small ribosomal subunit

GO:0015935 · Ribonucleoprotein · Ribonucleoprotein complex · Proposed

The smaller of the two subunits of a ribosome. [GO:0015935]

Synonyms: ribosomal small subunit

Part of: ribosome (GO:0005840)

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
small-subunit rRNA	Rna	part of	Reviewed label only (reviewed name; no accession asserted)		1	ESSENTIAL	Structural RNA core of the small ribosomal subunit that forms the bacterial 30S body, platform, and head and carries the decoding center. `DOI:10.1038/35030006` Wimberly et al. 2000 resolved the Thermus thermophilus 30S structure with 16S rRNA forming the body, platform, and head. `DOI:10.1126/science.1060612` Ogle et al. 2001 structurally analyzed 16S rRNA bases in the 30S decoding center during cognate tRNA recognition.
small-subunit ribosomal proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)		21 proteins in Escherichia coli	CONDITIONAL	Proteins that bind and stabilize the folded small-subunit rRNA scaffold to form a functional decoding subunit. `DOI:10.1038/35030006` Wimberly et al. 2000 placed 20 proteins in the Thermus thermophilus 30S structure, mainly on the solvent-exposed surface. `DOI:10.1128/MMBR.00013-07` Kaczanowska and Ryden-Aulin 2007 report 21 protein constituents for the Escherichia coli 30S subunit.

NCBITaxon:274 Thermus thermophilus — Bacterial source of the 3.05 A 30S small-subunit crystal structure used to resolve 16S rRNA and 30S protein placement. [DOI:10.1038/35030006]
NCBITaxon:83333 Escherichia coli K-12 — Reference bacterial strain for the curated Complex Portal 30S small ribosomal subunit composition, CPX-3802. [ComplexPortal:CPX-3802]

mRNA decoding — The bacterial 30S subunit monitors codon-anticodon geometry and selects cognate aminoacyl-tRNAs during translation.
- DOI:10.1126/science.1060612 Ogle et al. 2001 show 16S rRNA A1492, A1493, and G530 rearrangements around the codon-anticodon helix in the 30S decoding site.

In the bacterial 30S subunit, the small-subunit rRNA scaffold positions a decoding center that inspects codon-anticodon geometry.

Subject	Predicate	Object	Evidence
small-subunit rRNA	forms decoding center of	small ribosomal subunit	`DOI:10.1126/science.1060612` Ogle et al. 2001 show the 30S decoding-center bases A1492, A1493, and G530 interacting with the minor groove of the codon-anticodon helix.
small ribosomal subunit	decodes	mRNA codon	`DOI:10.1126/science.1060612` Ogle et al. 2001 structurally analyzed how the 30S subunit recognizes a cognate tRNA anticodon paired with mRNA.

CURATION_TODO (OPEN): Split exact small-subunit rRNA and protein families across bacterial, archaeal, eukaryotic, and organellar ribosomes. The cross-lineage GO:0015935 term covers homologous small ribosomal subunits with different rRNAs and many distinct ribosomal protein families. This first standalone record keeps the composition at coarse reviewed-label-only granularity until each exact source-neutral family is split and grounded.
INTERPRETATION (RESOLVED): Keep ComplexPortal:CPX-3802 scoped to the E. coli 30S source composition instead of making it an equivalent xref. ComplexPortal:CPX-3802 is the Escherichia coli K-12 30S small ribosomal subunit composition, whereas GO:0015935 denotes small ribosomal subunits across bacteria, archaea, eukaryotes, and organelles.

GO:0015935 Gene Ontology cellular-component term for the small ribosomal subunit.
GO:0005840 Gene Ontology cellular-component term for the containing ribosome.
DOI:10.1038/35030006 Wimberly et al. 2000, Structure of the 30S ribosomal subunit, Nature.
DOI:10.1126/science.1060612 Ogle et al. 2001, Recognition of cognate transfer RNA by the 30S ribosomal subunit, Science.

2026-09-15T18:00:29Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-15T18:01:31Z codex · EXPANDED_RECORD — Added GO synonymy, ribosome parthood, broad rRNA and protein-cohort components, bacterial distribution, Thermus and E. coli exemplars, mRNA-decoding function, GO/literature/Complex Portal evidence, a 30S decoding graph, and component-grounding and CPX-3802 scope discussions.
2026-09-15T18:11:34Z codex · REVIEW_FIX — Resolved PR #1008 review issues #1009, #1010, and #1011 by removing the unsupported Bacteria UNIVERSAL distribution row, pruning the redundant aminoacyl-tRNA decoding graph node and edge, and keeping ComplexPortal:CPX-3802 scoped to the E. coli canonical example and CPX-3802 discussion rather than record-level evidence.