parasporal crystal

cellstructuremech:parasporal_crystal · Inclusion · Inclusion body · Proposed

A proteinaceous Bacillus thuringiensis inclusion body that accumulates Cry, Cyt, and related pesticidal crystal proteins as a parasporal crystalline deposit. [DOI:10.3390/toxins6123296]

Synonyms: parasporal crystalline inclusion; parasporal body

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
Cry and Cyt pesticidal crystal proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Strain-specific toxin protoxins that crystallize into the parasporal inclusion and can become active against susceptible cells after solubilization and proteolytic activation. `DOI:10.3390/toxins6123296` Palma et al. 2014 review Bacillus thuringiensis parasporal crystalline inclusions as containing Cry and Cyt proteins, plus additional crystal proteins of varied known or unknown activities. `DOI:10.3390/toxins6041222` Ben-Dov 2014 reviews the Bacillus thuringiensis serovar israelensis toxin plasmid and summarizes Cry4Aa, Cry4Ba, Cry11Aa, Cyt1Aa, Cry10Aa, and Cyt2Ba as the polypeptides that form its complex parasporal crystalline body. `DOI:10.1128/aem.50.1.56-62.1985` The Crossref-indexed abstract for Insell and Fitz-James 1985 reports that the Bacillus thuringiensis subsp. israelensis inclusion has two electron-microscopic lattice classes with distinct major polypeptides; the ASM article and PDF were blocked by Cloudflare during curation, so no verbatim snippets were copied.

Taxonomic distribution

NCBITaxon:1428 Bacillus thuringiensis — VARIABLE: Parasporal crystalline inclusions are characteristic of many Bacillus thuringiensis isolates, but crystal protein complements are plasmid-associated and vary among strains. [DOI:10.3390/toxins6123296]

Canonical examples

NCBITaxon:1430 Bacillus thuringiensis serovar israelensis — Serovar with a complex ovoid parasporal inclusion whose electron-microscopic lattice segments and toxin polypeptide classes were resolved biochemically. [DOI:10.1128/aem.50.1.56-62.1985]

Functions

pesticidal protein packaging — Parasporal crystals package Cry, Cyt, and related pesticidal protoxins as insoluble crystalline deposits.
- DOI:10.3390/toxins6123296 Palma et al. 2014 review Cry/Cyt-containing parasporal inclusions and the downstream biocidal activities of Bt crystal proteins.
- DOI:10.1016/j.toxicon.2006.11.022 Bravo, Gill and Soberon 2007 review Cry and Cyt toxins as Bacillus thuringiensis protein families that form pores in target membranes after activation.

Mechanism graphs

Cry and Cyt proteins crystallize into parasporal toxin inclusions (ASSEMBLY)

A strain-specific set of Bacillus thuringiensis Cry, Cyt, or related pesticidal protoxins accumulates as an insoluble parasporal crystalline body.

Subject	Predicate	Object	Evidence
Cry and Cyt pesticidal crystal proteins	crystallize into	parasporal crystal	`DOI:10.3390/toxins6123296` Palma et al. 2014 review Bt parasporal crystalline inclusions as Cry- and Cyt-containing structures. `DOI:10.1128/aem.50.1.56-62.1985` Insell and Fitz-James 1985 used electron microscopy and polypeptide analysis to subdivide the Bacillus thuringiensis serovar israelensis inclusion into crystalline protein segments.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings for the pesticidal proteins that build Bacillus thuringiensis parasporal crystals. This first pass intentionally models Cry, Cyt and related pesticidal crystal proteins as a broad label-only component because Bt isolates can encode multiple unrelated crystal-protein families. A follow-up should split exact family components only where the family term matches a source-neutral parasporal-crystal constituent.
CURATION_TODO (OPEN): Decide whether Bacillus thuringiensis serovar israelensis parasporal-crystal light and dark segments warrant components or child structures. Insell and Fitz-James resolved two lattice classes with distinct major polypeptide profiles in the Bti ovoidal inclusion. They are represented here only as evidence for protein crystallization because their exact mapping to modern Cry/Cyt toxin names and their suitability as source-neutral structures need a dedicated review.

Evidence

DOI:10.1128/aem.50.1.56-62.1985 Insell and Fitz-James 1985, Composition and Toxicity of the Inclusion of Bacillus thuringiensis subsp. israelensis, Applied and Environmental Microbiology; Crossref abstract consulted because the ASM full text was blocked by Cloudflare.
DOI:10.3390/toxins6041222 Ben-Dov 2014, Bacillus thuringiensis subsp. israelensis and Its Dipteran-Specific Toxins, Toxins; PubMed Central full text and PubMed/Crossref metadata consulted; the MDPI landing page returned access denied in the curation environment.
DOI:10.3390/toxins6123296 Palma et al. 2014, Bacillus thuringiensis Toxins: An Overview of Their Biocidal Activity, Toxins; PubMed Central full text and PubMed/Crossref metadata consulted; the MDPI landing page returned access denied in the curation environment.

Curation history

2026-09-22T11:17:02Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-22T11:18:20Z codex · EXPANDED_RECORD — Added GO:0016234 inclusion-body parentage, parasporal-body synonyms, a reviewed-label-only Cry/Cyt crystal-protein component, Bacillus thuringiensis taxonomic scope, a Bti canonical example, pesticidal protein packaging function, record-level evidence, a nonmechanistic Cry/Cyt crystallization graph, and follow-up grounding/substructure discussions.
2026-09-22T11:32:36Z codex · ADDRESSED_PR_REVIEW — Scoped the Cry/Cyt packaging function and assembly graph to the observed protein-to-crystal relationship; updated Toxins review notes after consulting PubMed Central full text.

Source: data/structures/inclusion/parasporal_crystal.yaml