All families / PF10664
PF10664: NdhM
Cyanobacterial and plastid NDH-1 subunit M
- Curation status
- SEEDED
- Seed status
- EX DUF
- Characterization
- UNSCORED
Grounding
PF10664: Cyanobacterial and plastid NDH-1 subunit M
IPR018922: integrated entry for Cyanobacterial and plastid NDH-1 subunit M
Source description
The proton-pumping NADH:ubiquinone oxidoreductase catalyses the electron transfer from NADH to ubiquinone linked with proton translocation across the membrane. It is the largest, most complex and least understood of the respiratory chain enzymes and is referred to as Complex I. The subunit composition of the enzyme varies between groups of organisms. Complex I originating from mammalian mitochondria contains 45 different proteins, whereas in bacteria, the corresponding complex NDH-1 consists of 14 different polypeptides. Homologues of these 14 proteins are found among subunits of the mitochondrial complex I, and therefore bacterial NDH-1 might be considered a model proton-pumping NADH dehydrogenase with a minimal set of subunits. Escherichia coli NDH-1 readily disintegrates into 3 sub-complexes: a water-soluble NADH dehydrogenase fragment (NuoE, -F, and -G),the connecting fragment (NuoB, -C, -D, and -I), and the membrane fragment (NuoA, -H, -J, -K, -L, -M, -N). In cyanobacteria and their descendants, the chloroplasts of green plants, the subunit composition of NDH-1 remains obscure. The genes for eleven subunits NdhA-NdhK, homologous to the NuoA-NuoD and NuoH-NuoN of the E. coli complex, have been found in the genome of Synechocystis sp. PCC 6803 which has a family of 6 ndhD genes and a family of 3 ndhF genes. Two reported multisubunit complexes, NDH-1L and NDH-1M, represent distinct NDH-1 complexes in the thylakoid membrane of Synechocystis 6803 -cyanobacterium. NDH-1L was shown to be essential for photoheterotrophic cell growth, whereas expression of NDH-1M was a prerequisite for CO2 uptake and played an important role in growth of cells at low CO2. Here we report the subunit composition of these two complexes. Fifteen proteins were discovered in NDH-1L including NdhL, a new component of the membrane fragment, and Ssl1690 (designated as NdhO), a novel peripheral subunit [InterPro reference PUB00072930]. The cyanobacterial NDH-1 complex contains additional subunits, NdhM and NdhN, compared with the minimal set of the bacterial enzyme and these seem to be specific for thylakoid-located NDH-1 of photosynthetic organisms [InterPro reference PUB00044393]. The three subunits of NDH-1, NdhM, NdhN and NdhO are essential for effecting cyclic electron flow around photosystem I, by supplying extra-ATP for photosynthesis in both plastids and cyanobacteria [InterPro reference PUB00045281,InterPro reference PUB00109588].
Evidence and references
- InterPro entry and its literature references. PUB identifiers are internal InterPro references, not PubMed identifiers. Unresolved citations link to the originating entry.
- Frozen description source: InterPro/Pfam API
Source descriptions and links are provenance, not independent functional validation.
Evidence counts: not scored.
Curated functional assertions
No curated functional assertions supplied.
Protein sequence examples
1 verified sequence example. FASTA
| UniProt | Protein / organism | Sequence | Provenance |
|---|---|---|---|
| Q2V2S7 | NAD(P)H-quinone oxidoreductase subunit M, chloroplastic Arabidopsis thaliana | 217 aa; version 1 UniProt 2026_03 | PTM REGISTRY MIRROR |
Pfam membership is not functional evidence. Whole-protein sequences do not establish domain boundaries. A coverage gap here is not absence from UniProt.
Sequences and metadata: UniProt Consortium, CC BY 4.0.
Domain matches
No residue-level domain match evidence is available in this build. Structure and AlphaFold counters do not supply coordinates or establish function.
Snapshot counters
- proteins
- 761
- matches
- 766
- proteomes
- 592
- taxa
- 1,711
- structures
- 14
- alphafold models
- 580
- domain architectures
- 9
Classification basis
pfam previous unknown name
No scoring reasons supplied.
Related Mech records
This family joined the worklist after the frozen cross-Mech scan, so other Mechs were not searched for it. Missing links here are not evidence that other Mechs lack it; rows shown come from mentions of a former DUF/UPF name.
No cross-Mech examples are present in the supplied snapshot.
Curation history and reviews
No retained curation events supplied.
No retained review supplied.
Record source
Status and evidence
- Seed status
- A name-based classification of frozen InterPro/Pfam metadata. UNKNOWN CANDIDATE means the metadata explicitly says the function is unknown. KNOWN HISTORICAL DUF means a DUF name matched without that wording; this heuristic is not proof of a known function and does not establish experimental characterization. EX DUF means Pfam renamed the family away from a DUF/UPF name, as recorded in Pfam's previous identifiers; a rename usually follows published work on some members but is naming history, not proof of function for every member. Some EX DUF families' current names or descriptions still say the function is unknown; their classification basis lists this, and scoring does not treat them as characterized. FALSE POSITIVE TEXT HIT means the naming rules did not match.
- Characterization
- A separate evidence-scoring result. UNSCORED means no score has been calculated; it is not evidence that the family lacks a known function. Missing scores are not negative evidence. PARTIALLY CHARACTERIZED has partial support; KNOWN HISTORICAL DUF can inherit the seed label or reflect a known-function signal. Neither label implies experimental validation.
- Evidence counts
- Source-specific signals, not unique proteins, publications, or confidence scores. Known counts Rhea reactions and experimentally supported GO molecular-function annotations. Partial counts functional/domain assignments. Context counts structural, environmental, orthology, interaction and neighborhood signals; context alone does not assign function. Repeated annotations may not be independent.
- Curation status
- Reported separately from seed classification and characterization. SNAPSHOT ONLY means no curated metadata was supplied for this build. SEEDED denotes a source-derived record, not an expert-reviewed functional claim.
- Missing counts
- Not available means the source did not supply that counter. A zero is a reported count. Not scored means evidence counts are unavailable.