D15

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0003677 DNA binding	IEA GO_REF:0000120	MODIFY	Summary: DNA binding is correct but is the least informative statement available for this protein: its binding is structure-selective, detectable on 5' overhangs, flaps and pseudo-Y junctions and undetectable on blunt duplexes or free single strands. Reason: The UniRule/keyword mapping lands on the root DNA-binding term, while the primary literature establishes which DNA structures are bound. EMSA across a panel of defined substrates shows binding to 5'-overhanging, flap and pseudo-Y duplexes and no detectable binding to blunt-ended duplexes or single-stranded oligonucleotides (PMID:9380501), and the crystal structures resolve the flap/overhang substrate in pre-threading and fully threaded complexes (PMID:27273516). GO:0000403 Y-form DNA binding and GO:0070338 5'-flap-structured DNA binding are is_a descendants of GO:0003677 that state exactly this, so the row is refined rather than removed; the metal-free EMSA conditions of PMID:9380501 separate binding from catalysis. Proposed replacements: Y-form DNA binding 5'-flap-structured DNA binding Supporting Evidence: PMID:9380501 However, duplexes with 5'-overhangs, flaps and pseudo-Y structures showed decreased mobility with added T5 exonuclease. PMID:9380501 Binding of T5 exonuclease to either blunt-ended duplexes or single-stranded oligonucleotides could not be detected by EMSA. file:BPT5/D15/D15-uniprot.txt K->A: No exonuclease activity, retains full endonuclease activity on a flap structure. Binds DNA pseudo-Y substrates with a dissociation constant of 200 nM.
GO:0003824 catalytic activity	IEA GO_REF:0000002	TOO GENERAL	Summary: Root-level catalytic activity from an InterPro2GO mapping; true but entailed by the specific nuclease activities accepted in this review. Reason: The protein is a characterised hydrolase with measured steady-state parameters (PMID:9889266, PMID:10364212), and GO:0051908 and GO:0017108 are accepted here; both are descendants of GO:0003824, which therefore adds nothing. The claim is not in doubt, only uninformative. Supporting Evidence: PMID:9889266 The steady-state catalytic parameters of the enzyme are reported and it is concluded that T5 5'-->3' exonuclease accelerates the cleavage of a specific phosphodiester bond by a factor of at least 10(15).
GO:0004518 nuclease activity	IEA GO_REF:0000043	TOO GENERAL	Summary: Keyword-derived nuclease activity; correct, and entailed by the specific exonuclease and flap-endonuclease terms accepted in this review. Reason: KW-0540 Nuclease maps to the root nuclease term. Both of this protein's activities are documented at far greater specificity (PMID:17559871), and GO:0051908 and GO:0017108 are accepted, so GO:0004518 is redundant rather than wrong. Supporting Evidence: PMID:17559871 Flap endonucleases (FENs) catalyse the exonucleolytic hydrolysis of blunt-ended duplex DNA substrates and the endonucleolytic cleavage of 5'-bifurcated nucleic acids at the junction formed between single and double-stranded DNA.
GO:0004519 endonuclease activity	IEA GO_REF:0000043	TOO GENERAL	Summary: Keyword-derived endonuclease activity, entailed by the accepted GO:0017108 5'-flap endonuclease activity. Reason: The endonucleolytic reaction is strictly structure-specific, requiring a free single-stranded 5' end and cleaving at the single/double-stranded junction (PMID:17559871, PMID:9874768). GO:0017108 is an is_a descendant of GO:0004519 and is accepted here, so the generic term is uninformative; it also invites the misreading that the enzyme is a general-purpose endonuclease, which PMID:2211703 argues against. Supporting Evidence: PMID:9874768 Biochemical analysis demonstrated that K83 is absolutely required for exonucleolytic activity on single-stranded DNA but is not required for endonucleolytic cleavage of flap structures.
GO:0004527 exonuclease activity	IEA GO_REF:0000043	TOO GENERAL	Summary: Keyword-derived exonuclease activity, entailed by the accepted GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity. Reason: The direction (5'-3'), the substrate (DNA) and the product (nucleoside 5'-phosphates, EC 3.1.11.3) are all established (PMID:2211703, PMID:17559871), and the corresponding specific terms are accepted in this review, of which GO:0004527 is an ancestor. Supporting Evidence: PMID:2211703 The purified enzyme is active on both native and heat-denatured DNA and shows no endonuclease activity on either double-stranded closed-circular or nicked DNA.
GO:0004529 DNA exonuclease activity	IDA PMID:10364212 Variation in the steady state kinetic parameters of wild typ...	MODIFY	Summary: Steady-state kinetic characterisation of the purified enzyme and of the K83A mutant across pH; the activity assayed is DNA exonucleolysis, but the term omits the direction, which this enzyme family is defined by. Reason: The claim is right; the granularity is not. GO:0004529 covers cleavage from either terminus, whereas the enzyme is strictly 5'-3' (PMID:10364212 titles the protein T5 5'-3'-exonuclease and PMID:2211703 equates its mode of action with the 5'-3' exonuclease of E. coli DNA polymerase I). GO:0035312 is an is_a descendant that the gene already carries, and GO:0051908 adds the duplex substrate; both are supported by this body of work, so both are proposed. Proposed replacements: 5'-3' DNA exonuclease activity double-stranded DNA 5'-3' DNA exonuclease activity Supporting Evidence: PMID:10364212 T5 5'-3'-exonuclease is a member of a family of homologous 5'-nucleases essential for DNA replication and repair. PMID:2211703 The mode of action of this enzyme is similar to, although not identical to that of the 5'-3' exonuclease activity of E. coli DNA polymerase I.
GO:0004529 DNA exonuclease activity	IDA PMID:17559871 Comparison of the catalytic parameters and reaction specific...	MODIFY	Summary: Direct assay of T5 FEN against a panel of defined oligonucleotide substrates, including blunt duplexes degraded exonucleolytically; the term omits the 5'-3' direction. Reason: Same refinement as the other GO:0004529 rows. This paper assays the phage enzyme side by side with an archaeal FEN and reports exonucleolytic hydrolysis of blunt-ended duplex DNA, which is GO:0051908, itself a descendant of GO:0035312 and of GO:0004529. The directionality is the informative part and is well established. Proposed replacements: 5'-3' DNA exonuclease activity double-stranded DNA 5'-3' DNA exonuclease activity Supporting Evidence: PMID:17559871 Flap endonucleases (FENs) catalyse the exonucleolytic hydrolysis of blunt-ended duplex DNA substrates and the endonucleolytic cleavage of 5'-bifurcated nucleic acids at the junction formed between single and double-stranded DNA. PMID:17559871 The phage enzyme produced multiple reaction products of differing length with all the substrates tested, except when the length of duplex DNA downstream of the reaction site was truncated.
GO:0004529 DNA exonuclease activity	IDA PMID:2211703 Properties of overexpressed phage T5 D15 exonuclease. Simila...	MODIFY	Summary: The original characterisation of homogeneous overexpressed D15: active on native and heat-denatured DNA, with a mode of action matching the 5'-3' exonuclease of E. coli DNA polymerase I. Reason: Correct but under-specified, as for the other GO:0004529 rows. This paper is the source UniProt cites for EC 3.1.11.3 and for N-terminal processing of the protein, and it fixes the direction of the reaction by homology and by assay; GO:0035312 and GO:0051908 state it. Proposed replacements: 5'-3' DNA exonuclease activity double-stranded DNA 5'-3' DNA exonuclease activity Supporting Evidence: PMID:2211703 The purified enzyme is active on both native and heat-denatured DNA and shows no endonuclease activity on either double-stranded closed-circular or nicked DNA. PMID:2211703 The mode of action of this enzyme is similar to, although not identical to that of the 5'-3' exonuclease activity of E. coli DNA polymerase I.
GO:0004529 DNA exonuclease activity	IDA PMID:27273516 Direct observation of DNA threading in flap endonuclease com...	MODIFY	Summary: Gel assays in the structural paper show wild-type T5 FEN digesting a single-stranded oligonucleotide while the active-site variants D153K and D155K are inactive; the term again omits the direction. Reason: The row is sound and this is the one cited paper whose full text is available: the enzyme digests dT12 to short products and the catalytic-aspartate variants do not, which is DNA exonucleolysis by the gene D15 product. GO:0035312 and GO:0051908 capture the 5'-3' direction and the duplex substrate, and both are already carried. Proposed replacements: 5'-3' DNA exonuclease activity double-stranded DNA 5'-3' DNA exonuclease activity Supporting Evidence: PMID:27273516 neither variant T5FenD153K nor a second variant, D155K, showed activity file:BPT5/D15/D15-uniprot.txt Reaction=Exonucleolytic cleavage in the 5'- to 3'-direction to yield
GO:0004529 DNA exonuclease activity	IDA PMID:9380501 Structure-specific DNA binding by bacteriophage T5 5'-->3' e...	MODIFY	Summary: Substrate-binding study that also characterises the catalytic properties of wild-type and cysteine-substituted enzyme; the exonucleolytic activity is the starting point of the paper. Reason: Correct but under-specified. The paper's opening statement defines the protein as a 5'-3' exodeoxyribonuclease that in addition cleaves flap structures endonucleolytically, so the direction-specific descendants GO:0035312 and GO:0051908 are the right level; GO:0004529 is their ancestor. Proposed replacements: 5'-3' DNA exonuclease activity double-stranded DNA 5'-3' DNA exonuclease activity Supporting Evidence: PMID:9380501 Phage T5 exonuclease is a 5'-->3'exodeoxyribonuclease that also exhibits endonucleolytic activity on flap structures (branched duplex DNA containing a free single-stranded 5'-end).
GO:0004529 DNA exonuclease activity	IMP PMID:9889266 A single cleavage assay for T5 5'-->3' exonuclease: determin...	MODIFY	Summary: Catalytic parameters of wild-type and of the K83A, K196A and K215A mutants in a single-cleavage assay; the mutational analysis is what makes this an IMP, and the activity measured is 5'-3' DNA exonucleolysis and structure-specific cleavage. Reason: The claim holds and is strengthened by the mutant series; only the term's granularity is at issue, as for the other GO:0004529 rows. GO:0035312 and GO:0051908 state the direction and substrate. Proposed replacements: 5'-3' DNA exonuclease activity double-stranded DNA 5'-3' DNA exonuclease activity Supporting Evidence: PMID:9889266 The 5'-nucleases have both exonucleolytic and structure-specific endo-nucleolytic DNA cleavage activity and are conserved in organisms as diverse as bacteriophage and mammals. PMID:9889266 Mutation of any of these three lysine residues to alanine is detrimental to catalytic efficiency.
GO:0006260 DNA replication	IEA GO_REF:0000043	MODIFY	Summary: Keyword-derived generic DNA replication. For a phage protein the specific and correct process is replication of the viral genome, which the gene already carries. Reason: KW-0235 DNA replication maps to the cellular process term, but D15 acts on the T5 genome during phage replication, not on host chromosome replication; the viral keyword KW-1194 is also present on this entry and gives GO:0039693, which is accepted here. Replacing the generic term with GO:0039693 keeps the claim and locates it correctly. Proposed replacements: viral DNA genome replication Supporting Evidence: PMID:6248541 the proteins gpD5 (DNA-binding protein), and gpD15 (nuclease) which are both known to be essential for T5 DNA replication and for the initiation of late transcription file:BPT5/D15/D15-uniprot.txt probably plays a role in viral genome replication
GO:0008409 5'-3' exonuclease activity	IDA PMID:9874768 Mutagenesis of conserved lysine residues in bacteriophage T5...	MODIFY	Summary: Direct assay of wild-type and lysine-mutant enzyme showing 5'-3' exonucleolysis of single-stranded DNA, separable from flap endonucleolysis; the term does not say that the substrate is DNA. Reason: GO:0008409 covers nucleic acids generally. What is assayed here is DNA, both single-stranded (abolished by K83A) and duplex, so GO:0035312 5'-3' DNA exonuclease activity, an is_a descendant that this gene already carries, is the right level; GO:0051908 adds the duplex case. Note that the single-stranded substrate range is why GO:0035312 is not itself redundant against GO:0051908. Proposed replacements: 5'-3' DNA exonuclease activity double-stranded DNA 5'-3' DNA exonuclease activity Supporting Evidence: PMID:9874768 Biochemical analysis demonstrated that K83 is absolutely required for exonucleolytic activity on single-stranded DNA but is not required for endonucleolytic cleavage of flap structures. PMID:9874768 Efficient cellular DNA replication requires the activity of a 5'-3' exonuclease.
GO:0008409 5'-3' exonuclease activity	IEA GO_REF:0000120	MODIFY	Summary: UniRule/InterPro mapping of the 5'-3' exonuclease signature; correct in direction but not substrate-specific. Reason: The IPR002421 5-3_exonuclease signature and HAMAP-Rule MF_04140 identify the domain correctly, and the direction is right; the experimentally established activity is on DNA, so GO:0035312 (and GO:0051908 for the duplex substrate) is the appropriate descendant. Treated the same way as the IDA row for this term, since a review judges the claim and not the evidence code. Proposed replacements: 5'-3' DNA exonuclease activity double-stranded DNA 5'-3' DNA exonuclease activity Supporting Evidence: file:BPT5/D15/D15-uniprot.txt Pfam; PF01367; 5_3_exonuc; 1. PMID:2211703 shows a high degree of homology with the first 320 amino acid residues of Escherichia coli DNA polymerase I, the region containing the enzyme's 5'-3' exonuclease activity
GO:0016787 hydrolase activity	IEA GO_REF:0000043	TOO GENERAL	Summary: Keyword-derived root hydrolase term, entailed by the specific phosphodiesterase activities accepted in this review. Reason: The enzyme hydrolyses phosphodiester bonds with a two-metal mechanism and the reaction is written out as EC 3.1.11.3; GO:0051908 and GO:0017108, both descendants of GO:0016787, are accepted here, leaving the root term true but uninformative. Supporting Evidence: PMID:15077103 Divalent metal ions are essential cofactors in both reactions.
GO:0017108 5'-flap endonuclease activity	IDA PMID:10364212 Variation in the steady state kinetic parameters of wild typ...	ACCEPT	Summary: Kinetic characterisation of the structure-specific reaction of the purified enzyme and of the K83A variant, which retains flap cleavage while losing exonucleolysis. Reason: This is one of the gene's two core activities and the term is at exactly the right granularity: cleavage of a branched duplex bearing a free single-stranded 5' end, at the junction between single- and double-stranded DNA. The K83A separation of function (PMID:10364212, PMID:9874768) shows the endonucleolytic reaction is a distinct, intrinsic property of this protein rather than a side effect of the exonuclease. Supporting Evidence: file:BPT5/D15/D15-uniprot.txt K->A: No exonuclease activity, retains full endonuclease activity on a flap structure. file:BPT5/D15/D15-uniprot.txt The substrates require a free, single-stranded 5' end, with endonucleolytic hydrolysis occurring at the junction of double- and single-stranded DNA
GO:0017108 5'-flap endonuclease activity	IDA PMID:15077103 Roles of divalent metal ions in flap endonuclease-substrate ...	ACCEPT	Summary: Metal-site mutants (site II aspartates) lose exonuclease action but retain structure-specific flap endonuclease activity, which also establishes that one metal ion suffices for the endonucleolytic reaction. Reason: Direct and decisive for this term. The site-II mutants are catalytically competent flap endonucleases, so the activity is not a contaminant or an artefact of the exonuclease, and isothermal titration calorimetry ties it to occupancy of the single high-affinity metal site. Supporting Evidence: PMID:15077103 Mutation of crucial aspartates in site II abolished exonuclease action, but caused enzymes to retain structure-specific (flap endonuclease) activity. PMID:15077103 Structure-specific endonuclease activity requires binding of a single metal ion in the high-affinity site, whereas exonuclease activity requires that both the high- and low-affinity sites be occupied by divalent cofactor.
GO:0017108 5'-flap endonuclease activity	IDA PMID:17559871 Comparison of the catalytic parameters and reaction specific...	ACCEPT	Summary: Reaction specificity of the phage enzyme measured on flap, nicked, pseudo-Y and 5'-overhanging substrates, with and without a 3'-extrahelical nucleotide. Reason: The paper is a systematic substrate-specificity study of T5 FEN and reports endonucleolytic cleavage of 5'-bifurcated substrates at the single/double-stranded junction, which is the definition of this term. Accepted as a core activity. Supporting Evidence: PMID:17559871 Flap endonucleases (FENs) catalyse the exonucleolytic hydrolysis of blunt-ended duplex DNA substrates and the endonucleolytic cleavage of 5'-bifurcated nucleic acids at the junction formed between single and double-stranded DNA. PMID:17559871 These substrates contained one or more hairpin turns and mimic duplex, 5'-overhanging duplex, pseudo-Y, nicked DNA, and flap structures.
GO:0017108 5'-flap endonuclease activity	IDA PMID:27273516 Direct observation of DNA threading in flap endonuclease com...	ACCEPT	Summary: Crystal structures of the gene D15 product bound to intact flap substrates and to products, with structure-specific nuclease activity detected for the wild type and lost in the active-site variants. Reason: The strongest evidence in the set and the only cited paper whose full text is available: the substrate's single-stranded 5' arm is caught threading through the helical arch into the active site, and dual-labelled-substrate assays detect structure-specific cleavage in wild type but not in the D153K and D155K variants. The paper states explicitly that its T5Fen is the gene D15 product. Supporting Evidence: PMID:27273516 They reveal single-stranded DNA threading through a hole in the enzyme, which is enclosed by an inverted V-shaped helical arch straddling the active site. PMID:27273516 Structure-specific nuclease activity was readily detected using a dual labelled substrate
GO:0017108 5'-flap endonuclease activity	IDA PMID:9874768 Mutagenesis of conserved lysine residues in bacteriophage T5...	ACCEPT	Summary: Flap cleavage by wild-type and lysine-mutant enzyme, with different pH optima from the exonuclease reaction, indicating separate mechanisms for the two activities. Reason: Direct assay on flap structures, and the K83A result makes the flap endonuclease activity independently assayable: the mutant has no exonuclease activity yet cleaves flaps normally. Core activity, correct term. Supporting Evidence: PMID:9874768 Biochemical analysis demonstrated that K83 is absolutely required for exonucleolytic activity on single-stranded DNA but is not required for endonucleolytic cleavage of flap structures. PMID:9874768 The wild-type protein has different pH optima for endonuclease and exonuclease activities.
GO:0017108 5'-flap endonuclease activity	IEA GO_REF:0000120	ACCEPT	Summary: UniRule/InterPro propagation of the FEN signature to the same activity that four IDA rows establish experimentally for this protein. Reason: The mapping is correct and lands on the right term. IPR038969 (FEN) and HAMAP-Rule MF_04140 were built around this and related 5'-nucleases, and the activity they predict is directly demonstrated for D15 itself, so there is no propagation concern; the rows reinforce each other. Supporting Evidence: file:BPT5/D15/D15-uniprot.txt Catalyzes both the 5'-exonucleolytic and structure-specific endonucleolytic hydrolysis of DNA branched nucleic acid molecules PMID:15077103 Mutation of crucial aspartates in site II abolished exonuclease action, but caused enzymes to retain structure-specific (flap endonuclease) activity.
GO:0019034 viral replication complex	IMP PMID:6248541 Isolation and characterization of a putative bacteriophage T...	KEEP AS NON CORE	Summary: CACAO row. The cited paper isolates a large (about 5 MDa) assembly from T5-infected E. coli containing host RNA polymerase together with the phage proteins gpC2, gpD9 (DNA polymerase), gpD5 and gpD15, and infers that transcription and replication are integrated in infected cells. The term matches what the paper claims, which is membership of a replication-associated structure; the authors themselves call the complex putative. Reason: What the paper actually shows for this gene: gpD15 co-purifies through the fractionation with the other components, and the abstract names it as one of two phage proteins essential for T5 DNA replication and for initiation of late transcription. GO:0019034 is defined loosely enough ("Specific locations and structures in the virus infected cell involved in replicating the viral genome") that a replication-associated assembly qualifies, so the CACAO term is not too downstream and not the wrong granularity. It is kept but not as a core function, for three reasons: the evidence is a single crude co-isolation from 1980 with no stoichiometry, reconstitution or independent confirmation that could be found; the authors hedge it as putative; and this protein's established biology is its enzymology, which does not depend on complex membership. No REMOVE: the paper is about this protein among others, the full text is not in the cache (full_text_available: false; PMC515921-era scans give no machine-readable text), and the GONUTS wiki page for this PMID, which would record the student's evidence, returned only the site's offline notice when queried on 2026-10-29. The one clear defect is the evidence code, recorded in source_defects: IMP denotes a mutant phenotype, while this is a biochemical co-isolation (IDA, or IPI for the interaction reading). Supporting Evidence: PMID:6248541 A well defined enzyme comples of approximately 5 X 10(6) daltons that contains phage and host cell components known to be required for the processes of phage transcription and DNA replication has been isolated from bacteriophage T5-infected Escherichia coli cells. PMID:6248541 the proteins gpD5 (DNA-binding protein), and gpD15 (nuclease) which are both known to be essential for T5 DNA replication and for the initiation of late transcription PMID:6248541 The composition of the enzyme complex suggests that the processes of transcription and replication are integrated in T5-infected cells.
GO:0019086 late viral transcription	IMP PMID:4357874 Requirement of a phage-induced 5'-exonuclease for the expres...	MARK AS OVER ANNOTATED	Summary: CACAO row. The cited paper shows that T5 amber mutants in gene D15 make early proteins normally but virtually no late proteins, and proposes that late transcription requires gaps or nicks introduced into T5 DNA. The term asserts that D15 participates in late viral transcription itself, which is one step further than the data or the authors' own model support. Reason: What the paper shows for this gene: SDS-PAGE of proteins induced in a nonpermissive host by a D15 amber mutant shows a virtual absence of late proteins while the early enzyme deoxyribonucleoside monophosphokinase is made at wild-type levels, and lysozyme and serum-blocking power are very low. That establishes that D15 activity is necessary for late gene expression. It does not establish participation: GO:0019086 is the transcription of the final group of viral genes, carried out by host RNA polymerase under the control of the phage gpC2 element, whereas the authors attribute the requirement to a DNA-processing step performed by the nuclease ("the introduction of gaps or nicks in the T5 DNA so that late transcription can occur"). This is the project's phenotype-read-as-process shape: a downstream genetic requirement annotated as the process, where the gene product performs none of its steps. Kept and flagged rather than removed, per the curator-deference rule: the row is experimental, the cached record is abstract-only (PMC427268 holds page scans and returns no text), and GONUTS was offline on 2026-10-29, so the full text may contain transcription assays the abstract does not mention. The faithful representation is the nuclease activity plus a causal link upstream of late transcription in a GO-CAM, or at most a regulation term (GO:0046782 or GO:0050434) if a direct effect on transcription were demonstrated; a bare involved_in on the transcription term asserts the wrong participant. Supporting Evidence: PMID:4357874 Amber mutants of bacteriophage T5 defective in gene D15, which codes for a 5'-exonuclease, do not express late genes. PMID:4357874 Synthesis of lysozyme and serum-blocking power is very low whereas the extent of synthesis of an early enzyme, deoxyribonucleoside monophosphokinase, is similar to that in wild-type infections. PMID:4357874 It is proposed that one requirement for the expression of late T5 genes is the introduction of gaps or nicks in the T5 DNA so that late transcription can occur.
GO:0033567 DNA replication, Okazaki fragment processing	IEA GO_REF:0000120	MARK AS OVER ANNOTATED	Summary: UniRule/HAMAP propagation of the canonical FEN1 role in lagging-strand maturation. The molecular capability is right, but no study of T5 shows D15 processing Okazaki flaps during phage replication, and UniProt itself states the role only as a possibility. Reason: This is the reagent-and-paralogy framing reaching a phage protein: the family term is written around eukaryotic and bacterial lagging-strand maturation, and the HAMAP rule carries it to every FEN. For D15 the evidence is substrate specificity in vitro plus the genetic requirement for T5 DNA replication; what the nuclease does in the infected cell is better described by its documented role in maturing replicated concatemers (PMID:904023) than by Okazaki fragment processing, which is not assayed anywhere in the T5 literature read for this review. UniProt's own wording is hedged. Kept rather than removed, since the activity is exactly the one the term presupposes and lagging-strand synthesis does occur in T5 replication; flagged so that the inference is not read as a T5 observation. Supporting Evidence: file:BPT5/D15/D15-uniprot.txt This function may be used for example to trim such branched molecules generated by Okazaki fragments synthesis during replication. PMID:27273516 Flap endonucleases are essential enzymes that trim such branched molecules generated by Okazaki-fragment synthesis during replication.
GO:0035312 5'-3' DNA exonuclease activity	IMP PMID:9874768 Mutagenesis of conserved lysine residues in bacteriophage T5...	ACCEPT	Summary: CACAO row, and the best-chosen of the four. Site-directed mutagenesis of K83, K196 and K215 shows that K83 is absolutely required for 5'-3' exonucleolytic activity on single-stranded DNA while flap endonucleolysis is unaffected; the crystal structure of the mutant shows the active site is undisturbed, so the loss is of the exonuclease function specifically. Reason: What the paper shows for this gene matches the term precisely, and the evidence code fits: the assertion rests on the phenotype of defined point mutants of this protein (IMP), not on the wild-type assay alone. The granularity is also right and is not redundant against the seven GO:0051908 rows: GO:0051908 is restricted to double-stranded substrates, whereas the activity whose loss defines K83A is on single-stranded DNA, and GO:0035312 is the term that covers DNA of either strand form while still stating the 5'-3' direction. This is the term the two generic ancestors in this review (GO:0004529, GO:0008409) are modified to. Supporting Evidence: PMID:9874768 Biochemical analysis demonstrated that K83 is absolutely required for exonucleolytic activity on single-stranded DNA but is not required for endonucleolytic cleavage of flap structures. PMID:9874768 Structural analysis of this mutant by x-ray crystallography showed no significant perturbations around the metal-binding sites in the active site. file:BPT5/D15/D15-uniprot.txt K->A: No exonuclease activity, retains full endonuclease activity on a flap structure.
GO:0039693 viral DNA genome replication	IEA GO_REF:0000120	ACCEPT	Summary: Replication of the T5 genome is the process in which this nuclease acts: it is an early protein, it is genetically essential for T5 DNA replication, and the step it performs is the nucleolytic processing of branched and interrupted replication intermediates. Reason: Although the row arrives by keyword propagation, the claim is supported for T5 itself and the participation test is satisfied: the protein performs a catalytic step on replication intermediates rather than merely being required for the outcome. D15 amber mutants are replication-defective (PMID:6248541 states gpD15 is known to be essential for T5 DNA replication), and the conversion of replicated concatemeric T5 DNA into the single-stranded fragments found in mature virion DNA requires a functional D15 nuclease (PMID:904023). Core process for this gene. Supporting Evidence: PMID:6248541 the proteins gpD5 (DNA-binding protein), and gpD15 (nuclease) which are both known to be essential for T5 DNA replication and for the initiation of late transcription PMID:904023 the subsequent formation of the single-stranded fragments does require that the D15 nuclease be functional file:BPT5/D15/D15-uniprot.txt Expressed in the early phase of the viral replicative cycle.
GO:0046872 metal ion binding	IEA GO_REF:0000120	MODIFY	Summary: Metal binding is correct and functionally central, and the identities of the metals are known: catalytic magnesium ions in the two active-site clusters and a structural potassium ion in the H3TH DNA-binding motif. Reason: The keyword maps to the root metal-binding term, while the structures resolve the ligands: two Mg2+ ions in Cat1 and a third in Cat2 of the wild-type enzyme, and a K+ ion coordinated by backbone carbonyls of the helix-three-turn-helix motif that contacts the duplex (PMID:27273516). Calorimetry and site mutants define two divalent sites of different affinity whose occupancy selects the endo- or exonucleolytic reaction (PMID:15077103). GO:0000287 and GO:0030955 are is_a descendants of GO:0046872 and state what is actually known. Proposed replacements: magnesium ion binding potassium ion binding Supporting Evidence: file:BPT5/D15/D15-uniprot.txt Binds divalent metal cations, probably Mg(2+). PMID:27273516 A potassium ion was bound via backbone carbonyl oxygens within this motif. PMID:15077103 Isothermal titration calorimetry revealed that site I has a 30-fold higher affinity for cofactor than site II.
GO:0048256 flap endonuclease activity	IEA GO_REF:0000002	MODIFY	Summary: InterPro2GO mapping of the D15-like FEN signature onto the parent flap-endonuclease term, where the gene already carries the specific 5'-flap child. Reason: GO:0017108 5'-flap endonuclease activity is an is_a descendant of GO:0048256, is asserted by four IDA rows here and is accepted, so the parent adds nothing; and its definition ("Catalysis of the cleavage of a flap structure in DNA, but not other DNA structures") fits this enzyme poorly, since D15 also cleaves 5'-overhangs and pseudo-Y junctions and degrades DNA exonucleolytically from a blunt end. Refined to the child rather than kept. Proposed replacements: 5'-flap endonuclease activity Supporting Evidence: PMID:17559871 These substrates contained one or more hairpin turns and mimic duplex, 5'-overhanging duplex, pseudo-Y, nicked DNA, and flap structures. file:BPT5/D15/D15-uniprot.txt Active on flap (branched duplex DNA containing a free single-stranded 5'-end), 5'overhangs and pseudo-Y structures
GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity	EXP PMID:10364212 Variation in the steady state kinetic parameters of wild typ...	ACCEPT	Summary: Steady-state parameters of the 5'-3' exonuclease reaction as a function of pH, establishing the catalytic properties of the wild-type enzyme and the role of Lys-83 protonation in substrate binding. Reason: Core activity and correct term: this is the EC 3.1.11.3 reaction for which UniProt cites this paper with ECO:0000269. The term's duplex restriction is appropriate here, and the complementary single-stranded activity is covered by the accepted GO:0035312 row. Supporting Evidence: PMID:10364212 T5 5'-3'-exonuclease is a member of a family of homologous 5'-nucleases essential for DNA replication and repair. PMID:10364212 We therefore conclude that protonation of Lys-83 in the wild type protein facilitates DNA binding.
GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity	EXP PMID:17559871 Comparison of the catalytic parameters and reaction specific...	ACCEPT	Summary: Exonucleolytic hydrolysis of blunt-ended duplex substrates measured directly for the T5 enzyme alongside an archaeal FEN. Reason: The paper assays precisely the activity the term names, on duplex DNA, and reports the phage enzyme to be rate-limited by product release across the substrate panel. Core activity. Supporting Evidence: PMID:17559871 Flap endonucleases (FENs) catalyse the exonucleolytic hydrolysis of blunt-ended duplex DNA substrates and the endonucleolytic cleavage of 5'-bifurcated nucleic acids at the junction formed between single and double-stranded DNA. PMID:17559871 Steady-state and pre-steady-state catalytic parameters reveal that the phage enzyme is rate-limited by product release with all the substrates tested.
GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity	EXP PMID:2211703 Properties of overexpressed phage T5 D15 exonuclease. Simila...	ACCEPT	Summary: Homogeneous overexpressed D15 degrades native (duplex) and heat-denatured DNA, with a mode of action like the 5'-3' exonuclease of E. coli DNA polymerase I. Reason: The founding biochemical characterisation of this protein and the basis of its EC 3.1.11.3 assignment in UniProt. Activity on native DNA is the duplex case the term specifies. Core activity. Supporting Evidence: PMID:2211703 The purified enzyme is active on both native and heat-denatured DNA and shows no endonuclease activity on either double-stranded closed-circular or nicked DNA. file:BPT5/D15/D15-uniprot.txt Reaction=Exonucleolytic cleavage in the 5'- to 3'-direction to yield
GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity	EXP PMID:27273516 Direct observation of DNA threading in flap endonuclease com...	ACCEPT	Summary: Structures of substrate and product complexes with the catalytic metal ions, plus activity assays in which the wild-type enzyme digests DNA and the catalytic-aspartate variants do not. Reason: Core activity, with the mechanism resolved: the paper follows the reaction from free enzyme through pre-threading and fully threaded intermediates to a pseudo-product complex, and shows loss of all hydrolytic activity in D153K and D155K. Full text available and read for this review. Supporting Evidence: PMID:27273516 neither variant T5FenD153K nor a second variant, D155K, showed activity PMID:27273516 We have shown a series of snapshots in the FEN-catalyzed hydrolysis reaction from free enzyme to pseudo-product complex via pre-threading and fully threaded intermediates.
GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity	EXP PMID:9380501 Structure-specific DNA binding by bacteriophage T5 5'-->3' e...	ACCEPT	Summary: The paper's starting characterisation of the protein as a 5'-3' exodeoxyribonuclease, together with catalytic comparisons of wild-type and cysteine-substituted enzyme. Reason: Correct term for the activity assayed, and the paper adds the information that catalysis requires a divalent metal cofactor (binding was measured in its absence precisely to separate the two). Core activity. Supporting Evidence: PMID:9380501 Phage T5 exonuclease is a 5'-->3'exodeoxyribonuclease that also exhibits endonucleolytic activity on flap structures (branched duplex DNA containing a free single-stranded 5'-end). PMID:9380501 The binding of T5 exonuclease to various structures was investigated using native electrophoretic mobility shift assays (EMSA) in the absence of the essential divalent metal cofactor.
GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity	EXP PMID:9874768 Mutagenesis of conserved lysine residues in bacteriophage T5...	ACCEPT	Summary: Exonucleolytic activity of wild-type and lysine-mutant enzyme, with the exonuclease reaction separable from flap endonucleolysis by mutation and by pH. Reason: Core activity. The paper's framing statement and its assays both concern the 5'-3' exonuclease, and the mutational dissection is what establishes that the two activities are mechanistically distinct rather than one being a special case of the other. Supporting Evidence: PMID:9874768 Efficient cellular DNA replication requires the activity of a 5'-3' exonuclease. PMID:9874768 The wild-type protein has different pH optima for endonuclease and exonuclease activities.
GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity	EXP PMID:9889266 A single cleavage assay for T5 5'-->3' exonuclease: determin...	ACCEPT	Summary: Single-cleavage assay on a 5'-overhanging hairpin substrate giving the catalytic parameters of the wild-type enzyme and of three lysine mutants, with products identified by mass spectrometry. Reason: Core activity, quantified: the enzyme accelerates cleavage of a specific phosphodiester bond by at least 10^15, and all three lysines contribute to ground state substrate binding. Correct term for the reaction assayed. Supporting Evidence: PMID:9889266 Here, we report the development of a structure-specific single cleavage assay for this enzyme which uses a 5'-overhanging hairpin substrate. PMID:9889266 The 5'-nucleases have both exonucleolytic and structure-specific endo-nucleolytic DNA cleavage activity and are conserved in organisms as diverse as bacteriophage and mammals.
GO:0051908 double-stranded DNA 5'-3' DNA exonuclease activity	IEA GO_REF:0000003	ACCEPT	Summary: EC 3.1.11.3 to GO mapping. The EC number is itself experimentally assigned to this protein by UniProt from six primary papers, so the mapping is sound. Reason: Unlike many EC-derived IEA rows, this one does not rest on an inferred EC number: UniProt's catalytic-activity statement for P06229 carries ECO:0000269 citations to PubMed 2211703, 9380501, 9874768, 9889266, 10364212, 17559871 and 27273516, and the reaction written there is the one GO:0051908 names. Consistent with the seven EXP rows for the same term. Supporting Evidence: file:BPT5/D15/D15-uniprot.txt Reaction=Exonucleolytic cleavage in the 5'- to 3'-direction to yield PMID:2211703 The purified enzyme is active on both native and heat-denatured DNA and shows no endonuclease activity on either double-stranded closed-circular or nicked DNA.
GO:0140097 catalytic activity, acting on DNA	IEA GO_REF:0000117	TOO GENERAL	Summary: ARBA association rule placing the protein among DNA-acting catalysts; true, and entailed several levels up from the specific activities accepted here. Reason: GO:0140097 is an ancestor of both GO:0051908 and GO:0017108, which are accepted in this review on direct evidence, so the row is redundant. Scored on the claim, not on the fact that the source is a machine-learned rule; the claim itself is not in doubt. Supporting Evidence: PMID:17559871 Flap endonucleases (FENs) catalyse the exonucleolytic hydrolysis of blunt-ended duplex DNA substrates and the endonucleolytic cleavage of 5'-bifurcated nucleic acids at the junction formed between single and double-stranded DNA.
GO:1990238 double-stranded DNA endonuclease activity	IDA PMID:904023 Role of the T5 gene D15 nuclease in the generation of nicked...	MODIFY	Summary: CACAO row. The cited paper re-examines purified D15 nuclease and reports that, besides acting as a 5'-3' exonuclease, it introduces endonucleolytic scissions into mature T5 DNA in a reaction requiring duplex DNA and pre-existing single-stranded interruptions. The assay is on this protein and the paper is about this gene, but the term states the weakest, structure-blind version of the finding. Reason: What the paper shows for this gene is an endonucleolytic cut in a duplex that already carries a single-strand interruption, i.e. the structure-specific reaction of a 5'-nuclease on a nicked or flapped junction, which is GO:0017108. GO:1990238 sits on a different branch (under GO:0004520, not under GO:0048256) and carries no structural requirement, so it reads as general duplex cleavage: that reading is contradicted by Sayers and Eckstein, who found no endonuclease activity of homogeneous D15 on closed-circular or nicked duplex DNA (PMID:2211703), and by the substrate requirement UniProt records, a free single-stranded 5' end. The two reports are reconcilable only if the activity is structure-specific, which is what the replacement term says. This is a granularity failure, not a false claim or a mis-attributed paper, so MODIFY rather than REMOVE, and the curator-deference rule applies anyway: the cached record is abstract-only (PMC515921 returns page scans with no text) and GONUTS was offline on 2026-10-29. Proposed replacements: 5'-flap endonuclease activity Supporting Evidence: PMID:904023 the enzyme can also introduce endonucleolytic scissions into mature T5 DNA in a reaction that requires duplex T5 DNA and preexisting, single-stranded interruptions PMID:2211703 The purified enzyme is active on both native and heat-denatured DNA and shows no endonuclease activity on either double-stranded closed-circular or nicked DNA. file:BPT5/D15/D15-uniprot.txt The substrates require a free, single-stranded 5' end, with endonucleolytic hydrolysis occurring at the junction of double- and single-stranded DNA

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