Hydrogen ion pump

high-resolution terminology - matching measurements at high-resolution

Hydrogen ion pump

Description

Mitochondrial hydrogen ion pumps — frequently referred to as "proton pumps" — are large enzyme complexes (CI, CIII, CIV, ATP synthase) spanning the mt-inner membrane mtIM, partially encoded by mtDNA. CI, CIII and CIV are H⁺ pumps that drive hydrogen ions against the electrochemical protonmotive force pmF and thus generating the pmF, driven by electron transfer from reduced substrates to oxygen. In contrast, ATP synthase (also known as CV) is a H⁺ pump that utilizes the exergy of proton flow along the protonmotive force to drive phosphorylation of ADP to ATP.

Communicated by Gnaiger Erich 2020-12-09

Hydrogen ion pump or proton pump

The proton p⁺ is a positively charged subatomic particle. Protons reside in the nucleus of every atom besides the neutrons. A positively charged ion is defined as a cation, which is a molecule with one or more excess protons that are not electrically neutralized by electrons. The simplest cation is the hydrogen ion H⁺, which is a bare nucleus. The hydrogen ion deuterium ²H⁺ contains a proton and a neutron. ¹H⁺ and ²H⁺ are pumped by the proton pumps (Johansson et al 2011), which thus are more generally hydrogen ion pumps. In contrast, a Ca²⁺ pump is a proton pump which does not translocate hydrogen ions.

In his classical paper, Wikstroem (1977) talks about the "translocation of hydrogen ions across the inner mitochondrial membrane". Perhaps it would be important to clarify, that the term 'proton pump' includes all cation pumps, in contrast to the specific hydrogen ion pumps of the electron transfer system.

» See Hydrogen ion

References

Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed. Bioenerg Commun 2020.2. - »Bioblast link«
Johansson AL, Chakrabarty S, Berthold CL, Högbom M, Warshel A, Brzezinski P (2011) Proton-transport mechanisms in cytochrome c oxidase revealed by studies of kinetic isotope effects. Biochim Biophys Acta 1807:1083-94. - »Bioblast link«
Wikstroem MKF (1977) Proton pump coupled to cytochrome c oxidase in mitochondria. Nature 266:271-3. - »Bioblast link«