Oxidative phosphorylation

Deep research

Generated by just research-trait; source: research/traits/metabolism/oxidative_phosphorylation-deep-research-falcon.md

# Curation report: microbial oxidative phosphorylation

## Trait record and scope

- **Trait label:** Oxidative phosphorylation
- **Trait identifier:** **`METPO:1000803`**
- **Category / kind / status:** METABOLISM / CLASS / REVIEWED
- **Parent:** `METPO:1000060`

### Operational definition

For TraitMech, this trait should mean the **physiological capacity to conserve energy by coupling a membrane-associated respiratory electron-transfer chain to formation of an electrochemical ion gradient, followed by ATP synthesis from ADP and inorganic phosphate through an ion-driven rotary ATP synthase**. In the canonical bacterial pathway, reducing equivalents enter through primary dehydrogenases, electrons pass through a membrane quinone pool to terminal oxidases or reductases, proton motive force (PMF) is generated, and F-type ATP synthase consumes that PMF to make ATP. Recent reviews describe the same core sequence: respiratory complexes convert NADH or FADH₂ energy into a proton electrochemical gradient, and that gradient drives ATP synthase. (tsviklist2022thecpxstress pages 1-2, zharova2023f1·foatpsynthaseatpase pages 1-2)

The trait is **not synonymous with aerobic respiration**. Oxygen is one terminal acceptor, but anaerobic respiratory chains using nitrate or other acceptors can also conserve energy through an ion gradient. Respiratory nitrate reductase Nar, for example, receives electrons from quinol and can support membrane-potential maintenance under oxygen limitation, although the demonstrated *Streptomyces coelicolor* case sustains survival rather than anaerobic growth. (sawers2019anaerobicnitraterespiration pages 1-2)

### Inclusion criteria

A positive mechanistic graph should normally contain evidence for all three modules:

1. **Respiratory redox module:** oxidation of an electron donor and reduction of a terminal acceptor through a membrane-associated chain.
2. **Chemiosmotic module:** generation or maintenance of an H⁺ or, in a defined microbial variant, Na⁺ electrochemical gradient across an energy-transducing membrane.
3. **ATP-synthesis module:** gradient-driven ATP formation by F-type or archaeal/prokaryotic A/V-type ATP synthase.

### Boundary cases

- **Substrate-level phosphorylation** is outside scope because ATP is formed by direct phosphoryl transfer rather than through a respiratory ion gradient.
- **Fermentation alone** is outside scope. Fermentative metabolism may supply respiratory donors, but fermentation does not establish this trait unless an ion-motive respiratory chain and ATP synthase are also demonstrated.
- **Photophosphorylation** is a neighboring but distinct trait: photosystem II and cytochrome b₆f use light-driven electron transfer to generate the gradient. The respiratory bc₁/bcc complexes belong here; photosynthetic b₆f should not be imported into this graph merely because it uses a homologous Q-cycle. (kao2022quinonebindingsites pages 1-3)
- **Flavin-based electron bifurcation alone** is not oxidative phosphorylation. It directly couples exergonic and endergonic redox reactions in a soluble complex and “is not coupled to ATP synthesis”; it can nevertheless be an upstream donor-generating module when reduced ferredoxin subsequently feeds an ion-motive respiratory chain. (muller2018electronbifurcationa pages 1-2)
- **ATP hydrolysis-driven maintenance of PMF** is the reverse activity of an ATPase, not evidence of oxidative phosphorylation unless net gradient-driven ATP synthesis is shown. Some bacterial and archaeal enzymes are physiologically unidirectional or strongly regulated. (zharova2023f1·foatpsynthaseatpase pages 1-2)
- **Presence of respiratory genes alone** establishes genomic potential, not an observed phenotype. This is especially important for MAG-derived reconstructions.

## Candidate nodes

Identifiers below are conservative. Where exact cross-ontology grounding is uncertain or taxon-dependent, a label-only node is preferable to an invented or overly broad CURIE.

### Trait, pathways, and processes

| Candidate node | Suggested grounding | Curation note |
|---|---|---|
| Oxidative phosphorylation | `METPO:1000803` | Root trait node; quote identifier verbatim. |
| Respiratory electron-transport chain | GO term to be selected after ontology lookup; otherwise label-only | Should encompass primary dehydrogenase → quinone → terminal reductase/oxidase. |
| Chemiosmotic coupling | Label-only, or reviewed GO term | Mechanistic bridge between redox chemistry and ATP synthesis. |
| Proton motive force | Label-only; do not equate automatically with a proton-transport GO process | PMF contains electrical and chemical components. |
| Sodium motive force | Label-only | Valid alternative in particular bacteria and archaea, not universal. |
| ATP synthesis coupled to ion translocation | EC/GO term after validation | Product-level endpoint of the graph. |
| Aerobic respiration | GO-groundable neighboring process | A subtype/context, not equivalent to the target trait. |
| Anaerobic respiration | GO-groundable neighboring process | Include only when an alternative acceptor supports ion-gradient energy conservation. |

### Complexes, enzymes, genes, and proteins

| Candidate node | Suggested grounding | Representative genes or subunits | Notes |
|---|---|---|---|
| Proton-translocating NADH:quinone oxidoreductase, complex I/NDH-1 | `EC:7.1.1.2` | bacterial `nuoA–N`; mycobacterial `nuoABCDEFGHIJKLMN` | Oxidizes NADH, reduces quinone, translocates four H⁺ per NADH/2 e⁻ in the canonical enzyme. (grivennikova2024protontranslocatingnadh–ubiquinoneoxidoreductase pages 1-2, bajeli2020terminalrespiratoryoxidases pages 1-2) |
| Type II NADH dehydrogenase, NDH-2 | Label-only pending exact EC confirmation | `ndh`, `ndhA` in *M. tuberculosis* | Feeds electrons to quinone but is non-proton-pumping in the cited mycobacterial system. (bajeli2020terminalrespiratoryoxidases pages 1-2) |
| Succinate dehydrogenase, complex II | `EC:1.3.5.1` | `sdhABCD` family | Connects the TCA cycle to the quinone pool; generally not a primary PMF generator. (borisov2023cytochromebdas pages 1-3, tsviklist2022thecpxstress pages 1-2) |
| Na⁺-translocating NADH:quinone oxidoreductase | Label-only; validate EC/KEGG module before import | `nqrA–F` | Variant primary sodium pump; should be a conditional branch. (mulkidjanian2008thepastand pages 1-2) |
| Cytochrome bc₁ complex | Label-only complex node | `petABC`/taxon-specific nomenclature | Quinol oxidation and Q-cycle proton translocation. |
| Cytochrome bcc–aa₃ supercomplex | Label-only complex node | `qcrABC`, `cta` genes, taxon-specific | Important actinobacterial/mycobacterial branch. |
| Heme-copper terminal oxidase | Label-only superclass | `cyoABCD`, `cox/cta` families | Reduces O₂; pumping stoichiometry varies by family. |

Showing the first 60 of 285 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.