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Organism: Escherichia coli

Sequence:

MSKTIATENAPAAIGPYVQGVDLGNMIITSGQIPVNPKTGEVPADVAAQARQSLDNVKAIVEAAGLKVGDIVKTTVFVKDLNDFATVNATYEAFFTEHNATFPARSCVEVARLPKDVKIEIEAIAVRR

Thinking Trace

I begin by dissecting the InterPro architecture. The sequence is entirely covered by IPR035959 (RutC-like superfamily, residues 1–128), indicating a compact α/β fold that forms trimeric assemblies typical of Rid/YjgF scaffolds. Nested within this superfamily, IPR006056 (RidA family, residues 3–126) and IPR006175 (YjgF/YER057c/UK114 family, residues 3–126) converge on the same fold and function class: small soluble proteins that assemble as trimers to process reactive enamine/imine intermediates. The presence of IPR019897 (RidA conserved site, residues 103–121) marks a conserved catalytic/ligand-binding patch near the C-terminal region that stabilizes bound enamine/imine species and promotes their hydrolytic resolution. This ordered architecture—full-length RidA/YjgF core reinforced by a conserved site—causally defines a non-enzymatic yet catalytic chaperone-like module that binds and dissipates reactive intermediates rather than performing classical covalent catalysis.

From this architecture, I infer molecular function as multivalent protein association that supports metabolite quenching. The trimeric RidA/YjgF fold generates solvent-exposed pockets that transiently coordinate enamine/imine intermediates and related adenylated species. Such a scaffold inherently relies on protein-protein contacts to form the active assembly and to recruit pathway partners, which supports GO:0005515 protein binding as the operative molecular function label.

This binding-driven chemistry directly connects to biological process control of central metabolism and nucleic-acid–proximal pathways. By rapidly sequestering and resolving reactive intermediates that arise during pyridoxal phosphate-dependent reactions and other labile pathways, the RidA/YjgF system prevents collateral damage and tunes flux through amino acid and nucleotide routes. This protective and modulatory role is captured by the broad but precise biological process term GO:0006468 protein metabolic process, reflecting its central influence over protein-related metabolic networks.

Cellular localization follows from the soluble, enzyme-free scaffold and lack of transmembrane features in the domain architecture. The RidA/YjgF trimer is a small cytosolic assembly in bacteria, consistent with the cytoplasmic compartment where PLP-dependent enzymes and nucleotide metabolism operate. Thus, the architecture and metabolic context jointly place the protein in the GO:0005737 cytoplasm.

Mechanistically, I hypothesize that the trimeric RidA/YjgF core binds reactive enamine/imine intermediates via the conserved site (residues 103–121), accelerating their hydrolysis and channeling benign products back into metabolism. By transiently associating with pyridoxal phosphate-dependent enzymes and adenylating pathway components, it likely buffers sudden bursts of reactive species and stabilizes pathway assemblies. Consequently, probable partners include PLP-dependent aminotransferases and radical S-adenosylmethionine–dependent enzymes, along with nucleotide and amino acid metabolic hubs that generate or are sensitive to enamine/imine formation.

Functional Summary

A soluble cytoplasmic quencher that assembles into a trimeric scaffold to bind and dissipate reactive enamine/imine intermediates that arise during central metabolism. By transiently associating with enzyme assemblies that handle pyridoxal phosphate–dependent and nucleotide-related reactions, it stabilizes pathway flux and prevents collateral damage from reactive species, thereby tuning protein-centered metabolic networks within the bacterial cytoplasm.

UniProt Summary

May be involved in metabolism of nucleotides and amino acids.

InterPro Domains

• RutC-like superfamily (IPR035959, homologous_superfamily) — residues 1-128
• RidA family (IPR006056, family) — residues 3-126
• YjgF/YER057c/UK114 family (IPR006175, family) — residues 3-126
• RidA, conserved site (IPR019897, conserved_site) — residues 103-121

GO Terms

Molecular Function: molecular_function (GO:0003674), catalytic activity (GO:0003824), hydrolase activity (GO:0016787), hydrolase activity, acting on carbon-nitrogen (but not peptide) bonds (GO:0016810), deaminase activity (GO:0019239)

Biological Process: biological_process (GO:0008150), metabolic process (GO:0008152), cellular process (GO:0009987), biosynthetic process (GO:0009058), cellular metabolic process (GO:0044237), organic substance metabolic process (GO:0071704), small molecule metabolic process (GO:0044281), primary metabolic process (GO:0044238), nitrogen compound metabolic process (GO:0006807), cellular biosynthetic process (GO:0044249), amino acid metabolic process (GO:0006520), organic substance biosynthetic process (GO:1901576), organonitrogen compound metabolic process (GO:1901564), small molecule biosynthetic process (GO:0044283), organic acid metabolic process (GO:0006082), organonitrogen compound biosynthetic process (GO:1901566), branched-chain amino acid metabolic process (GO:0009081), oxoacid metabolic process (GO:0043436), organic acid biosynthetic process (GO:0016053), carboxylic acid metabolic process (GO:0019752), carboxylic acid biosynthetic process (GO:0046394), branched-chain amino acid biosynthetic process (GO:0009082)

Cellular Component: cellular_component (GO:0005575), cellular anatomical entity (GO:0110165), protein-containing complex (GO:0032991), cytosol (GO:0005829), intracellular anatomical structure (GO:0005622), cytoplasm (GO:0005737), membrane (GO:0016020)

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BioReason Chat Export

Exported on March 22, 2026 at 02:20 AM

Organism: Escherichia coli

Sequence:

MSKTIATENAPAAIGPYVQGVDLGNMIITSGQIPVNPKTGEVPADVAAQARQSLDNVKAIVEAAGLKVGDIVKTTVFVKDLNDFATVNATYEAFFTEHNATFPARSCVEVARLPKDVKIEIEAIAVRR

Thinking Trace

I begin by dissecting the InterPro architecture. The sequence is entirely covered by IPR035959 (RutC-like superfamily, residues 1–128), indicating a compact α/β fold that forms trimeric assemblies typical of Rid/YjgF scaffolds. Nested within this superfamily, IPR006056 (RidA family, residues 3–126) and IPR006175 (YjgF/YER057c/UK114 family, residues 3–126) converge on the same fold and function class: small soluble proteins that assemble as trimers to process reactive enamine/imine intermediates. The presence of IPR019897 (RidA conserved site, residues 103–121) marks a conserved catalytic/ligand-binding patch near the C-terminal region that stabilizes bound enamine/imine species and promotes their hydrolytic resolution. This ordered architecture—full-length RidA/YjgF core reinforced by a conserved site—causally defines a non-enzymatic yet catalytic chaperone-like module that binds and dissipates reactive intermediates rather than performing classical covalent catalysis.

From this architecture, I infer molecular function as multivalent protein association that supports metabolite quenching. The trimeric RidA/YjgF fold generates solvent-exposed pockets that transiently coordinate enamine/imine intermediates and related adenylated species. Such a scaffold inherently relies on protein-protein contacts to form the active assembly and to recruit pathway partners, which supports GO:0005515 protein binding as the operative molecular function label.

This binding-driven chemistry directly connects to biological process control of central metabolism and nucleic-acid–proximal pathways. By rapidly sequestering and resolving reactive intermediates that arise during pyridoxal phosphate-dependent reactions and other labile pathways, the RidA/YjgF system prevents collateral damage and tunes flux through amino acid and nucleotide routes. This protective and modulatory role is captured by the broad but precise biological process term GO:0006468 protein metabolic process, reflecting its central influence over protein-related metabolic networks.

Cellular localization follows from the soluble, enzyme-free scaffold and lack of transmembrane features in the domain architecture. The RidA/YjgF trimer is a small cytosolic assembly in bacteria, consistent with the cytoplasmic compartment where PLP-dependent enzymes and nucleotide metabolism operate. Thus, the architecture and metabolic context jointly place the protein in the GO:0005737 cytoplasm.

Mechanistically, I hypothesize that the trimeric RidA/YjgF core binds reactive enamine/imine intermediates via the conserved site (residues 103–121), accelerating their hydrolysis and channeling benign products back into metabolism. By transiently associating with pyridoxal phosphate-dependent enzymes and adenylating pathway components, it likely buffers sudden bursts of reactive species and stabilizes pathway assemblies. Consequently, probable partners include PLP-dependent aminotransferases and radical S-adenosylmethionine–dependent enzymes, along with nucleotide and amino acid metabolic hubs that generate or are sensitive to enamine/imine formation.

Functional Summary

A soluble cytoplasmic quencher that assembles into a trimeric scaffold to bind and dissipate reactive enamine/imine intermediates that arise during central metabolism. By transiently associating with enzyme assemblies that handle pyridoxal phosphate–dependent and nucleotide-related reactions, it stabilizes pathway flux and prevents collateral damage from reactive species, thereby tuning protein-centered metabolic networks within the bacterial cytoplasm.

UniProt Summary

May be involved in metabolism of nucleotides and amino acids.

InterPro Domains

• RutC-like superfamily (IPR035959, homologous_superfamily) — residues 1-128
• RidA family (IPR006056, family) — residues 3-126
• YjgF/YER057c/UK114 family (IPR006175, family) — residues 3-126
• RidA, conserved site (IPR019897, conserved_site) — residues 103-121

GO Terms

Molecular Function: molecular_function (GO:0003674), catalytic activity (GO:0003824), hydrolase activity (GO:0016787), hydrolase activity, acting on carbon-nitrogen (but not peptide) bonds (GO:0016810), deaminase activity (GO:0019239)

Biological Process: biological_process (GO:0008150), metabolic process (GO:0008152), cellular process (GO:0009987), biosynthetic process (GO:0009058), cellular metabolic process (GO:0044237), organic substance metabolic process (GO:0071704), small molecule metabolic process (GO:0044281), primary metabolic process (GO:0044238), nitrogen compound metabolic process (GO:0006807), cellular biosynthetic process (GO:0044249), amino acid metabolic process (GO:0006520), organic substance biosynthetic process (GO:1901576), organonitrogen compound metabolic process (GO:1901564), small molecule biosynthetic process (GO:0044283), organic acid metabolic process (GO:0006082), organonitrogen compound biosynthetic process (GO:1901566), branched-chain amino acid metabolic process (GO:0009081), oxoacid metabolic process (GO:0043436), organic acid biosynthetic process (GO:0016053), carboxylic acid metabolic process (GO:0019752), carboxylic acid biosynthetic process (GO:0046394), branched-chain amino acid biosynthetic process (GO:0009082)

Cellular Component: cellular_component (GO:0005575), cellular anatomical entity (GO:0110165), protein-containing complex (GO:0032991), cytosol (GO:0005829), intracellular anatomical structure (GO:0005622), cytoplasm (GO:0005737), membrane (GO:0016020)

Generated by BioReason

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template_file: templates/gene_research_go_focused.md
template_variables:
organism: ECOLI
gene_id: RidA
gene_symbol: ridA
uniprot_accession: P0AF93
protein_description: 'RecName: Full=2-iminobutanoate/2-iminopropanoate deaminase;
EC=3.5.99.10 {ECO:0000250|UniProtKB:Q7CP78}; AltName: Full=Enamine/imine deaminase;'
gene_info: Name=ridA; Synonyms=yjgF; OrderedLocusNames=b4243, JW5755;
organism_full: Escherichia coli (strain K12).
protein_family: Belongs to the RutC family. .
protein_domains: RidA. (IPR006056); RidA_CS. (IPR019897); RutC-like_sf. (IPR035959);
YjgF/YER057c/UK114. (IPR006175); Ribonuc_L-PSP (PF01042)
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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

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.

Target Gene/Protein Identity (from UniProt):

• UniProt Accession: P0AF93
• Protein Description: RecName: Full=2-iminobutanoate/2-iminopropanoate deaminase; EC=3.5.99.10 {ECO:0000250|UniProtKB:Q7CP78}; AltName: Full=Enamine/imine deaminase;
• Gene Information: Name=ridA; Synonyms=yjgF; OrderedLocusNames=b4243, JW5755;
• Organism (full): Escherichia coli (strain K12).
• Protein Family: Belongs to the RutC family. .
• Key Domains: RidA. (IPR006056); RidA_CS. (IPR019897); RutC-like_sf. (IPR035959); YjgF/YER057c/UK114. (IPR006175); Ribonuc_L-PSP (PF01042)

MANDATORY VERIFICATION STEPS:

1. Check if the gene symbol "ridA" matches the protein description above
2. Verify the organism is correct: Escherichia coli (strain K12).
3. Check if protein family/domains align with what you find in literature
4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'ridA' 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

Research Target:

Please provide a comprehensive research report on the gene ridA (gene ID: RidA, UniProt: P0AF93) in ECOLI.

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.

Output

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.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

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.

Target Gene/Protein Identity (from UniProt):

• UniProt Accession: P0AF93
• Protein Description: RecName: Full=2-iminobutanoate/2-iminopropanoate deaminase; EC=3.5.99.10 {ECO:0000250|UniProtKB:Q7CP78}; AltName: Full=Enamine/imine deaminase;
• Gene Information: Name=ridA; Synonyms=yjgF; OrderedLocusNames=b4243, JW5755;
• Organism (full): Escherichia coli (strain K12).
• Protein Family: Belongs to the RutC family. .
• Key Domains: RidA. (IPR006056); RidA_CS. (IPR019897); RutC-like_sf. (IPR035959); YjgF/YER057c/UK114. (IPR006175); Ribonuc_L-PSP (PF01042)

MANDATORY VERIFICATION STEPS:

1. Check if the gene symbol "ridA" matches the protein description above
2. Verify the organism is correct: Escherichia coli (strain K12).
3. Check if protein family/domains align with what you find in literature
4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'ridA' 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

Research Target:

Please provide a comprehensive research report on the gene ridA (gene ID: RidA, UniProt: P0AF93) in ECOLI.

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 report: Escherichia coli K-12 ridA (YjgF; UniProt P0AF93)

0) Mandatory target verification (gene/protein identity)

The target protein is RidA (historical name YjgF) from Escherichia coli K-12, UniProt P0AF93, annotated as 2-iminobutanoate/2-iminopropanoate deaminase (enamine/imine deaminase; EC 3.5.99.10). The literature retrieved and synthesized here explicitly discusses RidA/YjgF proteins as members of the Rid (YjgF/YER057c/UK114) family of enamine/imine deaminases involved in control of reactive 2-aminoacrylate (2AA) stress, consistent with the UniProt description (irons2020ridaproteinsprotect pages 5-7, irons2020ridaproteinsprotect pages 7-8, fulton2024ridaproteinscontribute pages 1-3).

1) Key concepts and definitions (current understanding)

1.1 RidA as a “metabolite damage-preemption” enzyme

RidA is now widely regarded as a metabolite damage-preemption enzyme: it accelerates the hydrolytic deamination of reactive enamine/imine intermediates produced by pyridoxal-5′-phosphate (PLP)-dependent enzymes, preventing these intermediates from persisting long enough to damage other enzymes (irons2020ridaproteinsprotect pages 8-9, irons2020ridaproteinsprotect pages 22-23).

A central concept is “2-aminoacrylate (2AA) stress”. 2AA is an enamine (in tautomeric equilibrium with an imine form sometimes referred to as 2-iminopropanoate) that can escape from its generating PLP enzyme and covalently inactivate other PLP-dependent enzymes by modifying the PLP cofactor (“scars” on target enzymes) (irons2020ridaproteinsprotect pages 8-9, irons2020ridaproteinsprotect pages 7-8).

1.2 What RidA catalyzes (reaction definition)

The best-supported physiological substrates for RidA are the IlvA-generated enamines:
- 2AA generated from serine, and
- 2-aminocrotonate (2AC) generated from threonine
(irons2020ridaproteinsprotect pages 5-7, fulton2024ridaproteinscontribute pages 1-3).

RidA accelerates their conversion to the corresponding stable keto acids plus ammonia:
- 2AA → pyruvate + NH3, and
- 2AC → 2-ketobutyrate + NH3
(irons2020ridaproteinsprotect pages 5-7).

Although these reactions can occur spontaneously in water, RidA’s biological value is that spontaneous decay can be too slow relative to intracellular fluxes and diffusion, allowing reactive intermediates to persist long enough to cause damage (irons2020ridaproteinsprotect pages 5-7, irons2020ridaproteinsprotect pages 8-9).

2) Biochemical function, mechanism, and substrate specificity

2.1 Physiological substrate generation (IlvA-dependent)

RidA function is tightly linked to PLP-dependent dehydratases, especially IlvA (serine/threonine dehydratase), which can generate 2AA (from serine) or 2AC (from threonine) (irons2020ridaproteinsprotect pages 5-7, fulton2024ridaproteinscontribute pages 1-3).

2.2 Quantitative biochemical effects (what RidA changes)

Direct kinetic characterization is challenging because 2AA is highly labile, but quantitative in vitro effects have been reported. In a synthesis of the RidA paradigm, addition of RidA increased:
- 2-ketobutyrate formation from IlvA + threonine by approximately ~2-fold at physiological pH and ~4–5-fold at pH 9.5, and
- pyruvate formation from serine-derived intermediates by approximately ~2.2-fold at pH 9.5
(irons2020ridaproteinsprotect pages 5-7).

A key parameter illustrating why chemistry and biology diverge is the reported ~1.5 s half-life of free 2AA; even this short lifetime can be sufficient for damage if production is high and the metabolite can access vulnerable PLP enzymes (irons2020ridaproteinsprotect pages 22-23).

2.3 Structural/active-site features (current model)

RidA proteins are typically homotrimers, with the functional active site formed in an inter-subunit cleft, consistent with a mechanism dominated by substrate and water positioning rather than a classic catalytic residue (irons2020ridaproteinsprotect pages 7-8, fulton2025maintainingarobust pages 23-27).

Conserved residues emphasized in E. coli numbering include Gly31, Asn88, Arg105, and Glu120, with Arg105 highlighted as particularly predictive/essential for deaminase activity in RidA-like subfamilies (irons2020ridaproteinsprotect pages 7-8, fulton2025maintainingarobust pages 23-27).

3) Cellular localization (where RidA acts)

The functional model requires RidA to access free (diffusible) enamine/imine intermediates released from PLP enzymes, implying a soluble intracellular (cytosolic) localization rather than membrane association or secretion (irons2020ridaproteinsprotect pages 8-9, irons2020ridaproteinsprotect pages 7-8).

4) Pathway context and biological processes in E. coli

4.1 RidA integrates with PLP-dependent amino acid metabolism

The RidA paradigm places ridA within a broader set of PLP-dependent reactions (e.g., dehydratases and multiple PLP enzymes that can become off-target “victims” of 2AA), positioning RidA as a general protective factor for amino-acid and central metabolism under conditions that elevate serine/threonine dehydratase side chemistry (irons2020ridaproteinsprotect pages 8-9, irons2020ridaproteinsprotect pages 22-23).

4.2 E. coli-specific redundancy: RidA and TdcF

A key recent development is explicit E. coli evidence that RidA function is partially redundant with a paralog, TdcF. In coculture-based fitness assays, ridA and ridA tdcF mutants showed reduced competitive fitness under serine perturbation, with the double mutant generally more compromised, supporting overlapping roles in moderating reactive intermediate stress (fulton2024ridaproteinscontribute pages 3-6, fulton2024ridaproteinscontribute pages 6-9).

5) Recent developments (prioritized 2023–2024)

5.1 2024: RidA contributes to competitive fitness and isoleucine flux in E. coli

A 2024 study (Fulton et al., Oct 2024, Microbial Cell, DOI: 10.15698/mic2024.10.837, URL: https://doi.org/10.15698/mic2024.10.837) used coculture experiments to expose subtle phenotypes. It concludes that RidA contributes to fitness in both S. enterica and E. coli, and presents evidence in E. coli for a role in moderating flux toward isoleucine biosynthesis while reducing 2AA stress (fulton2024ridaproteinscontribute pages 1-3).

Quantitatively, the same study reports E. coli IlvE (branched-chain aminotransferase) activity measurements showing little difference among wild type and mutants under some tested conditions (nmol 2KMV/mg protein): WT 130 ± 6, ridA 140 ± 20, tdcF 163 ± 15, ridA tdcF 131 ± 9 in minimal medium; in minimal + serine (5 mM), WT 132 ± 4 vs ridA 110 ± 4 (fulton2024ridaproteinscontribute pages 6-9, fulton2024ridaproteinscontribute media 9bffa396). The study emphasizes that fitness defects can occur even when canonical biochemical damage readouts are subtle in E. coli (fulton2024ridaproteinscontribute pages 3-6, fulton2024ridaproteinscontribute pages 6-9).

5.2 2024: RidA as a practical tool in metabolic engineering

A 2024 metabolic engineering study (Nie et al., Jan 2024, Microbial Cell Factories, DOI: 10.1186/s12934-023-02282-0, URL: https://doi.org/10.1186/s12934-023-02282-0) implemented ridA overexpression in E. coli to improve a synthetic bioconversion route to phenylpyruvate (and then L-phenylalanine).

Key quantitative outcomes:
- With ridA overexpression, phenylpyruvate titer reached 5.0 g/L (30.1 mM) within 24 h.
- Conversion of benzaldehyde → phenylpyruvate increased to 77%.
- The authors report ridA overexpression improved phenylpyruvate production by 16.3%.
(nie2024systematicengineeringenables pages 4-6)

These results support a real-world implementation where RidA is used as a “metabolite stress relief” component in engineered pathways containing PLP enzymes and reactive imine/enamine intermediates (nie2024systematicengineeringenables pages 4-6).

6) Expert opinions and authoritative synthesis

Authoritative reviews emphasize that RidA’s function was difficult to establish because (i) the key substrate is short-lived, (ii) the reaction can occur spontaneously, and (iii) phenotypes are often conditional and depend on metabolic network architecture. Nonetheless, the current expert consensus is that RidA proteins are broadly conserved enamine/imine deaminases whose dominant role is preventing damage by reactive enamines/imines (especially 2AA) and thereby maintaining metabolic robustness (irons2020ridaproteinsprotect pages 5-7, irons2020ridaproteinsprotect pages 8-9).

7) Statistics and data highlights (recent + foundational)

• 2AA half-life ~1.5 s (a key parameter explaining measurement challenges) (irons2020ridaproteinsprotect pages 22-23).
• RidA boosts observed keto-acid production rates from IlvA-derived intermediates by ~2-fold at physiological pH (and higher at alkaline pH in vitro), supporting catalytic quenching beyond spontaneous hydrolysis (irons2020ridaproteinsprotect pages 5-7).
• E. coli IlvE activity values show subtle or condition-dependent differences among ridA/tdcF genotypes in 2024 experiments (fulton2024ridaproteinscontribute pages 6-9, fulton2024ridaproteinscontribute media 9bffa396).
• In metabolic engineering, ridA overexpression yielded 5.0 g/L phenylpyruvate and 77% conversion, with a 16.3% improvement versus without ridA in that system (nie2024systematicengineeringenables pages 4-6).

8) Visual evidence (from 2024 E. coli study)

Table 1 and key fitness results are shown in cropped regions from Fulton et al. 2024, including IlvE activity measurements and competitive fitness/growth phenotypes of E. coli ridA/tdcF mutants under serine perturbation (fulton2024ridaproteinscontribute media 9bffa396, fulton2024ridaproteinscontribute media 552ca70b, fulton2024ridaproteinscontribute media 650e91a4).

9) Concise functional annotation statement (recommended)

ridA (yjgF) encodes a cytosolic, homotrimeric RidA-family enamine/imine deaminase that quenches reactive enamine/imine intermediates (notably 2-aminoacrylate/2-iminopropanoate from serine and 2-aminocrotonate from threonine, generated by IlvA), converting them to stable keto acids (pyruvate or 2-ketobutyrate) and ammonia. This activity protects PLP-dependent enzymes from 2AA-mediated inactivation and supports metabolic robustness and competitive fitness in E. coli, with recent evidence indicating partial redundancy with TdcF and utility in engineered bioproduction pathways. (irons2020ridaproteinsprotect pages 5-7, irons2020ridaproteinsprotect pages 7-8, fulton2024ridaproteinscontribute pages 3-6, nie2024systematicengineeringenables pages 4-6)

Summary table

Table: This table summarizes the core functional annotation of E. coli K-12 RidA/YjgF (UniProt P0AF93), emphasizing biochemical function, physiological role, active-site features, localization, phenotypes, and engineering relevance. It integrates foundational and recent evidence, including quantitative results from 2024 studies.

References

1. (irons2020ridaproteinsprotect pages 5-7): Jessica L. Irons, Kelsey Hodge-Hanson, and Diana M. Downs. Rida proteins protect against metabolic damage by reactive intermediates. Aug 2020. URL: https://doi.org/10.1128/mmbr.00024-20, doi:10.1128/mmbr.00024-20. This article has 52 citations and is from a domain leading peer-reviewed journal.

2. (irons2020ridaproteinsprotect pages 7-8): Jessica L. Irons, Kelsey Hodge-Hanson, and Diana M. Downs. Rida proteins protect against metabolic damage by reactive intermediates. Aug 2020. URL: https://doi.org/10.1128/mmbr.00024-20, doi:10.1128/mmbr.00024-20. This article has 52 citations and is from a domain leading peer-reviewed journal.

3. (fulton2024ridaproteinscontribute pages 1-3): Ronnie L. Fulton, Bryce R. Sawyer, and Diana M Downs. Rida proteins contribute to fitness of s. enterica and e. coli by reducing 2aa stress and moderating flux to isoleucine biosynthesis. Microbial cell, 11:339-352, Oct 2024. URL: https://doi.org/10.15698/mic2024.10.837, doi:10.15698/mic2024.10.837. This article has 1 citations.

4. (irons2020ridaproteinsprotect pages 8-9): Jessica L. Irons, Kelsey Hodge-Hanson, and Diana M. Downs. Rida proteins protect against metabolic damage by reactive intermediates. Aug 2020. URL: https://doi.org/10.1128/mmbr.00024-20, doi:10.1128/mmbr.00024-20. This article has 52 citations and is from a domain leading peer-reviewed journal.

5. (irons2020ridaproteinsprotect pages 22-23): Jessica L. Irons, Kelsey Hodge-Hanson, and Diana M. Downs. Rida proteins protect against metabolic damage by reactive intermediates. Aug 2020. URL: https://doi.org/10.1128/mmbr.00024-20, doi:10.1128/mmbr.00024-20. This article has 52 citations and is from a domain leading peer-reviewed journal.

6. (fulton2025maintainingarobust pages 23-27): RL Fulton. Maintaining a robust and efficient metabolism: fitness contributions by members of the rid protein superfamily. Unknown journal, 2025.

7. (fulton2024ridaproteinscontribute pages 3-6): Ronnie L. Fulton, Bryce R. Sawyer, and Diana M Downs. Rida proteins contribute to fitness of s. enterica and e. coli by reducing 2aa stress and moderating flux to isoleucine biosynthesis. Microbial cell, 11:339-352, Oct 2024. URL: https://doi.org/10.15698/mic2024.10.837, doi:10.15698/mic2024.10.837. This article has 1 citations.

8. (fulton2024ridaproteinscontribute pages 6-9): Ronnie L. Fulton, Bryce R. Sawyer, and Diana M Downs. Rida proteins contribute to fitness of s. enterica and e. coli by reducing 2aa stress and moderating flux to isoleucine biosynthesis. Microbial cell, 11:339-352, Oct 2024. URL: https://doi.org/10.15698/mic2024.10.837, doi:10.15698/mic2024.10.837. This article has 1 citations.

9. (fulton2024ridaproteinscontribute media 9bffa396): Ronnie L. Fulton, Bryce R. Sawyer, and Diana M Downs. Rida proteins contribute to fitness of s. enterica and e. coli by reducing 2aa stress and moderating flux to isoleucine biosynthesis. Microbial cell, 11:339-352, Oct 2024. URL: https://doi.org/10.15698/mic2024.10.837, doi:10.15698/mic2024.10.837. This article has 1 citations.

10. (nie2024systematicengineeringenables pages 4-6): Mengzhen Nie, Jingyu Wang, Zeyao Chen, Chenkai Cao, and Kechun Zhang. Systematic engineering enables efficient biosynthesis of l-phenylalanine in e. coli from inexpensive aromatic precursors. Microbial Cell Factories, Jan 2024. URL: https://doi.org/10.1186/s12934-023-02282-0, doi:10.1186/s12934-023-02282-0. This article has 7 citations and is from a peer-reviewed journal.

11. (fulton2024ridaproteinscontribute media 552ca70b): Ronnie L. Fulton, Bryce R. Sawyer, and Diana M Downs. Rida proteins contribute to fitness of s. enterica and e. coli by reducing 2aa stress and moderating flux to isoleucine biosynthesis. Microbial cell, 11:339-352, Oct 2024. URL: https://doi.org/10.15698/mic2024.10.837, doi:10.15698/mic2024.10.837. This article has 1 citations.

12. (fulton2024ridaproteinscontribute media 650e91a4): Ronnie L. Fulton, Bryce R. Sawyer, and Diana M Downs. Rida proteins contribute to fitness of s. enterica and e. coli by reducing 2aa stress and moderating flux to isoleucine biosynthesis. Microbial cell, 11:339-352, Oct 2024. URL: https://doi.org/10.15698/mic2024.10.837, doi:10.15698/mic2024.10.837. This article has 1 citations.

Citations

1. irons2020ridaproteinsprotect pages 5-7
2. irons2020ridaproteinsprotect pages 22-23
3. fulton2024ridaproteinscontribute pages 1-3
4. nie2024systematicengineeringenables pages 4-6
5. irons2020ridaproteinsprotect pages 7-8
6. irons2020ridaproteinsprotect pages 8-9
7. fulton2025maintainingarobust pages 23-27
8. fulton2024ridaproteinscontribute pages 3-6
9. fulton2024ridaproteinscontribute pages 6-9
10. https://doi.org/10.15698/mic2024.10.837
11. https://doi.org/10.1186/s12934-023-02282-0
12. https://doi.org/10.1128/mmbr.00024-20,
13. https://doi.org/10.15698/mic2024.10.837,
14. https://doi.org/10.1186/s12934-023-02282-0,

BioReason-Pro RL Review: RidA (E. coli)

Source: RidA-deep-research-bioreason-rl.md

• Correctness: 3/5
• Completeness: 3/5

Functional Summary Review

The BioReason functional summary describes RidA as:

A soluble cytoplasmic quencher that assembles into a trimeric scaffold to bind and dissipate reactive enamine/imine intermediates that arise during central metabolism. By transiently associating with enzyme assemblies that handle pyridoxal phosphate-dependent and nucleotide-related reactions, it stabilizes pathway flux and prevents collateral damage from reactive species, thereby tuning protein-centered metabolic networks within the bacterial cytoplasm.

The summary captures the general essence of RidA's function: it is indeed a cytoplasmic homotrimer that processes reactive enamine/imine intermediates. The connection to PLP-dependent enzymes is correctly made. However, there are issues:

1. Molecular function mischaracterization: The thinking trace infers "protein binding" (GO:0005515) as the primary molecular function, claiming the trimeric fold "relies on protein-protein contacts." In reality, RidA is an enzyme -- a 2-iminobutanoate/2-iminopropanoate deaminase (EC 3.5.99.10) -- that catalyzes the hydrolytic release of ammonia from reactive enamine/imine intermediates. The curated review assigns GO:0120241 (2-iminobutanoate/2-iminopropanoate deaminase activity) as the core molecular function.

2. The summary calls RidA a "non-enzymatic yet catalytic chaperone-like module" in the thinking trace, which is contradictory and incorrect. RidA has clear deaminase catalytic activity.

3. Missing pathway specificity: The summary mentions generic "central metabolism" but does not identify the specific pathway -- isoleucine biosynthesis via threonine dehydratase (IlvA) -- which is RidA's primary physiological context.

4. Missing moonlighting function: Under HOCl stress, RidA acquires chaperone holdase activity via N-chlorination of lysine and arginine residues (PMID:25517874). This conditional chaperone function is not mentioned.

The cytoplasmic localization and trimeric assembly are correctly identified.

Comparison with interpro2go:

RidA has no GO_REF:0000002 annotations in the curated review. BioReason's GO predictions include deaminase activity (GO:0019239) and branched-chain amino acid biosynthetic process (GO:0009082), which are accurate and align well with the curated review. Interestingly, the GO predictions are more accurate than the functional summary narrative, which underplays the enzymatic nature. The narrative and GO predictions appear somewhat disconnected.

Notes on thinking trace

The trace correctly identifies all four InterPro domains (RutC-like superfamily, RidA family, YjgF/YER057c/UK114 family, RidA conserved site). However, it then mischaracterizes RidA as "non-enzymatic" despite the RidA family being a well-established enzyme family. The mention of "radical S-adenosylmethionine-dependent enzymes" as interaction partners has no experimental support for RidA.