R-body

cellstructuremech:r_body · Inclusion · Inclusion body · Proposed

A bacterial proteinaceous inclusion body assembled from Reb proteins that forms a coiled ribbon and can extend into a hollow tube. [DOI:10.1021/acssynbio.5b00237]

Synonyms: R body; refractile body; R-body inclusion

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
R-body Reb proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Protein constituents that assemble into coiled R-body ribbons. `DOI:10.1128/jb.176.12.3559-3567.1994` Heruth et al. 1994 genetically characterized R-body synthesis and assembly determinants in Caedibacter taeniospiralis strains 47 and 116. `DOI:10.1128/mbio.00715-17` Matsuoka et al. 2017 showed that deleting praR derepresses the Azorhizobium caulinodans reb operon and permits R-body production. `DOI:10.1038/s41467-021-24796-0` Wang et al. 2021 showed that Pseudomonas aeruginosa PA14 produces extendable Reb-based R-bodies.

Taxonomic distribution

NCBITaxon:28907 Caedibacter taeniospiralis — COMMON: Caedibacter taeniospiralis strains 47 and 116 carry plasmid-borne R-body systems used to genetically characterize R-body synthesis and assembly. [DOI:10.1128/jb.176.12.3559-3567.1994]
NCBITaxon:208963 Pseudomonas aeruginosa UCBPP-PA14 — COMMON: Pseudomonas aeruginosa PA14 carries an R-body cassette that produces extendable R-bodies. [DOI:10.1038/s41467-021-24796-0]

Canonical examples

NCBITaxon:28907 Caedibacter taeniospiralis — Classical Paramecium endosymbiont species whose strains 47 and 116 were used to genetically characterize R-body synthesis and assembly determinants. [DOI:10.1128/jb.176.12.3559-3567.1994]
NCBITaxon:208963 Pseudomonas aeruginosa UCBPP-PA14 — Opportunistic pathogen strain used to show that a native Pseudomonas Reb cassette produces extendable R-bodies. [DOI:10.1038/s41467-021-24796-0]

Functions

pH-triggered R-body extension — Coiled R-body ribbons can rapidly extend into hollow tubes when acidification triggers the conformational transition.
- DOI:10.1021/acssynbio.5b00237 Polka and Silver 2016 engineered and imaged type 51 R-bodies that extend from coiled ribbons into tubes after acidification.

Mechanism graphs

Reb proteins build extendable R-body ribbons (FUNCTION)

Reb proteins assemble into a coiled R-body ribbon; low pH triggers extension of the coil into a hollow tube.

Subject	Predicate	Object	Evidence
R-body Reb proteins	assemble into	coiled R-body	`DOI:10.1128/mbio.00715-17` Matsuoka et al. 2017 linked derepression of the Azorhizobium caulinodans reb operon to R-body production. `DOI:10.1038/s41467-021-24796-0` Wang et al. 2021 connected the Pseudomonas PA14 R-body cassette with native R-body production.
acidification trigger	triggers extension of	coiled R-body	`DOI:10.1021/acssynbio.5b00237` Polka and Silver 2016 engineered R-bodies whose extension pH could be tuned.
coiled R-body	extends into	extended R-body tube	`DOI:10.1021/acssynbio.5b00237` Polka and Silver 2016 imaged type 51 R-bodies extending from a coil into a tube.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings and component boundaries for structural and assembly-associated R-body Reb proteins. The first R-body record keeps Reb proteins as a broad label-only cohort because Reb loci vary among Caedibacter, derepressed Azorhizobium and Pseudomonas PA14 systems, and this pass did not verify an exact protein-family CURIE for the structural ribbon constituents.

Evidence

DOI:10.1128/jb.176.12.3559-3567.1994 Heruth et al. 1994, 'Characterization of genetic determinants for R body synthesis and assembly in Caedibacter taeniospiralis 47 and 116', Journal of Bacteriology.
DOI:10.1534/g3.112.005231 Raymann et al. 2013, 'A Genomic Survey of Reb Homologs Suggests Widespread Occurrence of R-Bodies in Proteobacteria', G3.
DOI:10.1021/acssynbio.5b00237 Polka and Silver 2016, 'A Tunable Protein Piston That Breaks Membranes to Release Encapsulated Cargo', ACS Synthetic Biology.
DOI:10.1128/mbio.00715-17 Matsuoka et al. 2017, 'Stringent Expression Control of Pathogenic R-body Production in Legume Symbiont Azorhizobium caulinodans', mBio.
DOI:10.1038/s41467-021-24796-0 Wang et al. 2021, 'Pseudomonas aeruginosa PA14 produces R-bodies, extendable sheaths formed from polymorphic proteins', Nature Communications.

Curation history

2026-09-11T13:22:31Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-11T13:23:34Z codex · EXPANDED_RECORD — Added inclusion-body parentage, R-body synonyms, Reb protein component curation, Azorhizobium and Pseudomonas scope, pH-triggered extension function, DOI evidence, a nonmechanistic Reb extension graph, and a Reb grounding TODO.
2026-09-11T13:23:54Z codex · NORMALIZED_GRAPH — Changed the low-pH extension trigger node from CHEMICAL to ENVIRONMENTAL_FACTOR.
2026-09-11T13:33:10Z codex · ADDRESS_REVIEW — Resolved #486 by removing wild-type Azorhizobium from taxonomic scope, resolved #487 by restricting pH-triggered extension evidence to direct acidification data, and resolved #488 by adding Caedibacter taeniospiralis as a directly observed natural producer.

Source: data/structures/inclusion/r_body.yaml