Transmembrane electrochemical H⁺‐potential as a convertible energy source for the living cell

Role of Ca2+ in regulating the level of mitochondrial pyrophosphate

“…It has also been proposed that PPi is involved in respiration in bacteria [2,3] and in mitochondria [4,5]. Skulachev [6] has suggested that PPi may act as an electrochemical potential buffer under certain conditions, and that PPi might be converted to Pi plus electrochemical potential energy. Evidence has also been presented for the transport of PPi across the mitochondrial membrane in exchange for adenine nucleotides via the adenine nucleotide translocase [7-91. of pyrophosphatase activity [12], causes an elevation of intramitochondrial PPi which subsequently inhibits butyrate oxidation.…”

Current-voltage relationships for the plasma membrane and its principal electrogenic pump inNeurospora crassa: I. Steady-state conditions

“…Quite the opposite is true for electrogenic pumps observed in specialized transporting epithelia [-5, 16], as well as for the electrogenic H § pumps studied in plant, fungal, and bacterial cells [20,23,42] and in mitochondria and chloroplasts [14,38]. In these cases large membrane potentials, directly associated with active transport processes, are present under steady-state conditions and are postulated to play at least two major roles in the total cellular or tissue economy: that of distributing energy to gradient-coupled transport systems, and that of coupling redox energy to covalent-bond energy [33,39,44].…”

The Merger of Bioenergetics and Molecular Biology

“…the electrogenic uptake of (.aL+ 1271 and the exchange of ADP for ATP across the mitochondrial inner membrane [34], as well as the heat production by brown-fat mitochondria through the 'uncoupling protein' thermogenin [ 351. Furthermore, similar energy-transducing systems between electron-transfer complexes and ATP synthase were demonstrated in chloroplasts and prokaryotes (see [ 36]), including the light-driven ATP synthesis and ion transport in Halobacteria. Indeed, two classic pieces of evidence in favour of the chemiosmotic hypothesis come from work with the latter systems, namely Jagendorf and Uribe's [37] demonstration of ATP formation caused by acid-base transition of spinach chloroplasts, and a report by Racker and Stoeckenius [38] on the reconstitution of purple membrane vesicles catalysing light-driven proton uptake and ATP formation.…”