Shiga toxin 2A subunit (Stx2A) is the catalytic A chain of the AB5 Shiga toxin holotoxin produced by EHEC O157:H7. It is an rRNA N-glycosylase (EC 3.2.2.22) that depurinates a specific adenine in the sarcin-ricin loop of 28S rRNA, thereby inactivating ribosomes and halting protein synthesis. This ribosome-inactivating protein (RIP) activity leads to cell death and is the primary mechanism by which Shiga toxin causes hemolytic uremic syndrome (HUS). Stx2A represents a TRUE TOXIN with direct cytotoxic activity, in contrast to type III effectors like NleB1 that modulate signaling without direct cytotoxicity.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0035821
modulation of process of another organism
|
IEA
GO_REF:0000108 |
KEEP AS NON CORE |
Summary: Correct but overly broad. Stx2A modulates host translation by inactivating ribosomes, which falls under this term. The more specific terms (rRNA N-glycosylase, negative regulation of translation) are more informative.
|
|
GO:0016787
hydrolase activity
|
IEA
GO_REF:0000043 |
KEEP AS NON CORE |
Summary: Correct parent term. rRNA N-glycosylases hydrolyze the N-glycosidic bond between adenine and ribose in rRNA. This is appropriately captured by the more specific child term GO:0030598.
|
|
GO:0017148
negative regulation of translation
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: Correct and core biological process. Stx2A inhibits translation by depurinating the sarcin-ricin loop of 28S rRNA, blocking elongation factor-dependent GTPase activity and halting ribosome function. This is the mechanism of toxicity.
|
|
GO:0030598
rRNA N-glycosylase activity
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: Core molecular function. Stx2A is an rRNA N-glycosylase (EC 3.2.2.22) that removes adenine A4324 from the sarcin-ricin loop of 28S rRNA. This is the defining enzymatic activity of ribosome-inactivating proteins (RIPs). Cryo-EM (2023) and X-ray structures (2024) confirm the mechanism and P-stalk recruitment interface.
|
|
GO:0090729
toxin activity
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: LEGITIMATE toxin annotation. Unlike type III effectors (e.g., NleB1) that modulate signaling, Stx2A is a TRUE TOXIN with direct cytotoxic activity. It inactivates ribosomes, halts protein synthesis, and causes cell death. This is the defining virulence factor of EHEC O157:H7 and causes hemolytic uremic syndrome (HUS) in humans. The GO definition of toxin activity requiring initiating pathogenesis leading to an abnormal, generally detrimental state is clearly met by Stx2A.
|
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template_file: templates/gene_research_go_focused.md
template_variables:
organism: ECO57
gene_id: stx2A
gene_symbol: stx2A
uniprot_accession: A0A9Q6Z964
protein_description: 'RecName: Full=rRNA N-glycosylase {ECO:0000256|ARBA:ARBA00012001};
EC=3.2.2.22 {ECO:0000256|ARBA:ARBA00012001};'
gene_info: Name=stx2A {ECO:0000313|EMBL:AAG55587.1}; OrderedLocusNames=Z1464 {ECO:0000313|EMBL:AAG55587.1};
ORFNames=AU473_13255 {ECO:0000313|EMBL:APA41797.1};
organism_full: Escherichia coli O157:H7.
protein_family: Not specified in UniProt
protein_domains: Ribosome-inact_prot_sf. (IPR036041); Ribosome_inactivat_prot. (IPR001574);
Ribosome_inactivat_prot_CS. (IPR017988); Ribosome_inactivat_prot_sub1. (IPR016138);
Ribosome_inactivat_prot_sub2. (IPR016139)
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citation_count: 30
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'stx2A' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene stx2A (gene ID: stx2A, UniProt: A0A9Q6Z964) in ECO57.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.
BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.
DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'stx2A' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information
Please provide a comprehensive research report on the gene stx2A (gene ID: stx2A, UniProt: A0A9Q6Z964) in ECO57.
The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Research plan status: Identity verification complete; evidence gathered for core function, structure, regulation, OMV delivery, epidemiology, diagnostics, and therapeutic leads. Below, we synthesize the findings into a comprehensive functional annotation.
Comprehensive research report: stx2A (A0A9Q6Z964) in Escherichia coli O157:H7
Verification of target identity and domains
- Gene/protein: stx2A encodes the catalytic A subunit (A chain) of Shiga toxin 2 (Stx2), an AB5 holotoxin produced by Shiga toxin–producing E. coli (STEC), including O157:H7. The A chain is proteolytically cleaved into A1 (catalytic) and A2 fragments; A1 is the rRNA N‑glycosylase (EC 3.2.2.22) that depurinates the sarcin–ricin loop (SRL) of 28S rRNA, inactivating the eukaryotic ribosome (RIP family; ribosome-inactivating protein domains). This matches UniProt’s description and RIP domain annotations (IPR001574; IPR036041; IPR016138; IPR016139; IPR017988). Structural and biochemical work from 2023–2024 confirms the mechanism and the A1 interaction with the ribosomal P‑stalk (JBC 2023; Biochemistry 2024) (kulczyk2023cryoemstructureof pages 1-2, li2024structurefunctionanalysisof pages 1-3).
1) Key concepts and definitions with current understanding
- Architecture: Stx2 is an AB5 toxin. The B subunit forms a pentamer that recognizes host globotriaosylceramide (Gb3) to mediate binding and endocytosis; the A chain contains A1 (enzymatic) linked to A2 (tethered to the B pentamer). A1 is released after furin cleavage and disulfide reduction in the ER and retrotranslocates to the cytosol (JBC 2023; Biochemistry 2024) (kulczyk2023cryoemstructureof pages 1-2, li2024structurefunctionanalysisof pages 1-3).
- Enzymatic reaction and substrate: Stx2A1 is an rRNA N‑glycosylase that removes a specific adenine from the SRL of 28S rRNA, blocking elongation factor–dependent GTPase function and halting translation (Biochemistry 2024; historical/mechanistic summaries) (li2024structurefunctionanalysisof pages 1-3, abyad2021shigatoxin(stx) pages 22-25).
- Ribosome recruitment via P‑stalk: Stx2A1 binds the conserved C‑terminal domains (CTDs) of the ribosomal P‑stalk proteins. Cryo‑EM (JBC 2023) shows the native P‑stalk pentamer engages Stx2a with nanomolar affinity and that the last residues of one P‑protein CTD mediate contact. X‑ray structures (Biochemistry 2024) localize the P‑stalk peptide (P8) binding pocket on Stx2A1 and reveal anchor contacts between the P‑stalk terminal Asp and conserved arginines in Stx2A1; blocking this interface inhibits catalytic activity (kulczyk2023cryoemstructureof pages 1-2, li2024structurefunctionanalysisof pages 1-3).
- Substrate specificity vs Stx1: Comparative work indicates Stx2A1 shows higher affinity for ribosomes and higher catalytic activity than Stx1A1; Stx1 is more dependent on P‑stalk proteins for activity, whereas Stx2A has reduced dependence and distinct surface electrostatics contributing to potency (reviews and mutational analyses) (basu2015dothea pages 10-12, basu2016theroleof pages 57-62, basu2016theroleof pages 189-192, narwankar2019effectofpoint pages 40-44).
- Intracellular trafficking and localization: After Gb3-dependent uptake, Stx2 traffics retrogradely from endosomes to Golgi and ER; A1 is released in the ER and retrotranslocates to the cytosol to act on ribosomes. Structural work highlights a flexible A1–A2 loop and furin-sensitive region consistent with this trafficking pathway (JBC 2023; Biochemistry 2024) (kulczyk2023cryoemstructureof pages 1-2, li2024structurefunctionanalysisof pages 1-3).
- Extracellular delivery modes: In addition to lytic phage release of toxin, EHEC O157 produces outer membrane vesicles (OMVs) that carry virulence cargo; OMVs translocate across polarized intestinal epithelial barriers via paracellular and transcellular routes and do so more efficiently under inflammatory conditions, providing a physiologically plausible delivery route for toxins to reach the circulation (Frontiers in Microbiology 2023) (krsek2023translocationofouter pages 1-2).
2) Recent developments and latest research (prioritizing 2023–2024)
- Structural insights into Stx2A1–P‑stalk interactions: Cryo‑EM of Stx2a bound to native ribosomal P‑stalk defined the interface and conformational changes, highlighting the P‑stalk CTD extremity as the minimal binding element and a druggable surface (JBC, Jan 2023; doi:10.1016/j.jbc.2022.102795) (kulczyk2023cryoemstructureof pages 1-2).
- First X‑ray structures of Stx2A1 and inhibitory peptide complexes: The P‑stalk’s last eight residues (P8) are sufficient for high‑affinity binding and maximal inhibition; the terminal Asp acts as an anchor for conserved arginines in Stx2A1, and blocking this site inhibits depurination and activity (Biochemistry, Mar 2024; doi:10.1021/acs.biochem.3c00733) (li2024structurefunctionanalysisof pages 1-3).
- Small-molecule inhibitors targeting ribosome binding site: Fragment screening identified BTB13086 and analogs that bind Stx2A1 at the P‑stalk interface and inhibit activity—the first compounds reported to target this ribosome‑binding site (ACS Infectious Diseases, Jun 2024; doi:10.1021/acsinfecdis.4c00224) (rudolph2024fragmentscreeningto pages 1-3).
- Antibiotic/SOS induction of stx2: Transcriptomic/proteomic profiling of EHEC EDL933 shows ciprofloxacin robustly induces prophage genes and stx2 expression; stx2A/B transcripts increased ~55‑fold, with large increases in toxin subunits by 12 h, consistent with SOS‑mediated prophage induction and cautions about fluoroquinolone use (PLOS ONE, May 2024; doi:10.1371/journal.pone.0298746) (kijewski2024transcriptomicandproteomic pages 8-11). Reviews and studies reaffirm bacteriophage‑encoded stx and SOS/prophage control, with antibiotic exposure triggering induction (2023–2025 references within; supportive synthesis) (bialobzyski2025insilicopredicted pages 22-26, ngoma2023inductionoflysogenic pages 17-20, ngoma2023inductionoflysogenic pages 50-53).
- OMV translocation across the intestinal barrier: Direct demonstration that EHEC O157 OMVs cross polarized intestinal epithelial monolayers and human colonoids, via para- and transcellular routes, independent of specific OMV virulence cargo; translocation is enhanced under inflammatory conditions (Frontiers in Microbiology, May 2023; doi:10.3389/fmicb.2023.1198945) (krsek2023translocationofouter pages 1-2).
3) Current applications and real-world implementations
- Diagnostics: Routine clinical PCRs detect stx and have driven increased detection of non‑O157 STEC; some assays under-detect specific subtypes (e.g., stx2f). Surveillance in England documented an almost ten-fold rise in LEE‑negative STEC notifications in 2014–2022, enabled by PCR-positive screening algorithms linked to WGS (J Med Microbiol, Feb 2024; doi:10.1099/jmm.0.001790) (rodwell2024clinicalandpublic pages 1-2).
- Therapeutic strategies in development:
- Trafficking inhibitors and antitoxin strategies have been explored historically; 2024 advances include first-in-class small molecules blocking the Stx2A1 P‑stalk interface and peptide-based inhibition informed by high‑resolution structures (ACS Infect Dis 2024; Biochemistry 2024) (rudolph2024fragmentscreeningto pages 1-3, li2024structurefunctionanalysisof pages 1-3).
- Given SOS‑linked induction, clinical guidance continues to caution against antibiotics that trigger prophage and increase Stx production (supported experimentally for fluoroquinolones) (PLOS ONE 2024) (kijewski2024transcriptomicandproteomic pages 8-11).
- Public health surveillance: Epidemiologic genomics shows dynamic acquisition/loss of stx-encoding prophages and emphasizes the need to evaluate pathogenic potential by toxin subtype (e.g., stx2a) and accessory virulence repertoires rather than serogroup alone (J Med Microbiol 2024) (rodwell2024clinicalandpublic pages 1-2).
4) Expert opinions and analysis from authoritative sources
- Structural biochemistry consensus: High‑resolution structures (JBC 2023; Biochemistry 2024) consolidate the model in which Stx2A1 must first bind the ribosomal P‑stalk CTDs to be efficiently recruited to the SRL; the P‑stalk interface is validated as an actionable drug target (kulczyk2023cryoemstructureof pages 1-2, li2024structurefunctionanalysisof pages 1-3).
- Toxicology and comparative potency: Reviews and mechanistic analyses conclude that differences in A1 subunit surface electrostatics and P‑stalk dependence contribute to Stx2’s higher potency relative to Stx1, in addition to B‑subunit differences (Toxins 2015; mechanistic reviews/analyses) (basu2015dothea pages 10-12, basu2016theroleof pages 57-62, basu2016theroleof pages 189-192).
- Clinical microbiology perspective: Population surveillance indicates that stx subtype (notably stx2a and activatable stx2d) correlates with more severe clinical outcomes (bloody diarrhea, hospitalization, HUS), warranting subtype-aware risk assessment in diagnostics and public health responses (J Med Microbiol 2024) (rodwell2024clinicalandpublic pages 1-2).
5) Relevant statistics and data (recent studies)
- Antibiotic induction magnitude: Ciprofloxacin exposure upregulated stx2A/B ~55‑fold at the transcript level, with large increases in Stx2 B (~56‑fold) and A (~9.4‑fold) subunits at 12 h, alongside broad prophage activation (PLOS ONE, May 2024) (kijewski2024transcriptomicandproteomic pages 8-11).
- Epidemiology and burden (England, 2014–2022): LEE‑negative STEC (e.g., O91:H14, O146:H21, O128:H2) showed ~10‑fold increase in detections; 1,417 cases in total. PCR assay performance and WGS improved detection and virulence profiling; subtypes stx2a and stx2d were associated with more severe outcomes (J Med Microbiol, Feb 2024) (rodwell2024clinicalandpublic pages 1-2).
- Mechanistic structural minima for inhibition: The last eight residues of the P‑stalk CTD are the minimal sequence required for optimal affinity and maximal inhibition of Stx2A1; terminal Asp‑to‑Arg contacts in Stx2A1 are critical (Biochemistry, Mar 2024) (li2024structurefunctionanalysisof pages 1-3).
Functional annotation summary for stx2A
- Primary function: Encodes the catalytic A subunit (A1/A2) of the Stx2 AB5 holotoxin. Stx2A1 is an rRNA N‑glycosylase that specifically depurinates the SRL of 28S rRNA, blocking protein synthesis (li2024structurefunctionanalysisof pages 1-3, kulczyk2023cryoemstructureof pages 1-2).
- Substrate specificity: Stx2A1 targets the conserved adenine in the SRL of eukaryotic large subunit rRNA; compared with Stx1A1, Stx2A1 shows higher ribosome affinity and catalytic activity and reduced reliance on P‑stalk protein abundance, contributing to higher in vivo potency (basu2015dothea pages 10-12, basu2016theroleof pages 57-62, basu2016theroleof pages 189-192).
- Cellular localization of action: After Gb3-mediated uptake and retrograde trafficking, A1 is released in the ER and retrotranslocated to the cytosol, where it associates with the ribosomal P‑stalk and depurinates the SRL (kulczyk2023cryoemstructureof pages 1-2, li2024structurefunctionanalysisof pages 1-3).
- Secretion/delivery context in EHEC O157:H7: Toxin gene expression is encoded on inducible lambdoid prophages (stx2). Induction via SOS (e.g., fluoroquinolones) increases stx2 expression and toxin production; OMVs from EHEC O157 translocate across the intestinal barrier, offering a phage‑independent vesicular pathway for toxin dissemination to target tissues (kijewski2024transcriptomicandproteomic pages 8-11, krsek2023translocationofouter pages 1-2, bialobzyski2025insilicopredicted pages 22-26, ngoma2023inductionoflysogenic pages 17-20, ngoma2023inductionoflysogenic pages 50-53).
Selected source details with URLs and dates
- Cryo‑EM structure of Stx2 bound to ribosomal P‑stalk: Journal of Biological Chemistry, 299:102795, Jan 2023. URL: https://doi.org/10.1016/j.jbc.2022.102795 (kulczyk2023cryoemstructureof pages 1-2).
- X‑ray structures and peptide inhibition of Stx2A1–P‑stalk binding: Biochemistry, 63:893–905, Mar 2024. URL: https://doi.org/10.1021/acs.biochem.3c00733 (li2024structurefunctionanalysisof pages 1-3).
- Fragment‑based small‑molecule inhibitors of Stx2A1 ribosome‑binding site: ACS Infectious Diseases, 10:2814–2825, Jun 2024. URL: https://doi.org/10.1021/acsinfecdis.4c00224 (rudolph2024fragmentscreeningto pages 1-3).
- Ciprofloxacin induction of stx2 and prophage: PLOS ONE, 19:e0298746, May 2024. URL: https://doi.org/10.1371/journal.pone.0298746 (kijewski2024transcriptomicandproteomic pages 8-11).
- OMV translocation across intestinal epithelium: Frontiers in Microbiology, 14:1198945, May 2023. URL: https://doi.org/10.3389/fmicb.2023.1198945 (krsek2023translocationofouter pages 1-2).
- Clinical/public health implications; subtype severity and surveillance: Journal of Medical Microbiology, 73(2):001790, Feb 2024. URL: https://doi.org/10.1099/jmm.0.001790 (rodwell2024clinicalandpublic pages 1-2).
- Comparative Stx1/Stx2 A‑subunit properties and P‑stalk dependence (review/analyses): Toxins, 7:1467–1485, Apr 2015. URL: https://doi.org/10.3390/toxins7051467 (basu2015dothea pages 10-12). Additional mechanistic summaries and mutational analyses of A1 contributions to potency and electrostatic determinants: 2016 arXiv syntheses (URLs in records) (basu2016theroleof pages 57-62, basu2016theroleof pages 189-192).
Notes on symbol ambiguity
- The symbol stx2A is consistently used for the Shiga toxin 2 A subunit in STEC E. coli, including O157:H7. No conflicting gene with the same symbol in a different organism was encountered in this evidence set. The protein family/domains and mechanism align with the ribosome-inactivating protein superfamily and UniProt annotations (kulczyk2023cryoemstructureof pages 1-2, li2024structurefunctionanalysisof pages 1-3).
Conclusion
stx2A encodes the catalytic A chain of Stx2, a type II ribosome‑inactivating enzyme that depurinates the SRL of 28S rRNA after Gb3-mediated uptake and retrograde trafficking. Recent structural advances precisely map the A1–P‑stalk interface, validating it as a therapeutic target; first‑in‑class peptide and small‑molecule inhibitors of this site have been reported in 2024. On the regulatory side, stx2 resides on inducible prophages and is strongly upregulated by SOS‑inducing antibiotics like ciprofloxacin. Delivery across the intestinal barrier can be mediated by OMVs in addition to phage‑dependent release. Epidemiologically, stx2a‑harboring strains are more frequently associated with severe disease, guiding diagnostics and surveillance. Together, these findings provide a precise functional annotation and actionable targets for countermeasures against Stx2‑mediated disease (kulczyk2023cryoemstructureof pages 1-2, li2024structurefunctionanalysisof pages 1-3, rudolph2024fragmentscreeningto pages 1-3, kijewski2024transcriptomicandproteomic pages 8-11, krsek2023translocationofouter pages 1-2, rodwell2024clinicalandpublic pages 1-2, basu2015dothea pages 10-12).
References
(kulczyk2023cryoemstructureof pages 1-2): Arkadiusz W. Kulczyk, Carlos Oscar S. Sorzano, Przemysław Grela, Marek Tchórzewski, Nilgun E. Tumer, and Xiao-Ping Li. Cryo-em structure of shiga toxin 2 in complex with the native ribosomal p-stalk reveals residues involved in the binding interaction. Journal of Biological Chemistry, 299:102795, Jan 2023. URL: https://doi.org/10.1016/j.jbc.2022.102795, doi:10.1016/j.jbc.2022.102795. This article has 23 citations and is from a domain leading peer-reviewed journal.
(li2024structurefunctionanalysisof pages 1-3): Xiao-Ping Li, Michael J. Rudolph, Yang Chen, and Nilgun E. Tumer. Structure-function analysis of the a1 subunit of shiga toxin 2 with peptides that target the p-stalk binding site and inhibit activity. Biochemistry, 63:893-905, Mar 2024. URL: https://doi.org/10.1021/acs.biochem.3c00733, doi:10.1021/acs.biochem.3c00733. This article has 7 citations and is from a peer-reviewed journal.
(abyad2021shigatoxin(stx) pages 22-25): Jenna Tawil Abyad. Shiga toxin (stx) ribosomal interactions. Text, Jan 2021. URL: https://doi.org/10.7282/t3-j8h6-z233, doi:10.7282/t3-j8h6-z233. This article has 0 citations and is from a peer-reviewed journal.
(basu2015dothea pages 10-12): Debaleena Basu and Nilgun Tumer. Do the a subunits contribute to the differences in the toxicity of shiga toxin 1 and shiga toxin 2? Toxins, 7:1467-1485, Apr 2015. URL: https://doi.org/10.3390/toxins7051467, doi:10.3390/toxins7051467. This article has 43 citations and is from a poor quality or predatory journal.
(basu2016theroleof pages 57-62): Debaleena Basu. The role of the a1 subunit in the activity of shiga toxins. ArXiv, Jan 2016. URL: https://doi.org/10.7282/t3vh5r4t, doi:10.7282/t3vh5r4t. This article has 1 citations.
(basu2016theroleof pages 189-192): Debaleena Basu. The role of the a1 subunit in the activity of shiga toxins. ArXiv, Jan 2016. URL: https://doi.org/10.7282/t3vh5r4t, doi:10.7282/t3vh5r4t. This article has 1 citations.
(narwankar2019effectofpoint pages 40-44): Revati Narwankar. Effect of point mutations on the toxicity of shiga toxin a1 subunit. Text, Jan 2019. URL: https://doi.org/10.7282/t3-n7wj-6m95, doi:10.7282/t3-n7wj-6m95. This article has 0 citations and is from a peer-reviewed journal.
(krsek2023translocationofouter pages 1-2): Daniel Krsek, Daniel Alejandro Yara, Hana Hrbáčková, Ondřej Daniel, Andrea Mančíková, Stephanie Schüller, and Martina Bielaszewska. Translocation of outer membrane vesicles from enterohemorrhagic escherichia coli o157 across the intestinal epithelial barrier. Frontiers in Microbiology, May 2023. URL: https://doi.org/10.3389/fmicb.2023.1198945, doi:10.3389/fmicb.2023.1198945. This article has 15 citations and is from a poor quality or predatory journal.
(rudolph2024fragmentscreeningto pages 1-3): Michael J. Rudolph, Anastasiia M. Tsymbal, Arkajyoti Dutta, Simon A. Davis, Benjamin Algava, Jacques Y. Roberge, Nilgun E. Tumer, and Xiao-Ping Li. Fragment screening to identify inhibitors targeting ribosome binding of shiga toxin 2. ACS infectious diseases, 10:2814-2825, Jun 2024. URL: https://doi.org/10.1021/acsinfecdis.4c00224, doi:10.1021/acsinfecdis.4c00224. This article has 1 citations and is from a peer-reviewed journal.
(kijewski2024transcriptomicandproteomic pages 8-11): Anne Cecilie Riihonen Kijewski, Ingun Lund Witsø, Arvind Y. M. Sundaram, Ola Brønstad Brynildsrud, Kristin Pettersen, Eirik Byrkjeflot Anonsen, Jan Haug Anonsen, and Marina Elisabeth Aspholm. Transcriptomic and proteomic analysis of the virulence inducing effect of ciprofloxacin on enterohemorrhagic escherichia coli. PLOS ONE, 19:e0298746, May 2024. URL: https://doi.org/10.1371/journal.pone.0298746, doi:10.1371/journal.pone.0298746. This article has 5 citations and is from a peer-reviewed journal.
(bialobzyski2025insilicopredicted pages 22-26): S Bialobzyski. In silico predicted association of non-coding rnas with antiviral defence systems in bovine-derived shiga toxin-producing escherichia coli. Unknown journal, 2025.
(ngoma2023inductionoflysogenic pages 17-20): NNF Ngoma. Induction of lysogenic bacteriophages of shiga toxin-producing escherichia coli by antimicrobial growth promoters used in food-producing animals in south africa. Unknown journal, 2023.
(ngoma2023inductionoflysogenic pages 50-53): NNF Ngoma. Induction of lysogenic bacteriophages of shiga toxin-producing escherichia coli by antimicrobial growth promoters used in food-producing animals in south africa. Unknown journal, 2023.
(rodwell2024clinicalandpublic pages 1-2): Ella V. Rodwell, David R. Greig, Gauri Godbole, and Claire Jenkins. Clinical and public health implications of increasing notifications of lee-negative shiga toxin-producing escherichia coli in england, 2014-2022. Journal of medical microbiology, Feb 2024. URL: https://doi.org/10.1099/jmm.0.001790, doi:10.1099/jmm.0.001790. This article has 4 citations and is from a peer-reviewed journal.
id: A0A9Q6Z964
gene_symbol: stx2A
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:83334
label: Escherichia coli O157:H7
description: 'Shiga toxin 2A subunit (Stx2A) is the catalytic A chain of the AB5
Shiga toxin holotoxin produced by EHEC O157:H7. It is an rRNA N-glycosylase
(EC 3.2.2.22) that depurinates a specific adenine in the sarcin-ricin loop of
28S rRNA, thereby inactivating ribosomes and halting protein synthesis. This
ribosome-inactivating protein (RIP) activity leads to cell death and is the
primary mechanism by which Shiga toxin causes hemolytic uremic syndrome (HUS).
Stx2A represents a TRUE TOXIN with direct cytotoxic activity, in contrast to
type III effectors like NleB1 that modulate signaling without direct cytotoxicity.'
existing_annotations:
- term:
id: GO:0035821
label: modulation of process of another organism
evidence_type: IEA
original_reference_id: GO_REF:0000108
review:
summary: Correct but overly broad. Stx2A modulates host translation by inactivating
ribosomes, which falls under this term. The more specific terms (rRNA N-glycosylase,
negative regulation of translation) are more informative.
action: KEEP_AS_NON_CORE
- term:
id: GO:0016787
label: hydrolase activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: Correct parent term. rRNA N-glycosylases hydrolyze the N-glycosidic bond
between adenine and ribose in rRNA. This is appropriately captured by the more
specific child term GO:0030598.
action: KEEP_AS_NON_CORE
- term:
id: GO:0017148
label: negative regulation of translation
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: Correct and core biological process. Stx2A inhibits translation by
depurinating the sarcin-ricin loop of 28S rRNA, blocking elongation factor-dependent
GTPase activity and halting ribosome function. This is the mechanism of toxicity.
action: ACCEPT
- term:
id: GO:0030598
label: rRNA N-glycosylase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: Core molecular function. Stx2A is an rRNA N-glycosylase (EC 3.2.2.22)
that removes adenine A4324 from the sarcin-ricin loop of 28S rRNA. This is
the defining enzymatic activity of ribosome-inactivating proteins (RIPs).
Cryo-EM (2023) and X-ray structures (2024) confirm the mechanism and P-stalk
recruitment interface.
action: ACCEPT
- term:
id: GO:0090729
label: toxin activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: LEGITIMATE toxin annotation. Unlike type III effectors (e.g., NleB1)
that modulate signaling, Stx2A is a TRUE TOXIN with direct cytotoxic activity.
It inactivates ribosomes, halts protein synthesis, and causes cell death.
This is the defining virulence factor of EHEC O157:H7 and causes hemolytic
uremic syndrome (HUS) in humans. The GO definition of toxin activity requiring
initiating pathogenesis leading to an abnormal, generally detrimental state
is clearly met by Stx2A.
action: ACCEPT
references:
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings: []
- id: GO_REF:0000108
title: Automatic assignment of GO terms using logical inference, based on on inter-ontology
links
findings: []
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: file:ECO57/stx2A/stx2A-deep-research-falcon.md
title: Deep research on Stx2A function and mechanism
findings:
- statement: rRNA N-glycosylase mechanism confirmed
supporting_text: 'Stx2A1 is an rRNA N-glycosylase that removes a specific adenine
from the SRL of 28S rRNA, blocking elongation factor-dependent GTPase function
and halting translation'
- statement: P-stalk recruitment for ribosome targeting
supporting_text: 'Cryo-EM shows the native P-stalk pentamer engages Stx2a with
nanomolar affinity; X-ray structures localize the P-stalk peptide binding
pocket on Stx2A1'
core_functions:
- molecular_function:
id: GO:0030598
label: rRNA N-glycosylase activity
description: >-
Stx2A is an rRNA N-glycosylase (EC 3.2.2.22) that removes adenine A4324 from
the sarcin-ricin loop of 28S rRNA. This is the core enzymatic activity of
ribosome-inactivating proteins (RIPs). The enzyme is recruited to ribosomes
via interaction with the P-stalk pentamer.
directly_involved_in:
- id: GO:0017148
label: negative regulation of translation
- molecular_function:
id: GO:0090729
label: toxin activity
description: >-
Stx2A is a TRUE TOXIN with direct cytotoxic activity. Unlike type III effectors
that modulate signaling, Stx2A directly inactivates ribosomes, halts protein
synthesis, and causes cell death. This is the defining virulence factor of
EHEC O157:H7 and causes hemolytic uremic syndrome (HUS) in humans.
proposed_new_terms: []
suggested_questions: []