AprA is the alpha (catalytic) subunit of adenylylsulfate (APS) reductase (EC 1.8.99.2), the central enzyme in dissimilatory sulfate reduction. AprA contains the catalytic FAD cofactor and forms an alpha-beta heterodimer with AprB (the beta subunit containing [4Fe-4S] clusters) to constitute the functional AprAB enzyme. AprAB catalyzes the reduction of adenosine 5'-phosphosulfate (APS) to AMP and sulfite, receiving electrons from the membrane-associated QmoABC complex which connects to the quinone pool. This enzyme sits between ATP sulfurylase (Sat) and dissimilatory sulfite reductase (DsrAB) in the dissimilatory sulfate reduction pathway. AprA is a soluble cytoplasmic protein.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0000104
succinate dehydrogenase activity
|
IEA
GO_REF:0000118 |
REMOVE |
Summary: This annotation is based on TreeGrafter propagation from a PANTHER node (PTN000908678) that encompasses both succinate dehydrogenase and APS reductase family members due to their shared FAD-binding domain architecture. While AprA shares structural homology with succinate dehydrogenase flavoproteins (both belong to the SdhA/FrdA/AprA family IPR030664), AprA catalyzes a completely different reaction. APS reductase (EC 1.8.99.2) catalyzes APS + 2e- + H+ -> AMP + sulfite. This is mechanistically distinct from succinate dehydrogenase activity.
Reason: AprA does not catalyze succinate dehydrogenation. The structural similarity with succinate dehydrogenase flavoproteins (shared FAD-binding domain) does not imply functional equivalence. AprA specifically reduces APS to sulfite and AMP as part of dissimilatory sulfate reduction. This is a clear case of over-annotation from domain-based phylogenetic inference.
Supporting Evidence:
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
APS reductase (EC 1.8.99.2) catalyzes APS + 2e− + H+ → AMP + sulfite (SO3(2−)). The AprA subunit houses the catalytic FAD, while AprB contains iron-sulfur clusters that mediate electron transfer
|
|
GO:0005886
plasma membrane
|
IEA
GO_REF:0000118 |
MODIFY |
Summary: This localization annotation from TreeGrafter is incorrect for AprA. The deep research clearly indicates that AprAB is a soluble cytoplasmic enzyme, functioning in proximity to the cytoplasmic face of the membrane-associated Qmo complex. While AprAB does interact with the membrane-associated QmoABC complex for electron transfer, AprA itself is not membrane-localized.
Reason: AprA is a soluble cytoplasmic protein, not a plasma membrane protein. The TreeGrafter annotation likely propagated from succinate dehydrogenase family members which are membrane-associated. AprA functions in the cytoplasm where it receives electrons from the membrane-associated Qmo complex.
Proposed replacements:
cytoplasm
Supporting Evidence:
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
AprAB is a soluble cytoplasmic enzyme, functioning in proximity to the cytoplasmic face of the membrane-associated Qmo complex that connects to the quinone pool
|
|
GO:0009055
electron transfer activity
|
IEA
GO_REF:0000118 |
MARK AS OVER ANNOTATED |
Summary: This annotation is marginally appropriate but misattributes function within the AprAB complex. The electron transfer function is primarily associated with AprB, which contains the iron-sulfur clusters responsible for shuttling electrons to the catalytic site. AprA contains FAD at the catalytic site and performs the reduction of APS, but does not have the iron-sulfur clusters that mediate electron transfer.
Reason: While AprA participates in an electron-dependent reaction, the electron transfer activity per se is mediated by AprB (with its Fe-S clusters) and the QmoABC complex. AprA's role is catalytic reduction of APS using electrons delivered by AprB. This annotation conflates the catalytic function of AprA with the electron transfer function of its partner subunit.
Supporting Evidence:
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
The AprA subunit houses the catalytic FAD, while AprB contains iron-sulfur clusters that mediate electron transfer, consistent with a flavoprotein-iron–sulfur oxidoreductase mechanism
|
|
GO:0009061
anaerobic respiration
|
IEA
GO_REF:0000118 |
MODIFY |
Summary: This annotation is accurate but insufficiently specific. AprA functions specifically in dissimilatory sulfate reduction, a type of anaerobic respiration where sulfate serves as the terminal electron acceptor. In DvH's dissimilatory sulfate reduction, sulfate is activated by ATP sulfurylase (Sat) to APS, reduced by AprAB to sulfite, and then by dissimilatory sulfite reductase (DsrAB) to sulfide.
Reason: While anaerobic respiration is technically correct, the more specific term GO:0019420 (dissimilatory sulfate reduction) precisely captures AprA's biological role. AprA catalyzes a key step in this pathway where APS is reduced to sulfite.
Proposed replacements:
dissimilatory sulfate reduction
Supporting Evidence:
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
In DvH's dissimilatory sulfate reduction, sulfate is activated by ATP sulfurylase (Sat) to APS, reduced by AprAB to sulfite, and then by dissimilatory sulfite reductase (DsrAB) to sulfide
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
AprA/AprAB sits between Sat (ATP sulfurylase) and DsrAB in the dissimilatory sulfate reduction chain, central to energy metabolism in DvH
|
|
GO:0050660
flavin adenine dinucleotide binding
|
IEA
GO_REF:0000118 |
ACCEPT |
Summary: This annotation is accurate. AprA contains a FAD cofactor that is essential for its catalytic function. UniProt lists FAD as a cofactor (ChEBI:57692), and the deep research confirms that AprA contains the catalytic FAD. The protein has a FAD-binding domain (IPR003953, Pfam:PF00890).
Reason: FAD binding is well-established for AprA based on domain architecture (FAD-binding_2 domain) and functional characterization. The FAD cofactor is central to the catalytic mechanism of APS reduction.
Supporting Evidence:
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
The AprA subunit houses the catalytic FAD
|
|
GO:0009973
adenylyl-sulfate reductase activity
|
IEA
GO_REF:0000003 |
ACCEPT |
Summary: This is the core molecular function of AprA. The annotation is based on EC mapping (EC:1.8.99.2), which is the correct enzyme classification for APS reductase. The deep research extensively supports this: AprA in DvH (DVU_0847; UniProt Q72DT2) encodes the alpha subunit of adenylyl-sulfate (APS) reductase. APS reductase (EC 1.8.99.2) catalyzes APS + 2e- + H+ -> AMP + sulfite.
Reason: This is the primary molecular function of AprA, strongly supported by multiple lines of evidence including EC classification, domain architecture (IPR011803 AprA, TIGR02061), UniProt annotation, and extensive literature.
Supporting Evidence:
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
AprA is the alpha subunit of APS reductase (AprAB). Together with AprB, it catalyzes reduction of APS to sulfite and AMP; AprA contains the catalytic FAD cofactor
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
In DvH proteomics, AprA is explicitly mapped to DVU_0847, confirming the gene-protein assignment in this organism
|
|
GO:0016491
oxidoreductase activity
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: This annotation is accurate but represents a very general parent term. AprA is indeed an oxidoreductase (catalyzing the reduction of APS), and this annotation is derived from InterPro domain mapping (IPR037099) and the oxidoreductase UniProt keyword. However, the more specific term GO:0009973 (adenylyl-sulfate reductase activity) is already present and is more informative.
Reason: While accurate, this is a high-level parent term that is redundant with the more specific GO:0009973. The annotation is technically correct based on the catalytic function of AprA in reducing APS.
Supporting Evidence:
file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
APS reductase (EC 1.8.99.2) catalyzes APS + 2e− + H+ → AMP + sulfite (SO3(2−))
|
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template_variables:
organism: DESVH
gene_id: Q72DT2
gene_symbol: aprA
uniprot_accession: Q72DT2
protein_description: 'SubName: Full=Adenylyl-sulphate reductase, alpha subunit {ECO:0000313|EMBL:AAS95327.1};
EC=1.8.99.2 {ECO:0000313|EMBL:AAS95327.1};'
gene_info: Name=aprA {ECO:0000313|EMBL:AAS95327.1}; OrderedLocusNames=DVU_0847 {ECO:0000313|EMBL:AAS95327.1};
organism_full: Nitratidesulfovibrio vulgaris (strain ATCC 29579 / DSM 644 / CCUG
34227 / NCIMB 8303 / VKM B-1760 / Hildenborough) (Desulfovibrio vulgaris).
protein_family: Not specified in UniProt
protein_domains: AprA. (IPR011803); FAD-dep_OxRdtase_2_FAD-bd. (IPR003953); FAD/NAD-bd_sf.
(IPR036188); Fum_R/Succ_DH_flav-like_C_sf. (IPR037099); SdhA/FrdA/AprA. (IPR030664)
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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 'aprA' 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 aprA (gene ID: Q72DT2, UniProt: Q72DT2) in DESVH.
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 'aprA' 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 aprA (gene ID: Q72DT2, UniProt: Q72DT2) in DESVH.
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
- Objective 1 (verification): Confirm the identity of aprA (DVU_0847; UniProt Q72DT2) from Desulfovibrio vulgaris Hildenborough (DvH), its enzyme class, domains, complex membership (AprAB), and pathway context. (Completed using sources below.) (barton2014hydrogensulfidea pages 16-19, leavitt2019proteomicandisotopic pages 7-9, leavitt2019proteomicandisotopic pages 5-7)
- Objective 2 (recent literature): Prioritize 2023–2024 primary and review literature on APS reductase (AprAB) and the associated Qmo electron transfer system in sulfate reducers. (Completed using 2023 Frontiers RB‑TnSeq study and a 2024 scholarly chapter.) (d’ermo2024thecomplexinterplay pages 5-8, trotter2023largescalegeneticcharacterization pages 4-6)
- Objective 3 (organism-specific evidence): Extract DvH-specific locus, genetic/operon context, essentiality/fitness, proteomics expression, and interaction with Qmo. (Completed from DvH-focused proteomics and RB‑TnSeq datasets.) (leavitt2019proteomicandisotopic pages 7-9, trotter2023largescalegeneticcharacterization pages 4-6, leavitt2019proteomicandisotopic pages 5-7)
- Objective 4 (synthesis): Organize key concepts/definitions, reaction chemistry, cofactors, localization, pathway integration, real-world implications, expert viewpoints, and any available quantitative data. (Completed.) (barton2014hydrogensulfidea pages 16-19, d’ermo2024thecomplexinterplay pages 5-8, barton2014hydrogensulfidea pages 4-7)
- Objective 5 (final report): Write a comprehensive, fully cited research report with URLs and publication dates. (Completed.)
Comprehensive Research Report: aprA (DVU_0847; UniProt Q72DT2) of Desulfovibrio vulgaris Hildenborough
1) Key concepts and definitions with current understanding
- Target verification and identity: The gene aprA in DvH (ordered locus DVU_0847; UniProt Q72DT2) encodes the alpha subunit of adenylyl-sulfate (adenosine-5′-phosphosulfate, APS) reductase, the central enzyme in dissimilatory sulfate reduction that reduces APS to sulfite and AMP; it functions as a heterodimer with AprB (beta subunit) to form APS reductase (AprAB). In Desulfovibrio and other sulfate-reducing bacteria (SRB), AprAB is the canonical enzyme for this step in energy metabolism, distinguishing it from the assimilatory pathway variants. In DvH proteomics, AprA is explicitly mapped to DVU_0847, confirming the gene-protein assignment in this organism. (Barton et al., 2014; Leavitt et al., 2019) https://doi.org/10.1007/978-94-017-9269-1_10; https://doi.org/10.3389/fmicb.2019.00658 (barton2014hydrogensulfidea pages 16-19, leavitt2019proteomicandisotopic pages 7-9, leavitt2019proteomicandisotopic pages 5-7)
- Enzyme class and reaction: APS reductase (EC 1.8.99.2) catalyzes APS + 2e− + H+ → AMP + sulfite (SO3(2−)). The AprA subunit houses the catalytic FAD, while AprB contains iron-sulfur clusters that mediate electron transfer, consistent with a flavoprotein-iron–sulfur oxidoreductase mechanism. (Barton et al., 2014) https://doi.org/10.1007/978-94-017-9269-1_10 (barton2014hydrogensulfidea pages 16-19)
- Electron donor system and complex association: Electron delivery to AprAB is mediated by the membrane-associated Qmo (quinone-interacting membrane-bound oxidoreductase) complex (QmoABC), which couples quinone pool redox chemistry to APS reduction; genomic co-localization of aprAB with qmoABC is common in SRB and functionally linked to APS reduction. (Barton et al., 2014; D’Ermo et al., 2024; Saxena et al., 2023) https://doi.org/10.1007/978-94-017-9269-1_10; https://doi.org/10.1007/978-3-031-54306-7_15; https://doi.org/10.3389/fmicb.2023.1086021 (barton2014hydrogensulfidea pages 16-19, d’ermo2024thecomplexinterplay pages 5-8, saxena2023integrationoftext pages 5-6)
- Pathway context: In DvH’s dissimilatory sulfate reduction, sulfate is activated by ATP sulfurylase (Sat) to APS, reduced by AprAB to sulfite, and then by dissimilatory sulfite reductase (DsrAB) to sulfide, with multiple electron transfer modules (including Qmo and downstream complexes) supporting energy conservation. (Barton et al., 2014; D’Ermo et al., 2024) https://doi.org/10.1007/978-94-017-9269-1_10; https://doi.org/10.1007/978-3-031-54306-7_15 (barton2014hydrogensulfidea pages 16-19, d’ermo2024thecomplexinterplay pages 5-8)
2) Recent developments and latest research (priority to 2023–2024)
- Genome-wide fitness genetics in DvH (2023): A large RB‑TnSeq study in DvH mapped essential and conditionally essential genes across 2,741 loci under diverse conditions, providing a reference for sulfate-reduction gene fitness. Although focused broadly on metabolism, this dataset defines condition dependencies and essential gene sets relevant to sulfate reduction, establishing a contemporary genetic framework that includes the sulfate reduction module (sat/apr/dsr). (Trotter et al., 2023, Frontiers in Microbiology; Mar 2023) https://doi.org/10.3389/fmicb.2023.1095191 (trotter2023largescalegeneticcharacterization pages 4-6)
- Updated mechanistic overview (2024): A 2024 scholarly chapter synthesizes sulfur bioenergetics, reaffirming that Sat→AprAB→DsrAB is the canonical dissimilatory route, with AprAB receiving electrons via Qmo linked to the quinone pool, emphasizing electron-transfer coupling and broader geochemical interplay. This contextualizes AprAB within redox network models that integrate quinone-linked electron flow. (D’Ermo et al., 2024; Jan 2024) https://doi.org/10.1007/978-3-031-54306-7_15 (d’ermo2024thecomplexinterplay pages 5-8)
3) Current applications and real-world implementations
- Biogeochemistry and environmental monitoring: aprA/AprAB are widely used functional markers for detecting and quantifying SRB activity in sediments and subsurface environments, forming part of multi-gene panels with dsrAB and sat to infer sulfate reduction potential and activity. This has implications for interpreting sulfur-coupled carbon transformations and contaminant mobility. (Barton et al., 2014; D’Ermo et al., 2024) https://doi.org/10.1007/978-94-017-9269-1_10; https://doi.org/10.1007/978-3-031-54306-7_15 (barton2014hydrogensulfidea pages 16-19, d’ermo2024thecomplexinterplay pages 5-8)
- Industrial relevance and corrosion: SRB-mediated sulfide generation (to which AprAB is central) underpins souring and microbiologically influenced corrosion problems; understanding AprAB and its regulation within the pathway informs strategies for monitoring and mitigation. (Barton et al., 2014) https://doi.org/10.1007/978-94-017-9269-1_10 (barton2014hydrogensulfidea pages 4-7)
4) Expert opinions and analysis from authoritative sources
- Enzymology and electron transfer architecture: Authoritative review content consolidates the model in which AprA contains the catalytic FAD, AprB contributes Fe–S electron-transfer capacity, and QmoABC serves as the physiological electron donor, linking APS reduction to the quinone pool—placing AprAB at the hub of energy conservation in sulfate respiration. (Barton et al., 2014) https://doi.org/10.1007/978-94-017-9269-1_10 (barton2014hydrogensulfidea pages 16-19)
- Systems perspective on sulfur bioenergetics: Expert synthesis in 2024 situates AprAB’s role within modular redox networks and geochemical cycles, underscoring the coupling between quinone redox chemistry and APS reduction and motivating integrative studies that combine genomics/proteomics with environmental geochemistry. (D’Ermo et al., 2024) https://doi.org/10.1007/978-3-031-54306-7_15 (d’ermo2024thecomplexinterplay pages 5-8)
5) Relevant statistics and data from recent studies
- Proteomics expression in DvH: In a DvH proteomics study testing perturbation of the downstream DsrC component, AprA (DVU_0847) abundance decreased in the mutant relative to wild type (−0.35 ± 0.21), and the associated QmoB (DVU_0849) also decreased (−0.52 ± 0.27), consistent with coordinated regulation and functional linkage in the sulfate-reduction chain. (Leavitt et al., 2019; Apr 2019) https://doi.org/10.3389/fmicb.2019.00658 (leavitt2019proteomicandisotopic pages 7-9, leavitt2019proteomicandisotopic pages 5-7)
- Genome-wide fitness framework in DvH: RB‑TnSeq across 2,741 protein-coding genes identified extensive conditional phenotypes and essentiality patterns, delineating a modern genetic map for DvH metabolism that includes sulfate-reduction modules, which can be used to frame hypotheses about aprA essentiality under sulfate-respiring conditions. (Trotter et al., 2023; Mar 2023) https://doi.org/10.3389/fmicb.2023.1095191 (trotter2023largescalegeneticcharacterization pages 4-6)
Functional annotation for aprA (DVU_0847; Q72DT2) in DvH
- Primary function and reaction: AprA is the alpha subunit of APS reductase (AprAB). Together with AprB, it catalyzes reduction of APS to sulfite and AMP; AprA contains the catalytic FAD cofactor, while AprB houses [4Fe–4S] clusters for electron transfer. Substrate: APS; products: sulfite + AMP. (Barton et al., 2014) https://doi.org/10.1007/978-94-017-9269-1_10 (barton2014hydrogensulfidea pages 16-19)
- Subunit composition and cofactors: AprAB is an αβ heterodimer. AprA (FAD-binding flavoenzyme); AprB (Fe–S protein). These features align with UniProt domain annotations (FAD/NAD-binding and succinate dehydrogenase–like flavoprotein folds). (Barton et al., 2014) https://doi.org/10.1007/978-94-017-9269-1_10 (barton2014hydrogensulfidea pages 16-19)
- Electron donor system: Physiological electrons are delivered from the membrane quinone pool via the QmoABC complex to AprAB, consistent with aprAB–qmoABC genomic linkage and coordinated protein abundance. (Barton et al., 2014; D’Ermo et al., 2024; Leavitt et al., 2019) https://doi.org/10.1007/978-94-017-9269-1_10; https://doi.org/10.1007/978-3-031-54306-7_15; https://doi.org/10.3389/fmicb.2019.00658 (barton2014hydrogensulfidea pages 16-19, d’ermo2024thecomplexinterplay pages 5-8, leavitt2019proteomicandisotopic pages 7-9)
- Genomic context in DvH: In DvH, aprA corresponds to DVU_0847 and is adjacent to qmo genes (e.g., qmoB DVU_0849), supporting an operonic/linkage relationship typical for SRB sulfate-reduction loci. (Leavitt et al., 2019) https://doi.org/10.3389/fmicb.2019.00658 (leavitt2019proteomicandisotopic pages 7-9)
- Cellular localization: AprAB is a soluble cytoplasmic enzyme, functioning in proximity to the cytoplasmic face of the membrane-associated Qmo complex that connects to the quinone pool. (Barton et al., 2014) https://doi.org/10.1007/978-94-017-9269-1_10 (barton2014hydrogensulfidea pages 16-19)
- Pathway integration: AprA/AprAB sits between Sat (ATP sulfurylase) and DsrAB in the dissimilatory sulfate reduction chain, central to energy metabolism in DvH. (D’Ermo et al., 2024; Barton et al., 2014) https://doi.org/10.1007/978-3-031-54306-7_15; https://doi.org/10.1007/978-94-017-9269-1_10 (d’ermo2024thecomplexinterplay pages 5-8, barton2014hydrogensulfidea pages 16-19)
- Organism-specific experimental evidence: DvH proteomics links DVU_0847 (AprA) to decreased abundance under DsrC perturbation, along with decreased QmoB, consistent with coordinated control; RB‑TnSeq in DvH provides a contemporary essentiality/fitness scaffold for sulfate-reduction genes. (Leavitt et al., 2019; Trotter et al., 2023) https://doi.org/10.3389/fmicb.2019.00658; https://doi.org/10.3389/fmicb.2023.1095191 (leavitt2019proteomicandisotopic pages 7-9, trotter2023largescalegeneticcharacterization pages 4-6, leavitt2019proteomicandisotopic pages 5-7)
Ambiguity check
- The symbol aprA can be used broadly across bacteria and archaea for APS reductase alpha subunits. Here, the identity is unambiguous: DVU_0847 in DvH (UniProt Q72DT2), matching the organism Desulfovibrio vulgaris Hildenborough and aligning with canonical AprA domains and the AprAB enzyme system. If literature on other organisms with aprA exists, it was not used to infer divergent functions here. (Leavitt et al., 2019; Barton et al., 2014) https://doi.org/10.3389/fmicb.2019.00658; https://doi.org/10.1007/978-94-017-9269-1_10 (leavitt2019proteomicandisotopic pages 7-9, barton2014hydrogensulfidea pages 16-19)
Limitations and open questions
- While structures and biophysical details of AprAB are well-established in the SRB literature, the most recent organism-specific structural updates for DvH AprAB were not identified in the 2023–2024 window surveyed here. Nevertheless, multiple 2023–2024 sources reaffirm the mechanistic model and genetic context for AprAB/Qmo in sulfate reducers. (D’Ermo et al., 2024; Trotter et al., 2023) https://doi.org/10.1007/978-3-031-54306-7_15; https://doi.org/10.3389/fmicb.2023.1095191 (d’ermo2024thecomplexinterplay pages 5-8, trotter2023largescalegeneticcharacterization pages 4-6)
References
(barton2014hydrogensulfidea pages 16-19): Larry L. Barton, Marie-Laure Fardeau, and Guy D. Fauque. Hydrogen sulfide: a toxic gas produced by dissimilatory sulfate and sulfur reduction and consumed by microbial oxidation. Metal ions in life sciences, 14:237-77, Jan 2014. URL: https://doi.org/10.1007/978-94-017-9269-1_10, doi:10.1007/978-94-017-9269-1_10. This article has 151 citations and is from a peer-reviewed journal.
(leavitt2019proteomicandisotopic pages 7-9): William D. Leavitt, Sofia S. Venceslau, Jacob Waldbauer, Derek A. Smith, Inês A. Cardoso Pereira, and Alexander S. Bradley. Proteomic and isotopic response of desulfovibrio vulgaris to dsrc perturbation. Frontiers in Microbiology, Apr 2019. URL: https://doi.org/10.3389/fmicb.2019.00658, doi:10.3389/fmicb.2019.00658. This article has 12 citations and is from a poor quality or predatory journal.
(leavitt2019proteomicandisotopic pages 5-7): William D. Leavitt, Sofia S. Venceslau, Jacob Waldbauer, Derek A. Smith, Inês A. Cardoso Pereira, and Alexander S. Bradley. Proteomic and isotopic response of desulfovibrio vulgaris to dsrc perturbation. Frontiers in Microbiology, Apr 2019. URL: https://doi.org/10.3389/fmicb.2019.00658, doi:10.3389/fmicb.2019.00658. This article has 12 citations and is from a poor quality or predatory journal.
(d’ermo2024thecomplexinterplay pages 5-8): Giulia D’Ermo, Marianne Guiral, and Barbara Schoepp-Cothenet. The complex interplay of sulfur and arsenic bioenergetic metabolisms in the arsenic geochemical cycle. Geomicrobiology: Natural and Anthropogenic Settings, pages 301-328, Jan 2024. URL: https://doi.org/10.1007/978-3-031-54306-7_15, doi:10.1007/978-3-031-54306-7_15. This article has 1 citations.
(trotter2023largescalegeneticcharacterization pages 4-6): Valentine V. Trotter, Maxim Shatsky, Morgan N. Price, Thomas R. Juba, Grant M. Zane, Kara B. De León, Erica L.-W. Majumder, Qin Gui, Rida Ali, Kelly M. Wetmore, Jennifer V. Kuehl, Adam P. Arkin, Judy D. Wall, Adam M. Deutschbauer, John-Marc Chandonia, and Gareth P. Butland. Large-scale genetic characterization of the model sulfate-reducing bacterium, desulfovibrio vulgaris hildenborough. Frontiers in Microbiology, Mar 2023. URL: https://doi.org/10.3389/fmicb.2023.1095191, doi:10.3389/fmicb.2023.1095191. This article has 11 citations and is from a poor quality or predatory journal.
(barton2014hydrogensulfidea pages 4-7): Larry L. Barton, Marie-Laure Fardeau, and Guy D. Fauque. Hydrogen sulfide: a toxic gas produced by dissimilatory sulfate and sulfur reduction and consumed by microbial oxidation. Metal ions in life sciences, 14:237-77, Jan 2014. URL: https://doi.org/10.1007/978-94-017-9269-1_10, doi:10.1007/978-94-017-9269-1_10. This article has 151 citations and is from a peer-reviewed journal.
(saxena2023integrationoftext pages 5-6): Priya Saxena, Shailabh Rauniyar, Payal Thakur, Ram Nageena Singh, Alain Bomgni, Mathew O. Alaba, Abhilash Kumar Tripathi, Etienne Z. Gnimpieba, Carol Lushbough, and Rajesh Kumar Sani. Integration of text mining and biological network analysis: identification of essential genes in sulfate-reducing bacteria. Frontiers in Microbiology, Apr 2023. URL: https://doi.org/10.3389/fmicb.2023.1086021, doi:10.3389/fmicb.2023.1086021. This article has 14 citations and is from a poor quality or predatory journal.
id: Q72DT2
gene_symbol: aprA
product_type: PROTEIN
status: COMPLETE
taxon:
id: NCBITaxon:882
label: Nitratidesulfovibrio vulgaris (Desulfovibrio vulgaris) Hildenborough
description: >-
AprA is the alpha (catalytic) subunit of adenylylsulfate (APS) reductase (EC 1.8.99.2),
the central enzyme in dissimilatory sulfate reduction. AprA contains the catalytic FAD
cofactor and forms an alpha-beta heterodimer with AprB (the beta subunit containing [4Fe-4S]
clusters) to constitute the functional AprAB enzyme. AprAB catalyzes the reduction of
adenosine 5'-phosphosulfate (APS) to AMP and sulfite, receiving electrons from the
membrane-associated QmoABC complex which connects to the quinone pool. This enzyme sits
between ATP sulfurylase (Sat) and dissimilatory sulfite reductase (DsrAB) in the
dissimilatory sulfate reduction pathway. AprA is a soluble cytoplasmic protein.
existing_annotations:
- term:
id: GO:0000104
label: succinate dehydrogenase activity
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: >-
This annotation is based on TreeGrafter propagation from a PANTHER node
(PTN000908678) that encompasses both succinate dehydrogenase and APS reductase
family members due to their shared FAD-binding domain architecture. While AprA
shares structural homology with succinate dehydrogenase flavoproteins (both belong
to the SdhA/FrdA/AprA family IPR030664), AprA catalyzes a completely different
reaction. APS reductase (EC 1.8.99.2) catalyzes APS + 2e- + H+ -> AMP + sulfite.
This is mechanistically distinct from succinate dehydrogenase activity.
action: REMOVE
reason: >-
AprA does not catalyze succinate dehydrogenation. The structural similarity with
succinate dehydrogenase flavoproteins (shared FAD-binding domain) does not imply
functional equivalence. AprA specifically reduces APS to sulfite and AMP as part
of dissimilatory sulfate reduction. This is a clear case of over-annotation from
domain-based phylogenetic inference.
supported_by:
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "APS reductase (EC 1.8.99.2) catalyzes APS + 2e− + H+ → AMP + sulfite (SO3(2−)). The AprA subunit houses the catalytic FAD, while AprB contains iron-sulfur clusters that mediate electron transfer"
- term:
id: GO:0005886
label: plasma membrane
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: >-
This localization annotation from TreeGrafter is incorrect for AprA. The deep
research clearly indicates that AprAB is a soluble cytoplasmic enzyme, functioning
in proximity to the cytoplasmic face of the membrane-associated Qmo complex.
While AprAB does interact with the membrane-associated QmoABC complex for electron
transfer, AprA itself is not membrane-localized.
action: MODIFY
reason: >-
AprA is a soluble cytoplasmic protein, not a plasma membrane protein. The
TreeGrafter annotation likely propagated from succinate dehydrogenase family
members which are membrane-associated. AprA functions in the cytoplasm where it
receives electrons from the membrane-associated Qmo complex.
proposed_replacement_terms:
- id: GO:0005737
label: cytoplasm
supported_by:
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "AprAB is a soluble cytoplasmic enzyme, functioning in proximity to the cytoplasmic face of the membrane-associated Qmo complex that connects to the quinone pool"
- term:
id: GO:0009055
label: electron transfer activity
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: >-
This annotation is marginally appropriate but misattributes function within the
AprAB complex. The electron transfer function is primarily associated with AprB,
which contains the iron-sulfur clusters responsible for shuttling electrons to the
catalytic site. AprA contains FAD at the catalytic site and performs the reduction
of APS, but does not have the iron-sulfur clusters that mediate electron transfer.
action: MARK_AS_OVER_ANNOTATED
reason: >-
While AprA participates in an electron-dependent reaction, the electron transfer
activity per se is mediated by AprB (with its Fe-S clusters) and the QmoABC
complex. AprA's role is catalytic reduction of APS using electrons delivered by
AprB. This annotation conflates the catalytic function of AprA with the electron
transfer function of its partner subunit.
supported_by:
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "The AprA subunit houses the catalytic FAD, while AprB contains iron-sulfur clusters that mediate electron transfer, consistent with a flavoprotein-iron–sulfur oxidoreductase mechanism"
- term:
id: GO:0009061
label: anaerobic respiration
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: >-
This annotation is accurate but insufficiently specific. AprA functions specifically
in dissimilatory sulfate reduction, a type of anaerobic respiration where sulfate
serves as the terminal electron acceptor. In DvH's dissimilatory sulfate reduction,
sulfate is activated by ATP sulfurylase (Sat) to APS, reduced by AprAB to sulfite,
and then by dissimilatory sulfite reductase (DsrAB) to sulfide.
action: MODIFY
reason: >-
While anaerobic respiration is technically correct, the more specific term
GO:0019420 (dissimilatory sulfate reduction) precisely captures AprA's biological
role. AprA catalyzes a key step in this pathway where APS is reduced to sulfite.
proposed_replacement_terms:
- id: GO:0019420
label: dissimilatory sulfate reduction
supported_by:
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "In DvH's dissimilatory sulfate reduction, sulfate is activated by ATP sulfurylase (Sat) to APS, reduced by AprAB to sulfite, and then by dissimilatory sulfite reductase (DsrAB) to sulfide"
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "AprA/AprAB sits between Sat (ATP sulfurylase) and DsrAB in the dissimilatory sulfate reduction chain, central to energy metabolism in DvH"
- term:
id: GO:0050660
label: flavin adenine dinucleotide binding
evidence_type: IEA
original_reference_id: GO_REF:0000118
review:
summary: >-
This annotation is accurate. AprA contains a FAD cofactor that is essential for
its catalytic function. UniProt lists FAD as a cofactor (ChEBI:57692), and the
deep research confirms that AprA contains the catalytic FAD. The protein has a
FAD-binding domain (IPR003953, Pfam:PF00890).
action: ACCEPT
reason: >-
FAD binding is well-established for AprA based on domain architecture (FAD-binding_2
domain) and functional characterization. The FAD cofactor is central to the
catalytic mechanism of APS reduction.
supported_by:
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "The AprA subunit houses the catalytic FAD"
- term:
id: GO:0009973
label: adenylyl-sulfate reductase activity
evidence_type: IEA
original_reference_id: GO_REF:0000003
review:
summary: >-
This is the core molecular function of AprA. The annotation is based on EC mapping
(EC:1.8.99.2), which is the correct enzyme classification for APS reductase. The
deep research extensively supports this: AprA in DvH (DVU_0847; UniProt Q72DT2)
encodes the alpha subunit of adenylyl-sulfate (APS) reductase. APS reductase
(EC 1.8.99.2) catalyzes APS + 2e- + H+ -> AMP + sulfite.
action: ACCEPT
reason: >-
This is the primary molecular function of AprA, strongly supported by multiple
lines of evidence including EC classification, domain architecture (IPR011803
AprA, TIGR02061), UniProt annotation, and extensive literature.
supported_by:
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "AprA is the alpha subunit of APS reductase (AprAB). Together with AprB, it catalyzes reduction of APS to sulfite and AMP; AprA contains the catalytic FAD cofactor"
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "In DvH proteomics, AprA is explicitly mapped to DVU_0847, confirming the gene-protein assignment in this organism"
- term:
id: GO:0016491
label: oxidoreductase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: >-
This annotation is accurate but represents a very general parent term. AprA is
indeed an oxidoreductase (catalyzing the reduction of APS), and this annotation
is derived from InterPro domain mapping (IPR037099) and the oxidoreductase UniProt
keyword. However, the more specific term GO:0009973 (adenylyl-sulfate reductase
activity) is already present and is more informative.
action: ACCEPT
reason: >-
While accurate, this is a high-level parent term that is redundant with the more
specific GO:0009973. The annotation is technically correct based on the catalytic
function of AprA in reducing APS.
supported_by:
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "APS reductase (EC 1.8.99.2) catalyzes APS + 2e− + H+ → AMP + sulfite (SO3(2−))"
references:
- id: GO_REF:0000003
title: Gene Ontology annotation based on Enzyme Commission mapping
findings:
- statement: Maps EC:1.8.99.2 to GO:0009973 (adenylyl-sulfate reductase activity)
- id: GO_REF:0000118
title: TreeGrafter-generated GO annotations
findings:
- statement: Propagated annotations from PANTHER node PTN000908678 (succinate dehydrogenase family)
- statement: Some propagated annotations are incorrect for AprA due to functional divergence within the family
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings:
- statement: Derived oxidoreductase activity from InterPro domain IPR037099
- id: PMID:25416397
title: "Hydrogen sulfide: a toxic gas produced by dissimilatory sulfate and sulfur reduction and consumed by microbial oxidation."
findings:
- statement: Comprehensive review of dissimilatory sulfate reduction enzymology
supporting_text: "This review provides an examination of cytochromes, iron-sulfur proteins, and sirohemes participating in electron movement in diverse groups of sulfate-reducing, sulfur-reducing, and sulfide-oxidizing Bacteria and Archaea"
- statement: Review of enzymatic activities in sulfate reduction
supporting_text: "biosulfur reduction or oxidation requires unique enzymatic activities with metal cofactors participating in electron transfer"
- id: PMID:31031715
title: "Proteomic and Isotopic Response of Desulfovibrio vulgaris to DsrC Perturbation."
findings:
- statement: DvH proteomics maps AprA to DVU0847 with expression data
supporting_text: "The APS reductase subunit AprA (DVU0847) showed lower relative expression in the mutant"
- statement: Shows coordinated regulation of AprA and QmoB
supporting_text: "The APS reductase subunit AprA (DVU0847) showed lower relative expression in the mutant (–0.35 ± 0.21), as did a subunit, QmoB (DVU0849), of its affiliated electron donor complex"
- id: PMID:37065130
title: "Large-scale genetic characterization of the model sulfate-reducing bacterium, Desulfovibrio vulgaris Hildenborough."
findings:
- statement: RB-TnSeq study providing fitness data for DvH genes
supporting_text: "we generated a randomly barcoded transposon mutant library in the model SRB Desulfovibrio vulgaris Hildenborough (DvH) and used this genome-wide resource to assay the importance of its genes"
- statement: Framework for understanding essentiality of sulfate reduction genes
supporting_text: "In addition to defining the essential gene set of DvH, we identified a conditional phenotype for 1,137 non-essential genes"
- id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
title: Deep research synthesis for aprA (Q72DT2)
findings:
- statement: Synthesis of literature on AprA function in dissimilatory sulfate reduction
- statement: Confirms AprAB is soluble cytoplasmic enzyme with FAD cofactor in AprA
core_functions:
- description: >-
AprA is the alpha subunit of APS reductase (EC 1.8.99.2), catalyzing the
reduction of adenosine 5'-phosphosulfate (APS) to AMP and sulfite. This is
the defining enzymatic function of the protein, supported by EC classification,
domain architecture (IPR011803, TIGR02061), and extensive biochemical
characterization in the literature. AprA contains a FAD cofactor essential
for catalysis. AprAB is a soluble cytoplasmic enzyme.
molecular_function:
id: GO:0009973
label: adenylyl-sulfate reductase activity
directly_involved_in:
- id: GO:0019420
label: dissimilatory sulfate reduction
locations:
- id: GO:0005737
label: cytoplasm
supported_by:
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "AprA is the alpha subunit of APS reductase (AprAB). Together with AprB, it catalyzes reduction of APS to sulfite and AMP; AprA contains the catalytic FAD cofactor"
- reference_id: file:DESVH/Q72DT2/Q72DT2-deep-research-falcon.md
supporting_text: "AprAB is a soluble cytoplasmic enzyme, functioning in proximity to the cytoplasmic face of the membrane-associated Qmo complex that connects to the quinone pool"