Pathway · 5 proteins
Oxidative phosphorylation
Proteins of this group that KEGG places on its “Oxidative phosphorylation” map for Aquifex aeolicus.
How it works
This map covers the membrane complexes that pass electrons along a chain and use the energy to pump protons, and ATP synthase, which uses the proton flow to make ATP. The proteins here belong to complex I, the cytochrome bc1 complex, cytochrome c and cytochrome oxidase, together with the enzymes that make heme A for the oxidase.
Grouped by KEGG pathway map. The explanation above is the atlas’s own; the map itself covers more organisms than Aquifex.
Its proteins
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| Cytochrome c | — | — | heme c | 240 | Step named |
| Cytochrome b | — | — | heme b | 409 | Step named |
| Heme O oxygenase | — | — | heme b | 296 | Step named |
| Protoheme IX farnesyltransferase | 2.5.1.141 | heme b + (2E,6E)-farnesyl diphosphate + H2O = Fe(II)-heme o + diphosphate | — | 292 | Step named |
| Cytochrome c oxidase subunit I | — | — | — | 485 | Step named |
Origins
Could cells have drawn energy from a proton gradient before membranes, pumps and ATP synthase existed?
How it was discovered
- 1961Peter Mitchell proposes that cells make ATP using a proton gradient across a membrane (the chemiosmotic hypothesis), later generally accepted (Nobel Prize 1978).Mitchell, Nature 191:144–148 (1961); Cairns-Smith, Genetic Takeover, p. 337
Martin and Russell proposed that the iron and nickel sulfide compartments of alkaline vents maintained a natural proton flow that could have powered early chemistry.
Deamer notes that the proposed proton potential across vent mineral walls has not yet been demonstrated. He adds that high salt and divalent ions in vent fluids inhibit membrane assembly.
In the cell, a proton gradient is useful only together with a sealed membrane, the pumps that build the gradient and ATP synthase that spends it. Each part is useless without the others.
From the books: Koonin, The Logic of Chance, PDF p. 244; Deamer, Assembling Life, p. 28.
The wider question for this part of the cell: origins for manufacturing cofactors and vitamins.
Sources
- KEGG map aae00190 (enzymes of this organism highlighted)
Other pathways in this group: Heme and quinones · Biotin and lipoate · NAD and flavins · Thiamine and pyridoxal · Folate and pterin chemistry · Lipid and cofactor connections · Coenzyme A · Aspartate-family branches · Amino-acid connections · Folate-linked carbon transfer · Serine, glycine and sulfur · Folate biosynthesis · Thiamine metabolism · Pantothenate and CoA biosynthesis · Glycine, serine and threonine metabolism · Riboflavin metabolism · Nicotinate and nicotinamide metabolism · Biotin metabolism · Cysteine and methionine metabolism · Porphyrin metabolism · Pyruvate metabolism · Not yet placed in a pathway