition to Complexes I and II, glycerophosphate dehydrogenase (GpDH) and electron transferring flavoprotein (ETF) are involved in the Q-junction with electron transfer to Complex III. [3],[4]
(b) The term „chain‟ suggests a linear sequence, whereas the functional structure of the electron transfer system can only be understood by recognizing the convergence of electron flow at the Q-junction, followed by a chain of Complexes III and IV, mediated by cytochrome c. [5]
Electrons flow to oxygen from either Complex I with a total of three coupling sites, or from Complex II and other flavoproteins, providing multiple entries into the Q-cycle with two coupling sites downstream. [6]
Electron transfer versus transport
Electron transfer and electron transport are used synonymously. A general distinction, however, may be helpful:
(i) Transfer (inter- or intramolecular) of a reactant involves a chemical reaction.
(ii) Transport (from one place to another) of an entity is a (vectorial) process in contrast to a chemical reaction. [7]
Related terms in MitoPedia
The ETS state
- ETS capacity - State 3u[8]
- ETS-competent substrate state
- Level flow
- Noncoupled respiration - Uncoupler[9]
- Phosphorylation control protocol
- Biochemical coupling efficiency[10]
- E-L coupling control factor - E-P coupling control factor - E-R coupling control factor
- Coupling control ratio - Uncoupling control ratio
- LEAK control ratio per E - Phosphorylation system control ratio
- ROUTINE control ratio - NetROUTINE control ratio
References
- ↑ Hatefi Y, Haavik AG, Fowler LR, Griffiths DE (1962) Studies on the electron transfer system XLII. Reconstitution of the electron transfer system. J Biol Chem 237: 2661-2669. »Open Access
- ↑ International Union of Biochemistry (1991) Nomenclature of electron-transfer proteins. Biochim Biophys Acta 1060. »Open Access
- ↑ International Union of Biochemistry (1991) Nomenclature of electron-transfer proteins. Biochim Biophys Acta 1060. »Open Access
- ↑ Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. »Open Access
- ↑ Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. »Open Access
- ↑ Gnaiger E (2012) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 3rd ed. Mitochondr Physiol Network 17.18. OROBOROS MiPNet Publications, Innsbruck: 64 pp. »Open Access
- ↑ International Union of Biochemistry and Molecular Biology. Recommendations for terminology and databases for biochemical thermodynamics - The IUPAC Green Book »Open Access.
- ↑ Gnaiger E. Why not State 3u? Mitochondr Physiol Network. »ETS capacity
- ↑ Gnaiger E. Is respiration uncoupled - noncoupled - dyscoupled? Mitochondr Physiol Network. »Uncoupler
- ↑ Gnaiger E. Biochemical coupling efficiency: from 0 to <1. Mitochondr Physiol Network. »Biochemical coupling efficiency
