Brandt 2013 Angew Chem Int Ed Engl

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Brandt U (2013) Inside view of a giant proton pump. Angew Chem Int Ed Engl 52:7358-60.

Β» PMID: 23703893

Brandt U (2013) Angew Chem Int Ed Engl

Abstract: Inner workings: The X-ray crystal structure of the entire bacterial complex I at 3.3 Γ… resolution offers fascinating insights into a giant 536 kDa molecular machine. The respiratory chain complex seems to employ unique mechanisms of energetic coupling that are entirely different from those found in all other enzymes using redox energy to drive vectorial proton transport across a bioenergetic membrane.

β€’ Bioblast editor: Gnaiger E

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Hydrogen ion ambiguities in the electron transfer system

Communicated by Gnaiger E (2023-10-08) last update 2023-11-10
Electron (e-) transfer linked to hydrogen ion (hydron; H+) transfer is a fundamental concept in the field of bioenergetics, critical for understanding redox-coupled energy transformations.
Ambiguity alert H+.png
However, the current literature contains inconsistencies regarding H+ formation on the negative side of bioenergetic membranes, such as the matrix side of the mitochondrial inner membrane, when NADH is oxidized during oxidative phosphorylation (OXPHOS). Ambiguities arise when examining the oxidation of NADH by respiratory Complex I or succinate by Complex II.
Ambiguity alert e-.png
Oxidation of NADH or succinate involves a two-electron transfer of 2{H++e-} to FMN or FAD, respectively. Figures indicating a single electron e- transferred from NADH or succinate lack accuracy.
Ambiguity alert NAD.png
The oxidized NAD+ is distinguished from NAD indicating nicotinamide adenine dinucleotide independent of oxidation state.
NADH + H+ β†’ NAD+ +2{H++e-} is the oxidation half-reaction in this H+-linked electron transfer represented as 2{H++e-} (Gnaiger 2023). Putative H+ formation shown as NADH β†’ NAD+ + H+ conflicts with chemiosmotic coupling stoichiometries between H+ translocation across the coupling membrane and electron transfer to oxygen. Ensuring clarity in this complex field is imperative to tackle the apparent ambiguity crisis and prevent confusion, particularly in light of the increasing number of interdisciplinary publications on bioenergetics concerning diagnostic and clinical applications of OXPHOS analysis.


Enzyme: Complex I 

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