sws2

UniProt ID: O59772
Organism: Schizosaccharomyces pombe 972h-
Review Status: COMPLETE
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Gene Description

Sws2 (SPCC1795.07) is the fission yeast mitochondrial small-subunit ribosomal protein uS13m, a 151-residue nuclear-encoded member of the universal uS13 family that descends from the bacterial (alphaproteobacterial) S13 lineage rather than from the cytosolic uS13/Rps18 lineage. It localizes to mitochondria and, by orthology with Saccharomyces cerevisiae Sws2, is a structural constituent of the 37S small subunit of the mitoribosome, which translates the mitochondrially encoded respiratory-chain and ATP synthase subunits. In the S. cerevisiae mitoribosome structure uS13m sits in the head of the small subunit and contributes to several intersubunit bridges, contacting the large-subunit protein uL5, the mitochondria-specific protein mL46 and helix H62 of the large-subunit rRNA.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0003676 nucleic acid binding
IEA
GO_REF:0000002 		MODIFY
Summary: InterPro2GO mapping from the uS13-like H2TH domain (IPR010979) to nucleic acid binding.
Reason: The H2TH fold of uS13 binds RNA, and in the S. cerevisiae ortholog's mitoribosome structure uS13m directly contacts large-subunit rRNA helix H62 (bridge mB13). The nucleic acid binding term is true but less specific than the evidence; the specific supported activity is rRNA binding. Sws2 and S. cerevisiae Sws2 are in the same PANTHER subfamily (PTHR10871:SF1), which licenses this transfer.
Proposed replacements: rRNA binding
Supporting Evidence:
file:SCHPO/sws2/sws2-uniprot.txt
Belongs to the universal ribosomal protein uS13 family.
file:SCHPO/sws2/sws2-28154081-supplement.txt
mB13! uS13m:!34,!37B38,!41!
file:interpro/panther/PTHR10871/PTHR10871-entries.csv
sws2,151,PTHR10871:SF1,SMALL RIBOSOMAL SUBUNIT PROTEIN US13M
GO:0003723 RNA binding
IEA
GO_REF:0000002 		MODIFY
Summary: InterPro2GO mapping from the uS13 family and signature entries to RNA binding.
Reason: Correct but general. The RNA that uS13 binds is ribosomal RNA; in the S. cerevisiae mitoribosome uS13m residues 34, 37-38 and 41 contact 21S rRNA helix H62 in intersubunit bridge mB13, and the bacterial-lineage uS13 fold contacts small-subunit rRNA in the head. Refine to rRNA binding, a descendant of RNA binding.
Proposed replacements: rRNA binding
Supporting Evidence:
file:SCHPO/sws2/sws2-28154081-supplement.txt
mB13! uS13m:!34,!37B38,!41!
file:SCHPO/sws2/sws2-uniprot.txt
Belongs to the universal ribosomal protein uS13 family.
GO:0003735 structural constituent of ribosome
IBA
GO_REF:0000033 		ACCEPT
Summary: PAINT propagation of structural constituent of ribosome from the family root node PTN000093238, whose seeds include S. cerevisiae Sws2 (SGD:S000005025), the orthologous uS13m.
Reason: Structural constituent of ribosome is the ancestral uS13 function, placed by PAINT at the family root and inherited by both the cytosolic and mitochondrial/bacterial branches. Sws2 sits in PTHR10871:SF1 together with S. cerevisiae Sws2, whose protein is built into the yeast mitoribosome small subunit structure. This is the core molecular function.
Supporting Evidence:
file:SCHPO/sws2/sws2-28154081-supplement.txt
uS13m! Sws2! P53937!
file:interpro/panther/PTHR10871/PTHR10871-entries.csv
SWS2,143,PTHR10871:SF1,SMALL RIBOSOMAL SUBUNIT PROTEIN US13M
file:interpro/panther/PTHR10871/PTHR10871-entries.csv
sws2,151,PTHR10871:SF1,SMALL RIBOSOMAL SUBUNIT PROTEIN US13M
GO:0003735 structural constituent of ribosome
IEA
GO_REF:0000002 		ACCEPT
Summary: InterPro2GO mapping from the uS13 family entries to structural constituent of ribosome.
Reason: Concordant with the IBA row for the same term and with the orthologous S. cerevisiae uS13m being a modelled protein of the mitoribosome small subunit. Core function.
Supporting Evidence:
file:SCHPO/sws2/sws2-uniprot.txt
Belongs to the universal ribosomal protein uS13 family.
file:SCHPO/sws2/sws2-28154081-supplement.txt
uS13m! Sws2! P53937!
GO:0005739 mitochondrion
HDA
PMID:16823372
ORFeome cloning and global analysis of protein localization ... 		ACCEPT
Summary: Genome-wide ORFeome GFP-fusion localization screen in S. pombe placed Sws2 in mitochondria.
Reason: Direct S. pombe localization evidence, curated by UniProt with an experimental evidence code and consistent with uS13m being a mitoribosomal protein. The cached abstract describes the screen but not the individual image; PomBase curators recorded the Sws2 result.
Supporting Evidence:
file:SCHPO/sws2/sws2-uniprot.txt
SUBCELLULAR LOCATION: Mitochondrion {ECO:0000269|PubMed:16823372}.
GO:0005739 mitochondrion
IBA
GO_REF:0000033 		ACCEPT
Summary: PAINT propagation from PTN000093341, the eukaryotic mitochondrial uS13m node, seeded by Arabidopsis, S. cerevisiae Sws2 and N. crassa uS13m.
Reason: PAINT curators placed mitochondrion at the eukaryotic uS13m node and, at the same node, asserted NOT cytosol (IRD) to block the cytosolic propagation from the family root. Sws2 descends from this node and has its own HDA mitochondrial localization, so the IBA is fully consistent.
Supporting Evidence:
file:interpro/panther/PTHR10871/PTHR10871-paint.tsv
AGI_LocusCode:AT1G77750|SGD:S000005025|UniProtKB:Q7S2C2
file:SCHPO/sws2/sws2-uniprot.txt
SUBCELLULAR LOCATION: Mitochondrion {ECO:0000269|PubMed:16823372}.
GO:0005739 mitochondrion
IEA
GO_REF:0000044 		ACCEPT
Summary: UniProt subcellular-location mapping to mitochondrion.
Reason: Derived from UniProt's experimentally supported Mitochondrion subcellular location; consistent with the HDA and IBA rows for the same term.
Supporting Evidence:
file:SCHPO/sws2/sws2-uniprot.txt
SUBCELLULAR LOCATION: Mitochondrion {ECO:0000269|PubMed:16823372}.
GO:0005763 mitochondrial small ribosomal subunit
ISO
GO_REF:0000024 		ACCEPT
Summary: PomBase curator ortholog transfer from S. cerevisiae SWS2.
Reason: S. cerevisiae Sws2 (P53937) is a modelled component (uS13m, chain MM) of the yeast mitoribosome small subunit in the cryo-EM structure, and it shares PANTHER subfamily PTHR10871:SF1 and the PAINT mitochondrial uS13m node PTN000093341 with S. pombe Sws2, so the orthology is phylogenetically grounded and not a name match.
Supporting Evidence:
file:SCHPO/sws2/sws2-28154081-supplement.txt
uS13m! Sws2! P53937!
PMID:28154081
The mitoribosomal small subunit has been built de novo and includes 15S ribosomal RNA (rRNA) and 34 proteins
file:interpro/panther/PTHR10871/PTHR10871-entries.csv
SWS2,143,PTHR10871:SF1,SMALL RIBOSOMAL SUBUNIT PROTEIN US13M
GO:0005763 mitochondrial small ribosomal subunit
NAS
PMID:18245278
Bot1p is required for mitochondrial translation, respiratory... 		ACCEPT
Summary: PomBase NAS from the Bot1p mitochondrial-translation paper.
Reason: The claim is correct and independently supported by the ISO row and the yeast structural data. The cached Bot1p full text does not name sws2; the NAS presumably derives from the curator's reading of that paper's treatment of S. pombe mitoribosomal proteins, and I defer to it rather than second-guess. The term is supported regardless of this row.
Supporting Evidence:
file:SCHPO/sws2/sws2-28154081-supplement.txt
uS13m! Sws2! P53937!
GO:0005840 ribosome
IEA
GO_REF:0000002 		MODIFY
Summary: InterPro2GO mapping from uS13 family entries to ribosome.
Reason: True but general; uS13 family membership cannot tell cytosolic from mitochondrial ribosomes. Sws2 belongs to the mitochondrial/bacterial uS13 subfamily and the specific supported location is the mitochondrial small ribosomal subunit, already carried by the gene (ISO, NAS).
Supporting Evidence:
file:interpro/panther/PTHR10871/PTHR10871-entries.csv
sws2,151,PTHR10871:SF1,SMALL RIBOSOMAL SUBUNIT PROTEIN US13M
file:SCHPO/sws2/sws2-28154081-supplement.txt
uS13m! Sws2! P53937!
GO:0006412 translation
IEA
GO_REF:0000002 		MODIFY
Summary: InterPro2GO mapping from uS13 family entries to translation.
Reason: True but general. Sws2 is a mitoribosome protein, so the process it does work in is mitochondrial translation (already annotated by ISO and NAS), a descendant of translation.
Proposed replacements: mitochondrial translation
Supporting Evidence:
file:SCHPO/sws2/sws2-uniprot.txt
Belongs to the universal ribosomal protein uS13 family.
file:SCHPO/sws2/sws2-28154081-supplement.txt
uS13m! Sws2! P53937!
GO:0015935 small ribosomal subunit
IBA
GO_REF:0000033 		MODIFY
Summary: PAINT propagation of small ribosomal subunit from the family root PTN000093238 (seeds include E. coli S13, cytosolic uS13 proteins and S. cerevisiae Sws2).
Reason: The root-node term is correct for every uS13 protein, but for Sws2 the specific supported component is the mitochondrial small ribosomal subunit (is_a small ribosomal subunit), which the gene already carries by ISO and NAS. PAINT itself separates the mitochondrial branch at PTN000093341 (mitochondrion; NOT cytosol).
Propagation Review
Root cause: TERM SCOPING PROBLEM
Failure modes: GRANULARITY MISMATCH
Sources checked:
PANTHER:PTN000093238 · PTN000093238 SUPPORTS TRANSFER
Root uS13 node; small ribosomal subunit holds for every descendant, including the mitochondrial branch. The transfer is correct; only the granularity is coarser than the mitochondrial small ribosomal subunit term the gene already carries.
Supporting Evidence:
file:interpro/panther/PTHR10871/PTHR10871-paint.tsv
AGI_LocusCode:AT1G77750|SGD:S000005025|UniProtKB:Q7S2C2
file:SCHPO/sws2/sws2-28154081-supplement.txt
uS13m! Sws2! P53937!
GO:0032543 mitochondrial translation
ISO
GO_REF:0000024 		ACCEPT
Summary: PomBase ortholog transfer of mitochondrial translation from S. cerevisiae SWS2.
Reason: As a structural constituent of the mitoribosome small subunit, uS13m does part of the work of mitochondrial translation (it is part of the machine that carries out the process, and in the yeast structure it contributes to intersubunit bridges with uL5, mL46 and rRNA H62). Orthology to S. cerevisiae Sws2 is grounded by shared subfamily PTHR10871:SF1.
Supporting Evidence:
file:SCHPO/sws2/sws2-28154081-supplement.txt
mB9! uS13m:!70!
PMID:28154081
The mitoribosomal subunits are connected through a series of plastic intersubunit bridges
file:SCHPO/sws2/sws2-uniprot.txt
dedicated translation machinery responsible for the synthesis of
GO:0032543 mitochondrial translation
NAS
PMID:18245278
Bot1p is required for mitochondrial translation, respiratory... 		ACCEPT
Summary: PomBase NAS from the Bot1p mitochondrial-translation paper.
Reason: Consistent with the ISO row for the same term and the structural role of uS13m. The cached full text does not name sws2; I defer to the curator for the provenance and accept the claim on the strength of the ortholog structure.
Supporting Evidence:
file:SCHPO/sws2/sws2-28154081-supplement.txt
uS13m! Sws2! P53937!

Core Functions

Structural constituent of the mitochondrial ribosome small subunit (uS13m), located in the subunit head and contributing rRNA- and protein-mediated intersubunit bridges, as part of the machinery for mitochondrial translation.

Molecular Function:
structural constituent of ribosome
Directly Involved In:
mitochondrial translation
Cellular Locations:
mitochondrion
In Complex:
mitochondrial small ribosomal subunit
Supporting Evidence:
  • file:SCHPO/sws2/sws2-28154081-supplement.txt
    uS13m! Sws2! P53937!
  • file:interpro/panther/PTHR10871/PTHR10871-entries.csv
    sws2,151,PTHR10871:SF1,SMALL RIBOSOMAL SUBUNIT PROTEIN US13M
  • file:SCHPO/sws2/sws2-uniprot.txt
    SUBCELLULAR LOCATION: Mitochondrion {ECO:0000269|PubMed:16823372}.

Binds ribosomal RNA within the mitoribosome, including large-subunit rRNA helix H62 at intersubunit bridge mB13 (inferred from the S. cerevisiae ortholog structure).

Molecular Function:
rRNA binding
In Complex:
mitochondrial small ribosomal subunit
Supporting Evidence:
  • file:SCHPO/sws2/sws2-28154081-supplement.txt
    mB13! uS13m:!34,!37B38,!41!

References

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Suggested Questions for Experts

Q: Does S. pombe uS13m form the same intersubunit bridges (mB8-mB10, mB13) as S. cerevisiae uS13m, given that fission-yeast mitoribosome structure has not been determined?

Suggested Experiments

Experiment: Delete or deplete sws2 and measure respiratory growth and 35S labelling of mitochondrial translation products, and determine whether Sws2 co-sediments with the 37S small subunit.

External Prediction Reviews

These computational predictions are reviewed separately from the GOA annotation set used for this review. The assessments below are from this project and do not constitute official GO annotations or endorsement by GO/UniProt. They are not included in the existing annotation review above.

ProtNLM2 External predictions

View prediction review YAML · sws2-protnlm-predictions-review.yaml · Review status: COMPLETE

The broad GO predictions describe established biology; RNA binding is CNN and the remaining predictions are LSP.

Source documents: genes/SCHPO/sws2/sws2-protnlm-source.xml · genes/SCHPO/sws2/sws2-protnlm-source.json · genes/SCHPO/sws2/sws2-uniprot.txt · genes/SCHPO/sws2/sws2-28154081-supplement.txt

Review score: 2 = concordant with evidence; 1 = uncertain; 0 = discordant with evidence. This is an assessment score, not a model probability.

GO:0006412 translation GO_BP
LSP — Less precise than existing annotation Review score: 2/2
Prediction method: ProtNLM2 · Version: pre-release post-processed-2026_02_28k.xml · file:SCHPO/sws2/sws2-protnlm-source.xml
Review rationale: The target has the diagnostic uS13m family domain and mitochondrial localization. Characterized S. cerevisiae mitoribosome structures support transfer of the conserved mitochondrial ribosomal role. Translation is therefore supported, and the existing mitochondrial translation annotation (GO:0032543) is more specific within the biological-process aspect. The generic prediction is LSP.
Supporting Evidence:
GO:0005840 ribosome GO_CC
LSP — Less precise than existing annotation Review score: 2/2
Prediction method: ProtNLM2 · Version: pre-release post-processed-2026_02_28k.xml · file:SCHPO/sws2/sws2-protnlm-source.xml
Review rationale: The target has the diagnostic uS13m family domain and mitochondrial localization. Characterized S. cerevisiae mitoribosome structures support transfer of the conserved mitochondrial ribosomal role. Membership in the mitochondrial small ribosomal subunit is a supported cellular-component annotation and is more specific than ribosome. The predicted broad complex membership is LSP.
Supporting Evidence:
GO:0003723 RNA binding GO_MF
CNN — Correct but not novel Review score: 2/2
Prediction method: ProtNLM2 · Version: pre-release post-processed-2026_02_28k.xml · file:SCHPO/sws2/sws2-protnlm-source.xml
Review rationale: The target carries the diagnostic uS13 domain. In the experimentally determined S. cerevisiae mitoribosome, the homolog Sws2/P53937 is uS13m and contacts rRNA helix H62 (PMID:28154081, supplementary tables S2 and bridge table). This supports transfer of conserved RNA binding to fission-yeast Sws2, without asserting identical bridge geometry. The equivalent RNA-binding annotation already exists in target GOA, so CNN applies.
Supporting Evidence:
GO:1990904 ribonucleoprotein complex GO_CC
LSP — Less precise than existing annotation Review score: 2/2
Prediction method: ProtNLM2 · Version: pre-release post-processed-2026_02_28k.xml · file:SCHPO/sws2/sws2-protnlm-source.xml
Review rationale: The target has the diagnostic uS13m family domain and mitochondrial localization. Characterized S. cerevisiae mitoribosome structures support transfer of the conserved mitochondrial ribosomal role. Membership in the mitochondrial small ribosomal subunit is a supported cellular-component annotation and is more specific than ribonucleoprotein complex. The predicted broad complex membership is LSP.
Supporting Evidence:

Deep Research

Falcon

(sws2-deep-research-falcon.md)

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📚 Additional Documentation

Notes

(sws2-notes.md)

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Protnlm Function Review

(sws2-protnlm-function-review.md)

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📄 View Raw YAML

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