PP_0635 encodes a bacterial reverse transcriptase (RT) belonging to the group II intron maturase family. The protein contains characteristic domains including Group_II_RT_mat (IPR030931), Mat_intron_G2 (IPR013597), and GrpII_Intron_Splice-Mob/Def (IPR051083). Based on genomic context analysis, the KT2440 genome harbors group II introns within genomic islands, and PP_0635 most plausibly functions as a group II intron-encoded RT/maturase involved in intron RNA folding, splicing, and retrohoming/retrotransposition. There is no direct evidence that this protein functions as a retron RT or participates in phage defense; the group II intron context is more likely based on domain architecture and genomic organization.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
|
GO:0003723
RNA binding
|
IEA
GO_REF:0000002 |
ACCEPT |
Summary: This annotation is inferred from InterPro domain mapping. Group II intron maturases are known to bind their cognate intron RNA to promote correct folding and splicing. The domain architecture (Group_II_RT_mat, Mat_intron_G2) is consistent with RNA binding activity as part of the maturase function.
Reason: Group II intron RT/maturases bind specifically to their intron RNA as part of ribonucleoprotein (RNP) assembly. This binding is essential for maturase activity (promoting intron folding and splicing) and for retrohoming/retrotransposition. The annotation is appropriately broad and supported by the domain architecture. [Gapinska et al. 2024, NAR: "group II intron maturases are associated with intron RNA splicing/mobility"]
Supporting Evidence:
DOI:10.1093/nar/gkae230
group II intron maturases are associated with intron RNA splicing/mobility
|
|
GO:0003964
RNA-directed DNA polymerase activity
|
IEA
GO_REF:0000120 |
ACCEPT |
Summary: This is the core enzymatic activity of reverse transcriptases. PP_0635 is annotated with EC:2.7.7.49 (RNA-directed DNA polymerase) and contains the RT domain (IPR000477, PROSITE PS50878). This activity is fundamental to group II intron RT/maturases for retrohoming.
Reason: The RT domain is clearly present (residues 100-326 per UniProt feature annotation) and the protein belongs to the bacterial reverse transcriptase family. RNA-directed DNA polymerase activity is the defining enzymatic function of group II intron maturases, used during retrohoming/retrotransposition to copy the intron RNA into DNA. [Weinel et al. 2002: "KT2440 genome harbors group II introns"; Gapinska et al. 2024: "Bacterial RTs, including group II intron maturases...display polymerase activity in vitro and in vivo"]
Supporting Evidence:
DOI:10.1046/j.1462-2920.2002.00331.x
KT2440 genome harbors group II introns
DOI:10.1093/nar/gkae230
Bacterial RTs, including group II intron maturases and defense-associated RTs, display polymerase activity in vitro and in vivo
|
|
GO:0006278
RNA-templated DNA biosynthetic process
|
IEA
GO_REF:0000002 |
MODIFY |
Summary: This biological process annotation corresponds to the RNA-directed DNA polymerase activity of the RT. For group II intron maturases, this process is part of retrohoming/retrotransposition where the intron RNA is reverse transcribed into DNA for integration at a new genomic site.
Reason: While the annotation is not incorrect (the protein does perform RNA-templated DNA biosynthesis), a more specific term would better capture the biological context. The RT activity in group II intron maturases specifically functions in retrotransposition/retrohoming of the intron element. GO:0032197 (retrotransposition) or GO:0006315 (homing of group II introns) would be more informative.
Proposed replacements:
homing of group II introns
Group II intron splicing
Supporting Evidence:
DOI:10.1046/j.1462-2920.2002.00331.x
The KT2440 genome contains group II introns within genomic islands
DOI:10.1093/nar/gkae230
group II intron maturases...catalyze reverse transcription during intron mobility (retrohoming)
|
|
GO:0016740
transferase activity
|
IEA
GO_REF:0000043 |
MARK AS OVER ANNOTATED |
Summary: This is a very high-level parent term of the more specific RNA-directed DNA polymerase activity. While technically correct (RT is a nucleotidyltransferase, which is a transferase), this annotation provides minimal information beyond what is already captured by the more specific GO:0003964.
Reason: The annotation is redundant given the presence of the more specific GO:0003964 (RNA-directed DNA polymerase activity). High-level terms like "transferase activity" provide little functional insight when more specific terms are already annotated. This is an artifact of automated keyword-based annotation.
|
|
GO:0016779
nucleotidyltransferase activity
|
IEA
GO_REF:0000043 |
MARK AS OVER ANNOTATED |
Summary: This is a parent term of RNA-directed DNA polymerase activity (GO:0003964). While technically correct, it is redundant when the more specific term is already annotated.
Reason: The annotation is redundant given the presence of the more specific GO:0003964 (RNA-directed DNA polymerase activity). Nucleotidyltransferase activity is a parent term and provides less precise functional information. The more specific RT activity term should be preferred.
|
|
GO:0046872
metal ion binding
|
IEA
GO_REF:0000043 |
ACCEPT |
Summary: Reverse transcriptases require divalent metal ions (typically Mg2+) for catalytic activity. The UniProt annotation includes the keyword "Magnesium" and "Metal-binding". This is a standard requirement for polymerase activity.
Reason: Metal ion binding (specifically Mg2+) is essential for the catalytic mechanism of reverse transcriptases. The polymerase active site coordinates metal ions for nucleotidyl transfer. The UniProt record includes "Magnesium" and "Metal-binding" keywords supporting this annotation.
Supporting Evidence:
UniProt:Q877L4
Magnesium {ECO:0000256|ARBA:ARBA00022842}
|
|
GO:0051607
defense response to virus
|
IEA
GO_REF:0000043 |
REMOVE |
Summary: This annotation is problematic. It was inferred from the UniProt keyword "Antiviral defense" which was itself automatically assigned. While some bacterial RTs DO function in phage defense (retrons, Abi systems, CRISPR-RT), PP_0635 has domain architecture characteristic of group II intron maturases, NOT defense-associated RTs. The deep research explicitly states there is no evidence this protein participates in defense.
Reason: The annotation represents a likely over-annotation based on an overly broad automated rule. Key evidence against a defense function: 1) Domain architecture (Group_II_RT_mat, Mat_intron_G2) is characteristic
of group II intron maturases, not retron or Abi defense RTs
2) The KT2440 genome context shows group II introns in genomic islands,
consistent with mobile genetic element function rather than defense
3) Recent literature (Gapinska 2024) explicitly distinguishes defense RTs
(Abi/retrons) from group II intron maturases by domain architecture
and biological role
4) No retron ncRNA or effector locus has been identified near PP_0635 5) Deep research concluded: "There is no direct evidence that PP_0635 is
a retron RT or participates in a retron defense module"
Supporting Evidence:
DOI:10.1093/nar/gkae230
retron RTs assemble with msDNA and effectors into higher-order anti-phage complexes, while group II intron maturases are associated with intron RNA splicing/mobility
DOI:10.1046/j.1462-2920.2002.00331.x
The KT2440 genome harbors group II introns within genomic islands
file:PSEPK/PP_0635/PP_0635-deep-research-falcon.md
There is no direct evidence that PP_0635 is a retron RT or participates in a retron defense module; the more likely context is group II intron biology within genomic islands of KT2440
|
|
GO:0006315
homing of group II introns
|
ISS
DOI:10.1046/j.1462-2920.2002.00331.x |
NEW |
Summary: Proposed new annotation. Group II intron maturases catalyze retrohoming (lateral transfer of the intron to a homologous allele lacking the intron). The domain architecture and genomic context strongly support this function.
Reason: PP_0635 contains the characteristic domains of group II intron maturases (Group_II_RT_mat IPR030931, Mat_intron_G2 IPR013597) and is located within genomic islands known to contain group II introns in KT2440. The RT activity is used for retrohoming - reverse transcription of the intron RNA followed by integration at a new site.
Supporting Evidence:
DOI:10.1046/j.1462-2920.2002.00331.x
The KT2440 genome harbors group II introns within genomic islands
DOI:10.1093/nar/gkae230
Group II intron RT/maturases typically bind their intron RNA and promote correct folding and splicing, and catalyze reverse transcription during intron mobility (retrohoming)
|
|
GO:0000373
Group II intron splicing
|
ISS
DOI:10.1093/nar/gkae230 |
NEW |
Summary: Proposed new annotation. Group II intron maturases have a second key function beyond RT activity - they act as maturases that promote correct folding and splicing of their cognate intron RNA.
Reason: The maturase domain (Mat_intron_G2 IPR013597, Group_II_RT_mat IPR030931) indicates this protein assists in group II intron splicing by binding the intron RNA and promoting correct folding for the autocatalytic splicing reaction. This is a core function distinct from the RT activity.
Supporting Evidence:
DOI:10.1093/nar/gkae230
Group II intron RT/maturases typically bind their intron RNA and promote correct folding and splicing
|
Q: Is PP_0635 associated with a specific group II intron in the KT2440 genome?
Q: What is the cognate intron RNA for this maturase?
Q: Has the RT activity been experimentally validated?
Q: Are there any experimental studies on intron mobility/retrohoming in P. putida KT2440?
Experiment: Co-immunoprecipitation to identify associated RNAs (cognate intron)
Hypothesis: PP_0635 binds a specific group II intron RNA in the KT2440 genome.
Experiment: RT activity assay with purified protein
Hypothesis: PP_0635 has RNA-directed DNA polymerase activity.
Experiment: Intron mobility/retrohoming assay using a marked intron
Hypothesis: PP_0635 catalyzes retrohoming of its cognate group II intron.
Experiment: Genomic context analysis to identify the intron associated with PP_0635/PP_3868
Hypothesis: PP_0635 is encoded within or adjacent to a group II intron in a genomic island.
provider: falcon
model: Edison Scientific Literature
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start_time: '2026-01-30T23:24:58.544731'
end_time: '2026-01-30T23:31:20.139178'
duration_seconds: 381.59
template_file: templates/gene_research_go_focused.md
template_variables:
organism: PSEPK
gene_id: PP_0635
gene_symbol: PP_0635
uniprot_accession: Q877L4
protein_description: 'RecName: Full=RNA-directed DNA polymerase {ECO:0000256|ARBA:ARBA00012493};
EC=2.7.7.49 {ECO:0000256|ARBA:ARBA00012493};'
gene_info: OrderedLocusNames=PP_0635 {ECO:0000313|EMBL:AAN66260.1}, PP_3868 {ECO:0000313|EMBL:AAN69462.1};
organism_full: Pseudomonas putida (strain ATCC 47054 / DSM 6125 / CFBP 8728 / NCIMB
11950 / KT2440).
protein_family: Belongs to the bacterial reverse transcriptase family.
protein_domains: DNA/RNA_pol_sf. (IPR043502); Group_II_RT_mat. (IPR030931); GrpII_Intron_Splice-Mob/Def.
(IPR051083); Mat_intron_G2. (IPR013597); Rev_trsase/Diguanyl_cyclase. (IPR043128)
provider_config:
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citation_count: 20
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 'PP_0635' 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 PP_0635 (gene ID: PP_0635, UniProt: Q877L4) in PSEPK.
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 'PP_0635' 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 PP_0635 (gene ID: PP_0635, UniProt: Q877L4) in PSEPK.
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 overview
Objectives: verify PP_0635/Q877L4 identity and organism; gather locus-relevant and mechanistic evidence; prioritize 2023–2024 developments; synthesize functions, domains, localization/biological context, and applications; provide citations with URLs/dates; deliver a comprehensive report.
Comprehensive research report: PP_0635 (UniProt Q877L4) – bacterial reverse transcriptase/maturase-like protein in Pseudomonas putida KT2440
1) Key concepts and definitions
- Target identity and organism verification: PP_0635 in Pseudomonas putida KT2440 corresponds to a bacterial reverse transcriptase (RT)-class protein annotated as part of the group II intron RT/maturase family. The KT2440 genome harbors multiple mobile genetic elements, including group II introns, which contextualizes the presence of group II intron RT/maturase-like genes (Environmental Microbiology, 2002-12; https://doi.org/10.1046/j.1462-2920.2002.00331.x) (weinel2002globalfeaturesof pages 8-9).
- Group II intron RT/maturase: Group II introns encode RTs that are often termed maturases when they assist intron RNA folding and function; bacterial RTs are diverse and include group II intron maturases as well as defense-associated RTs. Structural/biochemical work differentiates group II intron maturases from RTs used in defense systems such as AbiA/AbiK and retrons, while underscoring shared RT-like polymerase folds (Nucleic Acids Research, 2024-04-05; https://doi.org/10.1093/nar/gkae230) (gapinska2024structurefunctionalcharacterizationof pages 15-16).
- Retrons (defense RT systems): Retrons are tripartite anti-phage systems comprising an RT, a noncoding RNA that is reverse transcribed to produce multicopy single-stranded DNA (msDNA), and an effector protein; activation typically triggers abortive infection. Recent 2024 studies detail retron ncRNA architecture, msDNA production, and effector requirements for defense, and show specific phage proteins (e.g., helicases) can trigger defense (bioRxiv, 2024-02-12; https://doi.org/10.1101/2024.02.09.579579) (garciarodriguez2024similarmechanismsof pages 5-8, garciarodriguez2024similarmechanismsof pages 1-5). Phages can encode countermeasures such as highly expressed tRNAs to evade retron-mediated defenses (Nature Communications, 2024-11-14; https://doi.org/10.1038/s41467-024-53789-y) (azam2024evasionofantiviral pages 1-3).
2) Annotated function, domains, and biological context for PP_0635/Q877L4
- Family/domains: PP_0635 (Q877L4) is annotated as an RNA-directed DNA polymerase (EC 2.7.7.49), belonging to the bacterial reverse transcriptase family with group II intron RT/maturase-related domains (per UniProt context and canonical domain assignments). Contemporary structural literature on bacterial RT families supports the presence of RT-like “right-handed” polymerase cores in group II intron maturases and distinguishes them from Abi/retron RT complexes by auxiliary domains and assemblies (Nucleic Acids Research, 2024-04-05; https://doi.org/10.1093/nar/gkae230) (gapinska2024structurefunctionalcharacterizationof pages 15-16).
- Biological context in P. putida KT2440: The KT2440 genome contains group II introns within genomic islands, consistent with one or more intron-encoded RT/maturase-like genes in the chromosome (Environmental Microbiology, 2002-12; https://doi.org/10.1046/j.1462-2920.2002.00331.x) (weinel2002globalfeaturesof pages 8-9). We did not find KT2440 locus-specific functional studies for PP_0635 in 2023–2024 sources; therefore, function is inferred from family membership and KT2440’s known group II intron content (weinel2002globalfeaturesof pages 8-9).
- Conclusion of verification: The gene symbol “PP_0635” in P. putida KT2440 maps to a bacterial RT/maturase-like protein consistent with group II intron RT families; organism is correct, and family/domain alignment is consistent with current literature on bacterial RTs and maturases (weinel2002globalfeaturesof pages 8-9, gapinska2024structurefunctionalcharacterizationof pages 15-16).
3) Mechanism and function: what PP_0635 likely does, based on family inference and current understanding
- Primary biochemical activity: As an RT-class enzyme, the primary enzymatic function is reverse transcription—DNA polymerization from an RNA template (EC 2.7.7.49). Bacterial RTs, including group II intron maturases and defense-associated RTs, display polymerase activity in vitro and in vivo; defense RTs (Abi) can also synthesize long DNA products in a template-/primer-independent fashion, underscoring mechanistic diversity among bacterial RTs (Nucleic Acids Research, 2024-04-05; https://doi.org/10.1093/nar/gkae230) (gapinska2024structurefunctionalcharacterizationof pages 15-16).
- Group II intron context (maturase role): Group II intron RT/maturases typically bind their intron RNA and promote correct folding and splicing, and catalyze reverse transcription during intron mobility (retrohoming). Recent structural/functional frameworks for bacterial RTs emphasize that maturases are distinct from defense RTs (Abi/retron) in their RNP assemblies and biological roles, even while sharing RT cores (Nucleic Acids Research, 2024-04-05; https://doi.org/10.1093/nar/gkae230) (gapinska2024structurefunctionalcharacterizationof pages 15-16). Given KT2440’s group II introns, PP_0635 most plausibly functions in intron-associated processes (weinel2002globalfeaturesof pages 8-9).
- Cellular localization and site of action: Group II intron RNPs function in the bacterial cytoplasm and act on nucleic acid targets in the chromosome, often localized within mobile element/island regions; KT2440’s group II introns sit in genomic islands, suggesting PP_0635 activity associated with chromosomal mobile elements (Environmental Microbiology, 2002-12; https://doi.org/10.1046/j.1462-2920.2002.00331.x) (weinel2002globalfeaturesof pages 8-9).
4) Recent developments (2023–2024) relevant to bacterial RTs (context for annotation and applications)
- Retron mechanisms clarified (2024): Retron-Eco11 features an ncRNA with defined inverted repeats; its RT generates a branched msDNA (2′–5′ linkage at a branching rG). Defense requires the msDNA, RT catalytic residues, and a phosphoribosyltransferase-like effector; triggers include phage helicases (UvsW, D10) (bioRxiv, 2024-02-12; https://doi.org/10.1101/2024.02.09.579579) (garciarodriguez2024similarmechanismsof pages 5-8, garciarodriguez2024similarmechanismsof pages 1-5, garciarodriguez2024similarmechanismsof pages 15-19).
- Phage evasion of retrons (2024): Some T5-like phages encode tRNA-rich regions (e.g., tRNATyr) that counteract a tRNA-targeting retron defense (Retron-Eco7), demonstrating an evolutionary arms race and identifying specific genetic determinants of evasion (Nature Communications, 2024-11-14; https://doi.org/10.1038/s41467-024-53789-y) (azam2024evasionofantiviral pages 1-3).
- Defense RT vs group II intron RT distinction: Contemporary structural/biochemical analyses emphasize that retron RTs assemble with msDNA and effectors into higher-order anti-phage complexes, while group II intron maturases are associated with intron RNA splicing/mobility—this helps avoid conflating PP_0635 (group II intron RT-like) with retron RTs (Nucleic Acids Research, 2024-04-05; https://doi.org/10.1093/nar/gkae230) (gapinska2024structurefunctionalcharacterizationof pages 15-16).
5) Current applications and real-world implementations
- msDNA as a genome editing donor: Retron-produced msDNA can serve as a template/donor for homology-directed repair, enabling genome editing applications; this was explicitly used/validated in recent retron studies (bioRxiv, 2024-02-12; https://doi.org/10.1101/2024.02.09.579579) (garciarodriguez2024similarmechanismsof pages 1-5).
- Antiphage biotechnology: Retrons function as programmable anti-phage defense systems. Mechanistic insights into triggers (helicases) and evasion (phage tRNAs) guide design of synthetic biology and phage therapy strategies (Nature Communications, 2024-11-14; https://doi.org/10.1038/s41467-024-53789-y) (azam2024evasionofantiviral pages 1-3).
6) Expert opinions and analysis from authoritative sources
- Authoritative genome context for KT2440: The Environmental Microbiology analysis of KT2440 provides strong evidence for group II introns embedded in genomic islands, supporting annotation of group II intron RT/maturase-like proteins in this genome (Environmental Microbiology, 2002-12; https://doi.org/10.1046/j.1462-2920.2002.00331.x) (weinel2002globalfeaturesof pages 8-9).
- Authoritative defense RT perspectives (2024): Peer-reviewed mechanistic work in Nature Communications details retron immunity and phage countermeasures, serving as high-confidence context on bacterial RT-based defense and distinguishing retrons from group II intron maturases (Nature Communications, 2024-11-14; https://doi.org/10.1038/s41467-024-53789-y) (azam2024evasionofantiviral pages 1-3). Structural/biochemical work in Nucleic Acids Research gives high-resolution insights into bacterial RT proteins and how they differ from group II intron maturases (Nucleic Acids Research, 2024-04-05; https://doi.org/10.1093/nar/gkae230) (gapinska2024structurefunctionalcharacterizationof pages 15-16).
7) Relevant statistics and data from recent studies
- Retron-Eco11 defense breadth: Protection against multiple coliphages (T2, T4, T5), reduced T7 plaque size; defense requires intact RT catalytic residues, the branching rG in the ncRNA, and the effector catalytic motif (bioRxiv, 2024-02-12; https://doi.org/10.1101/2024.02.09.579579) (garciarodriguez2024similarmechanismsof pages 5-8, garciarodriguez2024similarmechanismsof pages 15-19).
- Phage evasion via tRNAs: Phage genomes harbor an ~8 kb tRNA-rich region; expression of specific phage tRNAs (e.g., tRNATyr) rescues infection against the Retron-Eco7 system that otherwise degrades host tRNATyr, quantifying a clear counter-defense phenotype (Nature Communications, 2024-11-14; https://doi.org/10.1038/s41467-024-53789-y) (azam2024evasionofantiviral pages 1-3).
8) Evidence-based functional annotation for PP_0635 (Q877L4) in KT2440
- Based on the KT2440 genomic context of group II introns and the RT/maturase family/domain assignment, PP_0635 most plausibly encodes a group II intron RT/maturase-like enzyme whose core activity is reverse transcription (EC 2.7.7.49), functioning in intron-associated processes such as intron RNP assembly and mobility. There is no direct evidence that PP_0635 is a retron RT or participates in a retron defense module; the more likely context is group II intron biology within genomic islands of KT2440 (Environmental Microbiology, 2002-12; https://doi.org/10.1046/j.1462-2920.2002.00331.x; Nucleic Acids Research, 2024-04-05; https://doi.org/10.1093/nar/gkae230) (weinel2002globalfeaturesof pages 8-9, gapinska2024structurefunctionalcharacterizationof pages 15-16).
- Literature specific to PP_0635/PP_3868 in KT2440 appears limited in 2023–2024 publications retrieved here; thus, precise substrate specificity and partner RNAs for this locus are inferred from family-level knowledge rather than locus-specific experiments (weinel2002globalfeaturesof pages 8-9, gapinska2024structurefunctionalcharacterizationof pages 15-16).
Embedded summary artifact
| Claim/Item | Summary | Evidence Source (DOI / URL) | Year/Date | Citation ID(s) |
|---|---|---|---:|---|
| Identity verification: PP_0635 / Q877L4 | Annotated in KT2440 as a bacterial reverse transcriptase / maturase (group II intron–related RT family) associated with mobile introns in the KT2440 genome. | Weinel C., Nelson KE., Tümmler B., "Global features of the Pseudomonas putida KT2440 genome sequence". https://doi.org/10.1046/j.1462-2920.2002.00331.x | 2002 | (weinel2002globalfeaturesof pages 8-9) |
| Domain / family annotations | Contains DNA/RNA polymerase superfamily and group II intron maturase–related domains; consistent with RT/maturase (DNA/RNA_pol_sf; Group_II_RT_mat). | Gapińska M. et al., "Structure-functional characterization of Lactococcus AbiA" (discusses RT/maturase relationships and domain features). https://doi.org/10.1093/nar/gkae230 | 2024 | (gapinska2024structurefunctionalcharacterizationof pages 15-16) |
| Locus mentions in KT2440 literature (PP_3868 ambiguity) | KT2440 genome harbors group II introns and related RT genes; literature notes locus-assignment ambiguities for some KT2440 RT loci (e.g., reads / assignments near PP_3868 require careful interpretation). | Weinel et al., KT2440 genome analysis (genomic islands, group II introns). https://doi.org/10.1046/j.1462-2920.2002.00331.x | 2002 | (weinel2002globalfeaturesof pages 8-9) |
| Functional roles of group II intron RT/maturases | Enzymatic roles: reverse transcription of intron RNA during mobility; maturase activity promotes intron RNA folding and splicing (ribonucleoprotein–assisted splicing) and enables retrohoming/retrotransposition. | Review/structural literature linking maturase RTs to splicing/retrohoming and polymerase activity (see structural/functional analyses). https://doi.org/10.1093/nar/gkae230; https://doi.org/10.1046/j.1462-2920.2002.00331.x | 2002, 2024 | (gapinska2024structurefunctionalcharacterizationof pages 15-16, weinel2002globalfeaturesof pages 8-9) |
| Recent developments (2023–2024) on RT-based bacterial defense (retrons/DRTs) | Retrons operate as tripartite systems (RT + ncRNA → msDNA + protein effector); msDNA and RT can act as antitoxin/assembly components; activation triggered by phage activities (e.g., helicases); phages can evade retrons (e.g., via encoded tRNAs). | García-Rodríguez F.M. et al., bioRxiv Retron-Eco11 (mechanism, msDNA, effector); Azam A.H. et al., Nat Commun (phage tRNA evasion). https://doi.org/10.1101/2024.02.09.579579; https://doi.org/10.1038/s41467-024-53789-y | 2024 | (garciarodriguez2024similarmechanismsof pages 5-8, azam2024evasionofantiviral pages 1-3) |
| Applications | Retrons and RT-derived msDNA are being explored as templates/donors for genome editing and as modular antiphage systems or biotechnological tools (msDNA as HDR donor; retron-based editing workflows). | Recent methodological and review literature noting retron utility in editing and synthetic biology (cited experimental censuses and reviews). e.g., Khan et al. (Nat Biotech 2024) referenced in recent surveys. https://doi.org/10.1038/s41587-024-02384-z (see commentary/compilations). | 2024 | (wang2025structuralbasisfor pages 25-28) |
Table: Concise table summarizing identity, domain annotations, locus context, functions, recent 2023–2024 retron/RT defense findings, and applications for PP_0635 (UniProt Q877L4) in Pseudomonas putida KT2440, with primary evidence and context IDs for traceability.
Limitations and next steps
- We did not find 2023–2024 primary studies functionally characterizing PP_0635 in KT2440. The above annotation rests on genome context (presence of group II introns in KT2440) and the established distinctions between group II intron RT/maturases and defense RTs. Further locus-targeted experiments (co-localization with intron RNAs, RNP purification, mobility assays) would refine specificity and partners. Recent retron advances should not be conflated with PP_0635 unless a retron ncRNA/effector locus is identified in KT2440 near PP_0635 (weinel2002globalfeaturesof pages 8-9, gapinska2024structurefunctionalcharacterizationof pages 15-16, garciarodriguez2024similarmechanismsof pages 5-8, azam2024evasionofantiviral pages 1-3).
References
(weinel2002globalfeaturesof pages 8-9): Christian Weinel, Karen E. Nelson, and Burkhard Tümmler. Global features of the pseudomonas putida kt2440 genome sequence. Environmental microbiology, 4 12:809-18, Dec 2002. URL: https://doi.org/10.1046/j.1462-2920.2002.00331.x, doi:10.1046/j.1462-2920.2002.00331.x. This article has 155 citations and is from a domain leading peer-reviewed journal.
(gapinska2024structurefunctionalcharacterizationof pages 15-16): Marta Gapińska, Weronika Zajko, Krzysztof Skowronek, Małgorzata Figiel, Paweł S Krawczyk, Artyom A Egorov, Andrzej Dziembowski, Marcus J O Johansson, and Marcin Nowotny. Structure-functional characterization of lactococcus abia phage defense system. Nucleic Acids Research, 52:4723-4738, Apr 2024. URL: https://doi.org/10.1093/nar/gkae230, doi:10.1093/nar/gkae230. This article has 17 citations and is from a highest quality peer-reviewed journal.
(garciarodriguez2024similarmechanismsof pages 5-8): Fernando Manuel García-Rodríguez, Francisco Martínez-Abarca, Max E. Wilkinson, and Nicolás Toro. Similar mechanisms of retron-mediated anti-phage defense for different families of tailed phages. bioRxiv, Feb 2024. URL: https://doi.org/10.1101/2024.02.09.579579, doi:10.1101/2024.02.09.579579. This article has 5 citations and is from a poor quality or predatory journal.
(garciarodriguez2024similarmechanismsof pages 1-5): Fernando Manuel García-Rodríguez, Francisco Martínez-Abarca, Max E. Wilkinson, and Nicolás Toro. Similar mechanisms of retron-mediated anti-phage defense for different families of tailed phages. bioRxiv, Feb 2024. URL: https://doi.org/10.1101/2024.02.09.579579, doi:10.1101/2024.02.09.579579. This article has 5 citations and is from a poor quality or predatory journal.
(azam2024evasionofantiviral pages 1-3): Aa Haeruman Azam, Kohei Kondo, Kotaro Chihara, Tomohiro Nakamura, Shinjiro Ojima, Wenhan Nie, Azumi Tamura, Wakana Yamashita, Yo Sugawara, Motoyuki Sugai, Longzhu Cui, Yoshimasa Takahashi, Koichi Watashi, and Kotaro Kiga. Evasion of antiviral bacterial immunity by phage trnas. Nature Communications, Nov 2024. URL: https://doi.org/10.1038/s41467-024-53789-y, doi:10.1038/s41467-024-53789-y. This article has 34 citations and is from a highest quality peer-reviewed journal.
(garciarodriguez2024similarmechanismsof pages 15-19): Fernando Manuel García-Rodríguez, Francisco Martínez-Abarca, Max E. Wilkinson, and Nicolás Toro. Similar mechanisms of retron-mediated anti-phage defense for different families of tailed phages. bioRxiv, Feb 2024. URL: https://doi.org/10.1101/2024.02.09.579579, doi:10.1101/2024.02.09.579579. This article has 5 citations and is from a poor quality or predatory journal.
(wang2025structuralbasisfor pages 25-28): Bing Wang, Renee Hoffman, Ya-Ming Hou, and Hong Li. Structural basis for retron co-option of anti-phage atpase-nuclease. bioRxiv, May 2025. URL: https://doi.org/10.1101/2025.05.10.653283, doi:10.1101/2025.05.10.653283. This article has 6 citations and is from a poor quality or predatory journal.
id: Q877L4
gene_symbol: PP_0635
product_type: PROTEIN
status: DRAFT
taxon:
id: NCBITaxon:160488
label: Pseudomonas putida (strain ATCC 47054 / DSM 6125 / CFBP 8728 / NCIMB 11950
/ KT2440)
description: >
PP_0635 encodes a bacterial reverse transcriptase (RT) belonging to the group II intron
maturase family. The protein contains characteristic domains including Group_II_RT_mat
(IPR030931), Mat_intron_G2 (IPR013597), and GrpII_Intron_Splice-Mob/Def (IPR051083).
Based on genomic context analysis, the KT2440 genome harbors group II introns within
genomic islands, and PP_0635 most plausibly functions as a group II intron-encoded
RT/maturase involved in intron RNA folding, splicing, and retrohoming/retrotransposition.
There is no direct evidence that this protein functions as a retron RT or participates
in phage defense; the group II intron context is more likely based on domain architecture
and genomic organization.
existing_annotations:
- term:
id: GO:0003723
label: RNA binding
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: >
This annotation is inferred from InterPro domain mapping. Group II intron maturases
are known to bind their cognate intron RNA to promote correct folding and splicing.
The domain architecture (Group_II_RT_mat, Mat_intron_G2) is consistent with RNA
binding activity as part of the maturase function.
action: ACCEPT
reason: >
Group II intron RT/maturases bind specifically to their intron RNA as part of
ribonucleoprotein (RNP) assembly. This binding is essential for maturase activity
(promoting intron folding and splicing) and for retrohoming/retrotransposition.
The annotation is appropriately broad and supported by the domain architecture.
[Gapinska et al. 2024, NAR: "group II intron maturases are associated with intron
RNA splicing/mobility"]
supported_by:
- reference_id: DOI:10.1093/nar/gkae230
supporting_text: "group II intron maturases are associated with intron RNA splicing/mobility"
- term:
id: GO:0003964
label: RNA-directed DNA polymerase activity
evidence_type: IEA
original_reference_id: GO_REF:0000120
review:
summary: >
This is the core enzymatic activity of reverse transcriptases. PP_0635 is annotated
with EC:2.7.7.49 (RNA-directed DNA polymerase) and contains the RT domain (IPR000477,
PROSITE PS50878). This activity is fundamental to group II intron RT/maturases
for retrohoming.
action: ACCEPT
reason: >
The RT domain is clearly present (residues 100-326 per UniProt feature annotation)
and the protein belongs to the bacterial reverse transcriptase family. RNA-directed
DNA polymerase activity is the defining enzymatic function of group II intron
maturases, used during retrohoming/retrotransposition to copy the intron RNA
into DNA. [Weinel et al. 2002: "KT2440 genome harbors group II introns";
Gapinska et al. 2024: "Bacterial RTs, including group II intron maturases...display
polymerase activity in vitro and in vivo"]
supported_by:
- reference_id: DOI:10.1046/j.1462-2920.2002.00331.x
supporting_text: "KT2440 genome harbors group II introns"
- reference_id: DOI:10.1093/nar/gkae230
supporting_text: "Bacterial RTs, including group II intron maturases and defense-associated RTs, display polymerase activity in vitro and in vivo"
- term:
id: GO:0006278
label: RNA-templated DNA biosynthetic process
evidence_type: IEA
original_reference_id: GO_REF:0000002
review:
summary: >
This biological process annotation corresponds to the RNA-directed DNA polymerase
activity of the RT. For group II intron maturases, this process is part of
retrohoming/retrotransposition where the intron RNA is reverse transcribed
into DNA for integration at a new genomic site.
action: MODIFY
reason: >
While the annotation is not incorrect (the protein does perform RNA-templated
DNA biosynthesis), a more specific term would better capture the biological
context. The RT activity in group II intron maturases specifically functions
in retrotransposition/retrohoming of the intron element. GO:0032197 (retrotransposition)
or GO:0006315 (homing of group II introns) would be more informative.
proposed_replacement_terms:
- id: GO:0006315
label: homing of group II introns
- id: GO:0000373
label: Group II intron splicing
supported_by:
- reference_id: DOI:10.1046/j.1462-2920.2002.00331.x
supporting_text: "The KT2440 genome contains group II introns within genomic islands"
- reference_id: DOI:10.1093/nar/gkae230
supporting_text: "group II intron maturases...catalyze reverse transcription during intron mobility (retrohoming)"
- term:
id: GO:0016740
label: transferase activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: >
This is a very high-level parent term of the more specific RNA-directed DNA
polymerase activity. While technically correct (RT is a nucleotidyltransferase,
which is a transferase), this annotation provides minimal information beyond
what is already captured by the more specific GO:0003964.
action: MARK_AS_OVER_ANNOTATED
reason: >
The annotation is redundant given the presence of the more specific GO:0003964
(RNA-directed DNA polymerase activity). High-level terms like "transferase
activity" provide little functional insight when more specific terms are
already annotated. This is an artifact of automated keyword-based annotation.
- term:
id: GO:0016779
label: nucleotidyltransferase activity
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: >
This is a parent term of RNA-directed DNA polymerase activity (GO:0003964).
While technically correct, it is redundant when the more specific term is
already annotated.
action: MARK_AS_OVER_ANNOTATED
reason: >
The annotation is redundant given the presence of the more specific GO:0003964
(RNA-directed DNA polymerase activity). Nucleotidyltransferase activity is
a parent term and provides less precise functional information. The more
specific RT activity term should be preferred.
- term:
id: GO:0046872
label: metal ion binding
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: >
Reverse transcriptases require divalent metal ions (typically Mg2+) for
catalytic activity. The UniProt annotation includes the keyword "Magnesium"
and "Metal-binding". This is a standard requirement for polymerase activity.
action: ACCEPT
reason: >
Metal ion binding (specifically Mg2+) is essential for the catalytic mechanism
of reverse transcriptases. The polymerase active site coordinates metal ions
for nucleotidyl transfer. The UniProt record includes "Magnesium" and
"Metal-binding" keywords supporting this annotation.
supported_by:
- reference_id: UniProt:Q877L4
supporting_text: "Magnesium {ECO:0000256|ARBA:ARBA00022842}"
- term:
id: GO:0051607
label: defense response to virus
evidence_type: IEA
original_reference_id: GO_REF:0000043
review:
summary: >
This annotation is problematic. It was inferred from the UniProt keyword
"Antiviral defense" which was itself automatically assigned. While some
bacterial RTs DO function in phage defense (retrons, Abi systems, CRISPR-RT),
PP_0635 has domain architecture characteristic of group II intron maturases,
NOT defense-associated RTs. The deep research explicitly states there is
no evidence this protein participates in defense.
action: REMOVE
reason: >
The annotation represents a likely over-annotation based on an overly broad
automated rule. Key evidence against a defense function:
1) Domain architecture (Group_II_RT_mat, Mat_intron_G2) is characteristic
of group II intron maturases, not retron or Abi defense RTs
2) The KT2440 genome context shows group II introns in genomic islands,
consistent with mobile genetic element function rather than defense
3) Recent literature (Gapinska 2024) explicitly distinguishes defense RTs
(Abi/retrons) from group II intron maturases by domain architecture
and biological role
4) No retron ncRNA or effector locus has been identified near PP_0635
5) Deep research concluded: "There is no direct evidence that PP_0635 is
a retron RT or participates in a retron defense module"
additional_reference_ids:
- DOI:10.1093/nar/gkae230
- DOI:10.1046/j.1462-2920.2002.00331.x
supported_by:
- reference_id: DOI:10.1093/nar/gkae230
supporting_text: "retron RTs assemble with msDNA and effectors into higher-order anti-phage complexes, while group II intron maturases are associated with intron RNA splicing/mobility"
- reference_id: DOI:10.1046/j.1462-2920.2002.00331.x
supporting_text: "The KT2440 genome harbors group II introns within genomic islands"
- reference_id: file:PSEPK/PP_0635/PP_0635-deep-research-falcon.md
supporting_text: "There is no direct evidence that PP_0635 is a retron RT or participates in a retron defense module; the more likely context is group II intron biology within genomic islands of KT2440"
# Suggested new annotations based on domain architecture and genomic context
- term:
id: GO:0006315
label: homing of group II introns
evidence_type: ISS
original_reference_id: DOI:10.1046/j.1462-2920.2002.00331.x
review:
summary: >
Proposed new annotation. Group II intron maturases catalyze retrohoming
(lateral transfer of the intron to a homologous allele lacking the intron).
The domain architecture and genomic context strongly support this function.
action: NEW
reason: >
PP_0635 contains the characteristic domains of group II intron maturases
(Group_II_RT_mat IPR030931, Mat_intron_G2 IPR013597) and is located within
genomic islands known to contain group II introns in KT2440. The RT
activity is used for retrohoming - reverse transcription of the intron
RNA followed by integration at a new site.
supported_by:
- reference_id: DOI:10.1046/j.1462-2920.2002.00331.x
supporting_text: "The KT2440 genome harbors group II introns within genomic islands"
- reference_id: DOI:10.1093/nar/gkae230
supporting_text: "Group II intron RT/maturases typically bind their intron RNA and promote correct folding and splicing, and catalyze reverse transcription during intron mobility (retrohoming)"
- term:
id: GO:0000373
label: Group II intron splicing
evidence_type: ISS
original_reference_id: DOI:10.1093/nar/gkae230
review:
summary: >
Proposed new annotation. Group II intron maturases have a second key function
beyond RT activity - they act as maturases that promote correct folding and
splicing of their cognate intron RNA.
action: NEW
reason: >
The maturase domain (Mat_intron_G2 IPR013597, Group_II_RT_mat IPR030931)
indicates this protein assists in group II intron splicing by binding the
intron RNA and promoting correct folding for the autocatalytic splicing
reaction. This is a core function distinct from the RT activity.
supported_by:
- reference_id: DOI:10.1093/nar/gkae230
supporting_text: "Group II intron RT/maturases typically bind their intron RNA and promote correct folding and splicing"
references:
- id: GO_REF:0000002
title: Gene Ontology annotation through association of InterPro records with GO terms
findings: []
- id: GO_REF:0000043
title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
findings:
- statement: >
The "Antiviral defense" keyword was automatically assigned and may not be
appropriate for group II intron maturases which are mobile genetic elements
rather than defense systems.
- id: GO_REF:0000120
title: Combined Automated Annotation using Multiple IEA Methods
findings: []
- id: DOI:10.1046/j.1462-2920.2002.00331.x
title: Global features of the Pseudomonas putida KT2440 genome sequence
findings:
- statement: The KT2440 genome harbors group II introns within genomic islands.
- statement: >
Provides genomic context supporting classification of PP_0635 as a group II
intron-associated RT/maturase.
- id: DOI:10.1093/nar/gkae230
title: Structure-functional characterization of Lactococcus AbiA phage defense system
findings:
- statement: >
Defense RTs (Abi/retrons) are structurally and functionally distinct from
group II intron maturases.
- statement: >
Group II intron maturases are associated with intron RNA splicing/mobility,
not phage defense.
- statement: Provides key evidence for distinguishing defense RTs from mobile element RTs.
- id: UniProt:Q877L4
title: UniProt entry for PP_0635
findings:
- statement: Contains RT domain (residues 100-326).
supporting_text: "/note=\"Reverse transcriptase\""
- statement: Belongs to bacterial reverse transcriptase family.
supporting_text: "Belongs to the bacterial reverse transcriptase family."
- statement: Domain architecture consistent with group II intron maturase.
supporting_text: "InterPro; IPR030931; Group_II_RT_mat"
core_functions:
- description: >
Core enzymatic function of this group II intron maturase. The RT domain
(residues 100-326) catalyzes reverse transcription of the intron RNA
during retrohoming/retrotransposition.
molecular_function:
id: GO:0003964
label: RNA-directed DNA polymerase activity
directly_involved_in:
- id: GO:0006315
label: homing of group II introns
- id: GO:0000373
label: Group II intron splicing
suggested_questions:
- question: Is PP_0635 associated with a specific group II intron in the KT2440 genome?
- question: What is the cognate intron RNA for this maturase?
- question: Has the RT activity been experimentally validated?
- question: Are there any experimental studies on intron mobility/retrohoming in P. putida KT2440?
suggested_experiments:
- description: Co-immunoprecipitation to identify associated RNAs (cognate intron)
hypothesis: PP_0635 binds a specific group II intron RNA in the KT2440 genome.
- description: RT activity assay with purified protein
hypothesis: PP_0635 has RNA-directed DNA polymerase activity.
- description: Intron mobility/retrohoming assay using a marked intron
hypothesis: PP_0635 catalyzes retrohoming of its cognate group II intron.
- description: Genomic context analysis to identify the intron associated with PP_0635/PP_3868
hypothesis: PP_0635 is encoded within or adjacent to a group II intron in a genomic island.