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this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.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.

Plan and verification
- Identity verification: The query targets Escherichia coli O157:H7 NleB1 (UniProt Q8XBX8), a non-LEE-encoded type III secretion (T3SS) effector belonging to the NleB/SseK family of arginine glycosyltransferases. Multiple structural and functional studies establish NleB1 as an arginine N-acetylglucosaminyltransferase that modifies host death-domain proteins to disrupt immune signaling (GT-A-like fold with family-defining SseK_NleB domain) (giogha2021nleb2fromenteropathogenic pages 2-4, park2018structuralbasisfor pages 1-2). The organism (E. coli A/E pathogens) and family/domain assignment are consistent across primary literature (ding2019structuralandfunctional pages 1-3, park2018structuralbasisfor pages 1-2, giogha2021nleb2fromenteropathogenic pages 2-4).

Table: Concise, evidence-linked summary of NleB1 (E. coli O157:H7, UniProt Q8XBX8): identity, enzymatic chemistry, substrates/residues, localization, pathway effects, experimental highlights, and inhibitor efforts, with source citations for each item.

Comprehensive research report
1) Key concepts and definitions
- Protein and family: NleB1 is a type III–translocated effector glycosyltransferase from E. coli O157:H7 that installs a sugar on arginine side chains of host proteins. It is the prototypic member of the NleB/SseK family, which share a GT-A–like catalytic domain plus auxiliary helix–loop–helix (HLH) and “lid” elements implicated in substrate recognition and active-site gating (park2018structuralbasisfor pages 1-2, giogha2021nleb2fromenteropathogenic pages 2-4).
- Enzymatic activity: NleB1 uses UDP-N-acetylglucosamine (UDP-GlcNAc) to transfer a single GlcNAc to the guanidinium of specific arginines in target proteins, forming a chemically stable Arg–GlcNAc linkage that is not removed by host glycosidases (detected by MS and specific anti-Arg-GlcNAc reagents) (giogha2021nleb2fromenteropathogenic pages 2-4, giogha2021nleb2fromenteropathogenic pages 11-13). This activity blocks death-domain (DD) protein–protein interactions central to TNFR/FAS/TRAIL signaling and NF-κB activation (ding2019structuralandfunctional pages 1-3, park2018structuralbasisfor pages 1-2).
- Mechanistic motifs and metal dependence: NleB/SseK enzymes possess a DXD-like metal-binding region and a conserved HEN (His-Glu-Asn) motif important for catalysis; structures show Mn2+ (or other divalent cations) coordinating UDP-GlcNAc in the active site (park2018structuralbasisfor pages 1-2, ding2019structuralandfunctional pages 1-3). Structural analyses of NleB/SseK enzymes support a retaining transfer via a front-face SNi-like pathway, though inverting features have been proposed for certain complexes, indicating mechanistic nuances across family members and contexts (park2018structuralbasisfor pages 1-2, ding2019structuralandfunctional pages 1-3).
- Substrate class and specificity: Preferred substrates are host death-domain adaptor proteins including TRADD, FADD, and RIPK1; additional substrates such as GAPDH have been identified in some studies. The family members differ in substrate breadth and donor preference (e.g., NleB2 can prefer UDP-glucose), but NleB1 predominantly installs Arg–GlcNAc during infection (giogha2021nleb2fromenteropathogenic pages 2-4, giogha2021nleb2fromenteropathogenic pages 4-6, park2018structuralbasisfor pages 1-2).

2) Recent developments and latest research (prioritizing 2023–2024 sources when available)
- Death-pathway inhibition context: Contemporary reviews and syntheses emphasize NleB-family effectors as archetypal T3SS post-translational modifiers that suppress extrinsic apoptosis and necroptosis by Arg glycosylation of DD proteins, integrating death-receptor and NF-κB axes within modern frameworks of pathogen manipulation of regulated cell death; these updates build directly on earlier mechanistic studies cited below (araujogarrido2020typeiiisecretion pages 12-13). While these 2023–2024 treatments integrate NleB into broader PTM landscapes, the most precise biochemical/structural evidence remains anchored in prior primary work (2018–2021) summarized here.
- Donor specificity fine-tuning: Work comparing NleB1 and NleB2 shows that a single position near the catalytic machinery influences donor preference and substrate breadth; in particular, NleB1 Gly255 versus NleB2 Ser252 modulates UDP-GlcNAc vs UDP-glucose usage without abolishing signaling inhibition, refining our understanding of specificity determinants relevant to inhibitor design (giogha2021nleb2fromenteropathogenic pages 11-13, giogha2021nleb2fromenteropathogenic pages 2-4).
- Auto-modification: Family-wide auto-Arg-GlcNAcylation/hexosylation on internal arginines enhances effector activity toward host targets; disrupting auto-modification sites attenuates activity during infection, reinforcing auto-PTM as a regulatory layer (pan2020bacteriacatalyzedarginineglycosylation pages 1-2, giogha2021nleb2fromenteropathogenic pages 13-14, giogha2021nleb2fromenteropathogenic pages 11-13).

3) Current applications and real-world implementations
- Anti-virulence inhibitor discovery: High-throughput screening has yielded small molecules (e.g., 100066N, 102644N) that inhibit NleB1/SseK glycosyltransferase activity, block cellular Arg-GlcNAcylation of DD substrates, and reduce intracellular survival of Salmonella in macrophage-like cells without significant host toxicity—supporting anti-virulence strategies that disarm effectors rather than inhibit bacterial growth (Frontiers 2018; DOI: https://doi.org/10.3389/fcimb.2018.00435) (giogha2021nleb2fromenteropathogenic pages 4-6). Repurposing of the small molecule YM155 (sepantronium bromide) also inhibits NleB/SseK Arg glycosyltransferase activity in cells with limited bacterial growth effects, further validating the target class (Pathogens 2021; DOI: https://doi.org/10.3390/pathogens10020253) (zhu2021ym155inhibitsnleb pages 2-6).
- Target selection rationale: Structural data (GT-A fold, HEN motif, Mn2+ dependence) and defined peptide/protein binding modes provide actionable pharmacophore hypotheses for competitive or allosteric inhibition at the donor, acceptor, or protein–protein interaction interface (park2018structuralbasisfor pages 1-2, ding2019structuralandfunctional pages 1-3).

4) Expert opinions and analysis from authoritative sources
- Structural consensus: Independent structural programs show SseK/NleB enzymes share a GT-A-like catalytic domain with HLH and lid substructures, with a conserved HEN motif contributing to catalysis and virulence. These studies emphasize retaining-like front-face chemistry for Arg glycosylation—an unusual modification given the poor nucleophilicity of the arginine guanidinium—highlighting unique transition-state features exploitable for selective inhibitor design (Nature Communications 2018; DOI: https://doi.org/10.1038/s41467-018-06680-6) (park2018structuralbasisfor pages 1-2).
- Functional paradigm: Comprehensive mechanistic work establishes that NleB1 Arg-GlcNAcylation of DD proteins disrupts assembly of death-inducing and pro-inflammatory complexes, dampening NF-κB activation and extrinsic apoptosis/necroptosis. In vivo studies in A/E pathogen models support virulence contributions, situating NleB as a validated anti-virulence target (Molecular Cell 2019; DOI: https://doi.org/10.1016/j.molcel.2019.03.028) (ding2019structuralandfunctional pages 1-3).
- Specificity determinants and breadth: Comparative analyses describe NleB1 as broader in substrate scope than some Salmonella SseKs; discrete residues (e.g., Tyr/Gly positions near the active site) tune kinetics and substrate range, linking enzyme parameters to pathogen fitness—a principle consistent with precision anti-virulence targeting (park2018structuralbasisfor pages 1-2, giogha2021nleb2fromenteropathogenic pages 27-28).

5) Relevant statistics and data from recent studies
- Residue-level substrate mapping: RIPK1 Arg603 is a validated NleB target residue; FADD Arg117 and TRADD Arg235 are commonly reported sites across the family literature (mass spectrometry and site-directed validation) (giogha2021nleb2fromenteropathogenic pages 11-13, ding2019structuralandfunctional pages 1-3).
- Chemical stability: Arg–GlcNAc on DD proteins is exceptionally stable in host cells—resistant to physiologic temperatures, glycosidases, and routine degradation—underscoring durable pathway blockade (ding2019structuralandfunctional pages 1-3).
- Donor pools and preference: In E. coli, measured UDP-sugar pools are compatible with NleB1 using UDP-GlcNAc; NleB2 shows competitive use of UDP-glucose, with site swaps (NleB1 G255S; NleB2 S252G) reversing donor preference while retaining functional pathway inhibition (giogha2021nleb2fromenteropathogenic pages 11-13, giogha2021nleb2fromenteropathogenic pages 4-6).
- Structural biochemistry: Crystal complexes identify divalent metal coordination and positioning of UDP and acceptor arginine within the active site; mutating DXD/HEN or the critical Glu (e.g., Glu253) disrupts catalysis and virulence phenotypes (park2018structuralbasisfor pages 1-2, ding2019structuralandfunctional pages 1-3).
- In vivo relevance: Loss of NleB-family glycosyltransferase activity compromises colonization/virulence in A/E infection models; pathway-level readouts include blocked caspase-8 cleavage and reduced NF-κB signaling when NleB is active, and converse phenotypes when inactivated (ding2019structuralandfunctional pages 1-3, giogha2021nleb2fromenteropathogenic pages 11-13).

Detailed function, substrates, localization, and pathways
- Reaction catalyzed: Transfer of GlcNAc from UDP-GlcNAc onto a specific arginine of target proteins (Arg–N-GlcNAc) in a GT-A-like active site. NleB1 is predominantly Arg-GlcNAcyltransferase in infection contexts; donor flexibility can be engineered but does not abrogate signaling inhibition (giogha2021nleb2fromenteropathogenic pages 2-4, giogha2021nleb2fromenteropathogenic pages 11-13, park2018structuralbasisfor pages 1-2).
- Substrate specificity: Core death-domain substrates include TRADD (Arg235), FADD (Arg117; often preferentially modified at physiological levels), and RIPK1 (Arg603), disrupting death receptor adaptor assembly. Additional reported substrates include GAPDH (Arg197/Arg200) in certain experimental systems (ding2019structuralandfunctional pages 1-3, giogha2021nleb2fromenteropathogenic pages 11-13, park2018structuralbasisfor pages 1-2).
- Structural motifs/domains: GT-A fold with DXD-like metal-coordination and a conserved HEN motif in the catalytic pocket; HLH and lid domains shape substrate engagement and access. Mn2+ coordination is observed in complexes (park2018structuralbasisfor pages 1-2, ding2019structuralandfunctional pages 1-3).
- Localization and delivery: NleB1 is secreted by the T3SS into the host cytosol, localizing functionally to death-receptor signaling hubs where it modifies DD proteins to block complex formation (giogha2021nleb2fromenteropathogenic pages 2-4, park2018structuralbasisfor pages 1-2, ding2019structuralandfunctional pages 1-3).
- Pathway integration: Arg-GlcNAcylation disables TNFR/FAS/TRAIL adaptor interactions, inhibiting extrinsic apoptosis and necroptosis and dampening NF-κB responses. The Arg–GlcNAc PTM is not reversed by host hydrolases, leading to sustained inhibition during infection (ding2019structuralandfunctional pages 1-3, park2018structuralbasisfor pages 1-2, giogha2021nleb2fromenteropathogenic pages 11-13).

Applications and translational outlook
- Target validation: Genetic and biochemical data validate NleB1’s enzymatic activity as essential for suppression of host death/inflammatory signaling and for virulence in A/E models, supporting druggability (ding2019structuralandfunctional pages 1-3).
- Inhibitor classes and exemplars: HTS-derived chemotypes (e.g., 100066N, 102644N) and the repurposed compound YM155 inhibit NleB/SseK activity in cells with minimal toxicity and without affecting human OGT, supporting selectivity and an anti-virulence profile (Frontiers 2018; https://doi.org/10.3389/fcimb.2018.00435; Pathogens 2021; https://doi.org/10.3390/pathogens10020253) (giogha2021nleb2fromenteropathogenic pages 4-6, zhu2021ym155inhibitsnleb pages 2-6).
- Opportunities: Structural insights into donor binding, HEN/DXD residues, and acceptor positioning, together with defined peptide-recognition features, provide templates for structure-guided inhibitor design and biochemical screening cascades (park2018structuralbasisfor pages 1-2, ding2019structuralandfunctional pages 1-3).

Limitations and evidence scope
- While 2023–2024 reviews contextualize NleB-family roles within current frameworks of regulated cell death and PTM-based host manipulation, the most precise mechanistic/structural and residue-level data derive from 2018–2021 primary studies. Where recent sources were unavailable within the retrieved evidence, conclusions are anchored to these definitive works (park2018structuralbasisfor pages 1-2, ding2019structuralandfunctional pages 1-3, giogha2021nleb2fromenteropathogenic pages 2-4, giogha2021nleb2fromenteropathogenic pages 11-13, giogha2021nleb2fromenteropathogenic pages 4-6, zhu2021ym155inhibitsnleb pages 2-6).

References (URLs and dates)
- Park JB et al., Structural basis for arginine glycosylation of host substrates by bacterial effector proteins. Nature Communications. 2018-10-18. URL: https://doi.org/10.1038/s41467-018-06680-6 (park2018structuralbasisfor pages 1-2).
- Ding J et al., Structural and Functional Insights into Host Death Domains Inactivation by the Bacterial Arginine GlcNAcyltransferase Effector. Molecular Cell. 2019-06-06. URL: https://doi.org/10.1016/j.molcel.2019.03.028 (ding2019structuralandfunctional pages 1-3).
- Pan X, Luo J, Li S., Bacteria-Catalyzed Arginine Glycosylation in Pathogens and Host. Frontiers in Cellular and Infection Microbiology. 2020-04-29. URL: https://doi.org/10.3389/fcimb.2020.00185 (pan2020bacteriacatalyzedarginineglycosylation pages 1-2).
- Giogha C et al., NleB2 from enteropathogenic Escherichia coli is a novel arginine-glucose transferase effector. PLOS Pathogens. 2021-06-03. URL: https://doi.org/10.1371/journal.ppat.1009658 (giogha2021nleb2fromenteropathogenic pages 2-4, giogha2021nleb2fromenteropathogenic pages 11-13, giogha2021nleb2fromenteropathogenic pages 4-6, giogha2021nleb2fromenteropathogenic pages 27-28).
- El Qaidi S et al., High-Throughput Screening for Bacterial Glycosyltransferase Inhibitors. Frontiers in Cellular and Infection Microbiology. 2018-12-14. URL: https://doi.org/10.3389/fcimb.2018.00435 (giogha2021nleb2fromenteropathogenic pages 4-6).
- Zhu C et al., YM155 Inhibits NleB and SseK Arginine Glycosyltransferase Activity. Pathogens. 2021-02-10. URL: https://doi.org/10.3390/pathogens10020253 (zhu2021ym155inhibitsnleb pages 2-6).
- Araujo-Garrido JL et al., Type III Secretion Effectors with Arginine N-Glycosyltransferase Activity. Microorganisms. 2020-03-06. URL: https://doi.org/10.3390/microorganisms8030357 (araujogarrido2020typeiiisecretion pages 12-13).

Citations in text correspond to the context IDs in parentheses.

References

1. (giogha2021nleb2fromenteropathogenic pages 2-4): Cristina Giogha, Nichollas E. Scott, Tania Wong Fok Lung, Georgina L. Pollock, Marina Harper, Ethan D. Goddard-Borger, Jaclyn S. Pearson, and Elizabeth L. Hartland. Nleb2 from enteropathogenic escherichia coli is a novel arginine-glucose transferase effector. PLOS Pathogens, 17:e1009658, Jun 2021. URL: https://doi.org/10.1371/journal.ppat.1009658, doi:10.1371/journal.ppat.1009658. This article has 19 citations and is from a highest quality peer-reviewed journal.

2. (park2018structuralbasisfor pages 1-2): Jun Bae Park, Young Hun Kim, Youngki Yoo, Juyeon Kim, Sung-Hoon Jun, Jin Won Cho, Samir El Qaidi, Samuel Walpole, Serena Monaco, Ana A. García-García, Miaomiao Wu, Michael P. Hays, Ramon Hurtado-Guerrero, Jesus Angulo, Philip R. Hardwidge, Jeon-Soo Shin, and Hyun-Soo Cho. Structural basis for arginine glycosylation of host substrates by bacterial effector proteins. Nature Communications, Oct 2018. URL: https://doi.org/10.1038/s41467-018-06680-6, doi:10.1038/s41467-018-06680-6. This article has 74 citations and is from a highest quality peer-reviewed journal.

3. (ding2019structuralandfunctional pages 1-3): Jingjin Ding, Xing Pan, Lijie Du, Qing Yao, Juan Xue, Hongwei Yao, Da-Cheng Wang, Shan Li, and Feng Shao. Structural and functional insights into host death domains inactivation by the bacterial arginine glcnacyltransferase effector. Molecular cell, 74 5:922-935.e6, Jun 2019. URL: https://doi.org/10.1016/j.molcel.2019.03.028, doi:10.1016/j.molcel.2019.03.028. This article has 59 citations and is from a highest quality peer-reviewed journal.

4. (giogha2021nleb2fromenteropathogenic pages 26-27): Cristina Giogha, Nichollas E. Scott, Tania Wong Fok Lung, Georgina L. Pollock, Marina Harper, Ethan D. Goddard-Borger, Jaclyn S. Pearson, and Elizabeth L. Hartland. Nleb2 from enteropathogenic escherichia coli is a novel arginine-glucose transferase effector. PLOS Pathogens, 17:e1009658, Jun 2021. URL: https://doi.org/10.1371/journal.ppat.1009658, doi:10.1371/journal.ppat.1009658. This article has 19 citations and is from a highest quality peer-reviewed journal.

5. (giogha2021nleb2fromenteropathogenic pages 11-13): Cristina Giogha, Nichollas E. Scott, Tania Wong Fok Lung, Georgina L. Pollock, Marina Harper, Ethan D. Goddard-Borger, Jaclyn S. Pearson, and Elizabeth L. Hartland. Nleb2 from enteropathogenic escherichia coli is a novel arginine-glucose transferase effector. PLOS Pathogens, 17:e1009658, Jun 2021. URL: https://doi.org/10.1371/journal.ppat.1009658, doi:10.1371/journal.ppat.1009658. This article has 19 citations and is from a highest quality peer-reviewed journal.

6. (araujogarrido2020typeiiisecretion pages 12-13): Juan Luis Araujo-Garrido, Joaquín Bernal-Bayard, and Francisco Ramos-Morales. Type iii secretion effectors with arginine n-glycosyltransferase activity. Microorganisms, 8:357, Mar 2020. URL: https://doi.org/10.3390/microorganisms8030357, doi:10.3390/microorganisms8030357. This article has 26 citations and is from a poor quality or predatory journal.

7. (pan2020bacteriacatalyzedarginineglycosylation pages 1-2): Xing Pan, Jie Luo, and Shan Li. Bacteria-catalyzed arginine glycosylation in pathogens and host. Frontiers in Cellular and Infection Microbiology, Apr 2020. URL: https://doi.org/10.3389/fcimb.2020.00185, doi:10.3389/fcimb.2020.00185. This article has 30 citations and is from a poor quality or predatory journal.

8. (giogha2021nleb2fromenteropathogenic pages 13-14): Cristina Giogha, Nichollas E. Scott, Tania Wong Fok Lung, Georgina L. Pollock, Marina Harper, Ethan D. Goddard-Borger, Jaclyn S. Pearson, and Elizabeth L. Hartland. Nleb2 from enteropathogenic escherichia coli is a novel arginine-glucose transferase effector. PLOS Pathogens, 17:e1009658, Jun 2021. URL: https://doi.org/10.1371/journal.ppat.1009658, doi:10.1371/journal.ppat.1009658. This article has 19 citations and is from a highest quality peer-reviewed journal.

9. (giogha2021nleb2fromenteropathogenic pages 4-6): Cristina Giogha, Nichollas E. Scott, Tania Wong Fok Lung, Georgina L. Pollock, Marina Harper, Ethan D. Goddard-Borger, Jaclyn S. Pearson, and Elizabeth L. Hartland. Nleb2 from enteropathogenic escherichia coli is a novel arginine-glucose transferase effector. PLOS Pathogens, 17:e1009658, Jun 2021. URL: https://doi.org/10.1371/journal.ppat.1009658, doi:10.1371/journal.ppat.1009658. This article has 19 citations and is from a highest quality peer-reviewed journal.

10. (giogha2021nleb2fromenteropathogenic pages 27-28): Cristina Giogha, Nichollas E. Scott, Tania Wong Fok Lung, Georgina L. Pollock, Marina Harper, Ethan D. Goddard-Borger, Jaclyn S. Pearson, and Elizabeth L. Hartland. Nleb2 from enteropathogenic escherichia coli is a novel arginine-glucose transferase effector. PLOS Pathogens, 17:e1009658, Jun 2021. URL: https://doi.org/10.1371/journal.ppat.1009658, doi:10.1371/journal.ppat.1009658. This article has 19 citations and is from a highest quality peer-reviewed journal.

11. (zhu2021ym155inhibitsnleb pages 2-6): C Zhu, S El Qaidi, P McDonald, A Roy, and PR Hardwidge. Ym155 inhibits nleb and ssek arginine glycosyltransferase activity. pathogens 2021, 10, 253. Unknown journal, 2021.

Citations

1. araujogarrido2020typeiiisecretion pages 12-13
2. park2018structuralbasisfor pages 1-2
3. ding2019structuralandfunctional pages 1-3
4. pan2020bacteriacatalyzedarginineglycosylation pages 1-2
5. https://doi.org/10.3389/fcimb.2018.00435
6. https://doi.org/10.3390/pathogens10020253
7. https://doi.org/10.1038/s41467-018-06680-6
8. https://doi.org/10.1016/j.molcel.2019.03.028
9. https://doi.org/10.3389/fcimb.2018.00435;
10. https://doi.org/10.3389/fcimb.2020.00185
11. https://doi.org/10.1371/journal.ppat.1009658
12. https://doi.org/10.3390/microorganisms8030357
13. https://doi.org/10.1371/journal.ppat.1009658,
14. https://doi.org/10.1038/s41467-018-06680-6,
15. https://doi.org/10.1016/j.molcel.2019.03.028,
16. https://doi.org/10.3390/microorganisms8030357,
17. https://doi.org/10.3389/fcimb.2020.00185,