All families / PF09170
PF09170: STN1_2
CST, complex subunit STN1, C terminal
- Curation status
- SEEDED
- Seed status
- EX DUF
- Characterization
- UNSCORED
Grounding
PF09170: CST, complex subunit STN1, C terminal
IPR015253: integrated entry for CST, complex subunit STN1, C terminal
Source description
STN1 is a component of the CST complex, a complex that binds to single-stranded DNA and is required for protecting telomeres from DNA degradation. The CST complex binds single-stranded DNA with high affinity in a sequence-independent manner, while isolated subunits bind DNA with low affinity on their own. In addition to telomere protection, the CST complex probably has a more general role in DNA metabolism at non-telomeric sites. This entry represents the C-terminal region of Stn1 which has two winged helix-turn-helix (wHTH) motifs, wHTH1 and wHTH2 [InterPro reference PUB00053885,InterPro reference PUB00097419]. wHTH1 is structurally similar to that in RPA32 with a large insertion between helices alpha2 and alpha3, unique to Stn1, that may allow interaction with a different set of proteins that function at telomeres such as Ctc1 [InterPro reference PUB00097419]. wHTH2 is most similar to the DNA-binding wHTH motifs of the pur operon repressor and RepE replication initiator, but it does not bind double-stranded DNA [InterPro reference PUB00057805].
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
2 verified sequence examples. FASTA
| UniProt | Protein / organism | Sequence | Provenance |
|---|---|---|---|
| Q8K2X3 | CST complex subunit STN1 Mus musculus | 378 aa; version 2 UniProt 2026_03 | UNIPROT FETCH |
| Q9H668 | CST complex subunit STN1 Homo sapiens | 368 aa; version 2 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
- 1,178
- matches
- 1,210
- proteomes
- 755
- taxa
- 2,397
- structures
- 8
- alphafold models
- 1,016
- domain architectures
- 13
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.