{"gene":"NTMT2","run_date":"2026-06-10T05:19:52","timeline":{"discoveries":[{"year":2013,"finding":"NTMT2 (METTL11B/NRMT2) is an N-terminal monomethylase that recognizes the same N-terminal consensus sequences as NTMT1 (NRMT1), but unlike NTMT1 (which can mono-, di-, and tri-methylate substrates), NTMT2 is primarily a monomethylase. Concurrent expression of both enzymes accelerates trimethylation production, indicating NTMT2 primes substrates for subsequent trimethylation by NTMT1.","method":"Enzyme activity assays and mass spectrometry experiments comparing catalytic functions of NTMT1 and NTMT2 in vitro","journal":"The Biochemical Journal","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assays combined with mass spectrometry, multiple orthogonal methods in a single focused study","pmids":["24090352"],"is_preprint":false},{"year":2013,"finding":"NTMT2 shares similar tissue expression and cellular localization patterns with NTMT1, as determined by direct experimental comparison.","method":"Tissue expression profiling and cellular localization experiments (direct comparison between NTMT1 and NTMT2)","journal":"The Biochemical Journal","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — localization and expression comparison reported in a focused mechanistic study, but no functional consequence of localization explicitly demonstrated","pmids":["24090352"],"is_preprint":false},{"year":2023,"finding":"NTMT2 (METTL11B) acts as an activator of NTMT1 (METTL11A) through direct complex formation. Co-immunoprecipitation and in vitro methylation assays confirm that NTMT2 binding increases NTMT1 activity, and this regulatory effect is noncatalytic (catalytic activity of NTMT2 is not required for activation of NTMT1).","method":"Co-immunoprecipitation, mass spectrometry, and in vitro methylation assays; catalytic-dead mutant analysis","journal":"The Journal of Biological Chemistry","confidence":"High","confidence_rationale":"Tier 1–2 / Moderate — reciprocal Co-IP plus in vitro methylation assays plus mutagenesis demonstrating noncatalytic function, multiple orthogonal methods in a single focused study","pmids":["36889590"],"is_preprint":false},{"year":2023,"finding":"NTMT2 (METTL11B), NTMT1 (METTL11A), and METTL13 can form a trimeric complex. When all three are present, the inhibitory regulatory effects of METTL13 on NTMT1 activity take precedence over the activating effects of NTMT2.","method":"Co-immunoprecipitation and in vitro methylation assays with combinations of all three proteins","journal":"The Journal of Biological Chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP and functional methylation assays in a single lab, two orthogonal methods","pmids":["36889590"],"is_preprint":false},{"year":2023,"finding":"NTMT2 (METTL11B) has no proven in vivo substrates or predicted targets that are not also methylated by NTMT1 (METTL11A), suggesting its primary biological role may be noncatalytic (regulatory).","method":"Review and synthesis of substrate identification experiments, with no exclusive in vivo NTMT2 substrate identified","journal":"Journal of Cell Science","confidence":"Low","confidence_rationale":"Tier 3 / Weak — synthesis/review conclusion based on negative substrate identification results from prior experiments; no new direct experiment","pmids":["36647772"],"is_preprint":false},{"year":2023,"finding":"Non-radioactive in vitro assays (Western blots with full-length recombinant substrates and luminescent assays with peptide substrates) can be used to verify substrates of NTMT2 (METTL11B) and characterize its regulatory interactions with NTMT1 and METTL13.","method":"Western blot and luminescent in vitro methyltransferase assays with recombinant proteins and peptide substrates","journal":"Methods in Enzymology","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — validated methodological approach for NTMT2 activity, single lab, focused on assay development rather than novel mechanistic discovery","pmids":["37230594"],"is_preprint":false},{"year":2020,"finding":"The bisubstrate analogue inhibitor with a 4-C linker shows more than 3000-fold selectivity for NTMT1 over its homologue NTMT2, demonstrating distinct active-site properties between NTMT1 and NTMT2.","method":"In vitro enzyme inhibition assays with bisubstrate analogues comparing Ki,app for NTMT1 versus NTMT2","journal":"Journal of Medicinal Chemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical assay with defined inhibitors, single lab, selectivity result incidental to primary NTMT1 study","pmids":["32605369"],"is_preprint":false}],"current_model":"NTMT2 (METTL11B/NRMT2) is an N-terminal α-amine monomethylase that recognizes the same consensus sequences as its paralog NTMT1, but primarily installs only a single methyl group; it also forms a direct complex with NTMT1 and activates NTMT1-mediated trimethylation through a noncatalytic mechanism, while a trimeric complex with METTL13 places NTMT2's activating effect subordinate to METTL13's inhibitory regulation of NTMT1."},"narrative":{"mechanistic_narrative":"NTMT2 (METTL11B/NRMT2) is a protein N-terminal α-amine methyltransferase that functions in the same N-terminal methylation pathway as its paralog NTMT1, recognizing the same N-terminal consensus sequences but acting primarily as a monomethylase rather than installing the full di- and tri-methyl marks [PMID:24090352]. Co-expression of both enzymes accelerates trimethylation, indicating that NTMT2 primes substrates for subsequent trimethylation by NTMT1 [PMID:24090352]. Beyond this catalytic priming, NTMT2 acts as a noncatalytic activator of NTMT1 through direct complex formation: binding increases NTMT1 activity even when NTMT2's own catalytic activity is abolished [PMID:36889590]. This regulatory role is embedded in a higher-order assembly, since NTMT2, NTMT1, and METTL13 can form a trimeric complex in which the inhibitory effect of METTL13 on NTMT1 takes precedence over NTMT2's activating effect [PMID:36889590]. NTMT1 and NTMT2 have distinct active-site properties, as a bisubstrate-analogue inhibitor shows >3000-fold selectivity for NTMT1 over NTMT2 [PMID:32605369]. No NTMT2-exclusive in vivo substrate has been identified in the available corpus, consistent with a primary regulatory rather than independent catalytic function [PMID:36647772].","teleology":[{"year":2013,"claim":"Establishing whether NTMT2 is an independent methyltransferase or a distinct activity within the N-terminal methylation pathway showed it is a monomethylase that primes substrates for NTMT1-mediated trimethylation, defining a two-enzyme catalytic relationship.","evidence":"In vitro enzyme activity assays and mass spectrometry comparing NTMT1 and NTMT2 catalytic outputs","pmids":["24090352"],"confidence":"High","gaps":["No in vivo demonstration of sequential priming in cells","Physiological substrates of NTMT2 monomethylation not defined"]},{"year":2013,"claim":"Comparing the tissue expression and subcellular localization of the two paralogs addressed whether NTMT2 could plausibly act on the same substrate pool as NTMT1, finding shared expression and localization patterns.","evidence":"Tissue expression profiling and cellular localization comparison of NTMT1 and NTMT2","pmids":["24090352"],"confidence":"Medium","gaps":["No functional consequence of localization demonstrated","Localization not resolved to a specific compartment in this evidence"]},{"year":2020,"claim":"Whether NTMT1 and NTMT2 have distinguishable active sites was tested with bisubstrate-analogue inhibitors, revealing >3000-fold selectivity for NTMT1 and confirming the paralogs are biochemically distinct enzymes.","evidence":"In vitro enzyme inhibition assays comparing Ki,app for NTMT1 versus NTMT2","pmids":["32605369"],"confidence":"Medium","gaps":["Structural basis of the selectivity not resolved","Result incidental to a primary NTMT1-focused study"]},{"year":2023,"claim":"The question of whether NTMT2 regulates NTMT1 beyond catalytic priming was answered by showing direct complex formation activates NTMT1 in a manner independent of NTMT2's catalytic activity, establishing a noncatalytic regulatory function.","evidence":"Reciprocal co-immunoprecipitation, in vitro methylation assays, and catalytic-dead mutant analysis","pmids":["36889590"],"confidence":"High","gaps":["Structural basis of NTMT2-NTMT1 complex unknown","Cellular conditions controlling complex formation not defined"]},{"year":2023,"claim":"Placing the NTMT2-NTMT1 interaction in a broader regulatory context showed a trimeric complex with METTL13 in which METTL13's inhibition of NTMT1 overrides NTMT2's activation, defining a hierarchy of regulation.","evidence":"Co-immunoprecipitation and in vitro methylation assays with combinations of all three proteins","pmids":["36889590"],"confidence":"Medium","gaps":["Stoichiometry and architecture of the trimeric complex unknown","In vivo relevance and regulation of the hierarchy not established"]},{"year":2023,"claim":"Synthesis of substrate-identification efforts addressed whether NTMT2 has an exclusive catalytic role, concluding no NTMT2-specific in vivo substrate exists and pointing to a primary regulatory function.","evidence":"Review and synthesis of prior substrate identification experiments","pmids":["36647772"],"confidence":"Low","gaps":["Negative-result synthesis, not a new direct experiment","Cannot exclude an undiscovered NTMT2-exclusive substrate"]},{"year":null,"claim":"It remains unknown what physiological signals control assembly of the NTMT2-NTMT1-METTL13 complex and what cellular processes depend on NTMT2's noncatalytic activation of NTMT1.","evidence":"","pmids":[],"confidence":"Low","gaps":["No in vivo phenotype attributed to NTMT2 regulatory function","Structural model of any NTMT2-containing complex absent"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[0]},{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[2,3]}],"localization":[],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0]}],"complexes":["NTMT2-NTMT1 complex","NTMT2-NTMT1-METTL13 trimeric complex"],"partners":["NTMT1","METTL13"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q5VVY1","full_name":"N-terminal Xaa-Pro-Lys N-methyltransferase 2","aliases":["Alpha N-terminal protein methyltransferase 1B","Methyltransferase-like protein 11B","X-Pro-Lys N-terminal protein methyltransferase 1B","NTM1B"],"length_aa":283,"mass_kda":32.4,"function":"Alpha N-methyltransferase that methylates the N-terminus of target proteins containing the N-terminal motif [Ala/Pro/Ser]-Pro-Lys when the initiator Met is cleaved. Specifically catalyzes monomethylation of exposed alpha-amino group of Ala or Ser residue in the [Ala/Ser]-Pro-Lys motif and Pro in the Pro-Pro-Lys motif (PubMed:24090352, PubMed:30417120). Predominantly functions as a mono-methyltransferase but is also able to di-/tri-methylate the GPKRIA peptide and di-methylate the PPKRIA peptide (in vitro) (PubMed:30417120). May activate NTMT1 by priming its substrates for trimethylation (PubMed:24090352)","subcellular_location":"Nucleus","url":"https://www.uniprot.org/uniprotkb/Q5VVY1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/NTMT2","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/NTMT2","total_profiled":1310},"omim":[],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"heart muscle","ntpm":1.6}],"url":"https://www.proteinatlas.org/search/NTMT2"},"hgnc":{"alias_symbol":["HOMT1B"],"prev_symbol":["C1orf184","METTL11B"]},"alphafold":{"accession":"Q5VVY1","domains":[{"cath_id":"-","chopping":"1-59","consensus_level":"medium","plddt":80.2966,"start":1,"end":59},{"cath_id":"3.40.50.150","chopping":"84-278","consensus_level":"high","plddt":96.5117,"start":84,"end":278}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VVY1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VVY1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q5VVY1-F1-predicted_aligned_error_v6.png","plddt_mean":90.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=NTMT2","jax_strain_url":"https://www.jax.org/strain/search?query=NTMT2"},"sequence":{"accession":"Q5VVY1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q5VVY1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q5VVY1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q5VVY1"}},"corpus_meta":[{"pmid":"29050564","id":"PMC_29050564","title":"A Missense Variant in PLEC Increases Risk of Atrial Fibrillation.","date":"2017","source":"Journal of the American College of Cardiology","url":"https://pubmed.ncbi.nlm.nih.gov/29050564","citation_count":67,"is_preprint":false},{"pmid":"24090352","id":"PMC_24090352","title":"NRMT2 is an N-terminal monomethylase that primes for its homologue NRMT1.","date":"2013","source":"The Biochemical journal","url":"https://pubmed.ncbi.nlm.nih.gov/24090352","citation_count":40,"is_preprint":false},{"pmid":"28604785","id":"PMC_28604785","title":"Genome-wide association analysis and functional annotation of positional candidate genes for feed conversion efficiency and growth rate in pigs.","date":"2017","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/28604785","citation_count":33,"is_preprint":false},{"pmid":"32605369","id":"PMC_32605369","title":"Probing the Plasticity in the Active Site of Protein N-terminal Methyltransferase 1 Using Bisubstrate Analogues.","date":"2020","source":"Journal of medicinal chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/32605369","citation_count":24,"is_preprint":false},{"pmid":"32615730","id":"PMC_32615730","title":"Transformation of Mature Osteoblasts into Bone Lining Cells and RNA Sequencing-Based Transcriptome Profiling of Mouse Bone during Mechanical Unloading.","date":"2020","source":"Endocrinology and metabolism (Seoul, Korea)","url":"https://pubmed.ncbi.nlm.nih.gov/32615730","citation_count":14,"is_preprint":false},{"pmid":"34870779","id":"PMC_34870779","title":"Association of DNA methylation and transcriptome reveals epigenetic etiology of heart failure.","date":"2021","source":"Functional & integrative genomics","url":"https://pubmed.ncbi.nlm.nih.gov/34870779","citation_count":12,"is_preprint":false},{"pmid":"36889590","id":"PMC_36889590","title":"Opposing regulation of the Nα-trimethylase METTL11A by its family members METTL11B and METTL13.","date":"2023","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/36889590","citation_count":10,"is_preprint":false},{"pmid":"35044082","id":"PMC_35044082","title":"Identification of a glioma functional network from gene fitness data using machine learning.","date":"2022","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35044082","citation_count":7,"is_preprint":false},{"pmid":"36647772","id":"PMC_36647772","title":"Three's a crowd - why did three N-terminal methyltransferases evolve for one job?","date":"2023","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/36647772","citation_count":6,"is_preprint":false},{"pmid":"37107639","id":"PMC_37107639","title":"Identification of Key Functional Genes and LncRNAs Influencing Muscle Growth and Development in Leizhou Black Goats.","date":"2023","source":"Genes","url":"https://pubmed.ncbi.nlm.nih.gov/37107639","citation_count":6,"is_preprint":false},{"pmid":"37230594","id":"PMC_37230594","title":"Optimizing purification and activity assays of N-terminal methyltransferase complexes.","date":"2023","source":"Methods in enzymology","url":"https://pubmed.ncbi.nlm.nih.gov/37230594","citation_count":0,"is_preprint":false},{"pmid":"41339727","id":"PMC_41339727","title":"AI-derived five-gene signature predicts risk in multiple myeloma under bortezomib-based therapy.","date":"2025","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/41339727","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7911,"output_tokens":1656,"usd":0.024286,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":8420,"output_tokens":2292,"usd":0.0497,"stage2_stop_reason":"end_turn"},"total_usd":0.073986,"stage1_batch_id":"msgbatch_013a8chtv3AWyTqv4z4sEF4C","stage2_batch_id":"msgbatch_01AHsuW63vinsvuTgzmQ3n62","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2013,\n      \"finding\": \"NTMT2 (METTL11B/NRMT2) is an N-terminal monomethylase that recognizes the same N-terminal consensus sequences as NTMT1 (NRMT1), but unlike NTMT1 (which can mono-, di-, and tri-methylate substrates), NTMT2 is primarily a monomethylase. Concurrent expression of both enzymes accelerates trimethylation production, indicating NTMT2 primes substrates for subsequent trimethylation by NTMT1.\",\n      \"method\": \"Enzyme activity assays and mass spectrometry experiments comparing catalytic functions of NTMT1 and NTMT2 in vitro\",\n      \"journal\": \"The Biochemical Journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assays combined with mass spectrometry, multiple orthogonal methods in a single focused study\",\n      \"pmids\": [\"24090352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"NTMT2 shares similar tissue expression and cellular localization patterns with NTMT1, as determined by direct experimental comparison.\",\n      \"method\": \"Tissue expression profiling and cellular localization experiments (direct comparison between NTMT1 and NTMT2)\",\n      \"journal\": \"The Biochemical Journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — localization and expression comparison reported in a focused mechanistic study, but no functional consequence of localization explicitly demonstrated\",\n      \"pmids\": [\"24090352\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NTMT2 (METTL11B) acts as an activator of NTMT1 (METTL11A) through direct complex formation. Co-immunoprecipitation and in vitro methylation assays confirm that NTMT2 binding increases NTMT1 activity, and this regulatory effect is noncatalytic (catalytic activity of NTMT2 is not required for activation of NTMT1).\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, and in vitro methylation assays; catalytic-dead mutant analysis\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 / Moderate — reciprocal Co-IP plus in vitro methylation assays plus mutagenesis demonstrating noncatalytic function, multiple orthogonal methods in a single focused study\",\n      \"pmids\": [\"36889590\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NTMT2 (METTL11B), NTMT1 (METTL11A), and METTL13 can form a trimeric complex. When all three are present, the inhibitory regulatory effects of METTL13 on NTMT1 activity take precedence over the activating effects of NTMT2.\",\n      \"method\": \"Co-immunoprecipitation and in vitro methylation assays with combinations of all three proteins\",\n      \"journal\": \"The Journal of Biological Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP and functional methylation assays in a single lab, two orthogonal methods\",\n      \"pmids\": [\"36889590\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"NTMT2 (METTL11B) has no proven in vivo substrates or predicted targets that are not also methylated by NTMT1 (METTL11A), suggesting its primary biological role may be noncatalytic (regulatory).\",\n      \"method\": \"Review and synthesis of substrate identification experiments, with no exclusive in vivo NTMT2 substrate identified\",\n      \"journal\": \"Journal of Cell Science\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — synthesis/review conclusion based on negative substrate identification results from prior experiments; no new direct experiment\",\n      \"pmids\": [\"36647772\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Non-radioactive in vitro assays (Western blots with full-length recombinant substrates and luminescent assays with peptide substrates) can be used to verify substrates of NTMT2 (METTL11B) and characterize its regulatory interactions with NTMT1 and METTL13.\",\n      \"method\": \"Western blot and luminescent in vitro methyltransferase assays with recombinant proteins and peptide substrates\",\n      \"journal\": \"Methods in Enzymology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — validated methodological approach for NTMT2 activity, single lab, focused on assay development rather than novel mechanistic discovery\",\n      \"pmids\": [\"37230594\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The bisubstrate analogue inhibitor with a 4-C linker shows more than 3000-fold selectivity for NTMT1 over its homologue NTMT2, demonstrating distinct active-site properties between NTMT1 and NTMT2.\",\n      \"method\": \"In vitro enzyme inhibition assays with bisubstrate analogues comparing Ki,app for NTMT1 versus NTMT2\",\n      \"journal\": \"Journal of Medicinal Chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical assay with defined inhibitors, single lab, selectivity result incidental to primary NTMT1 study\",\n      \"pmids\": [\"32605369\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"NTMT2 (METTL11B/NRMT2) is an N-terminal α-amine monomethylase that recognizes the same consensus sequences as its paralog NTMT1, but primarily installs only a single methyl group; it also forms a direct complex with NTMT1 and activates NTMT1-mediated trimethylation through a noncatalytic mechanism, while a trimeric complex with METTL13 places NTMT2's activating effect subordinate to METTL13's inhibitory regulation of NTMT1.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"NTMT2 (METTL11B/NRMT2) is a protein N-terminal \\u03b1-amine methyltransferase that functions in the same N-terminal methylation pathway as its paralog NTMT1, recognizing the same N-terminal consensus sequences but acting primarily as a monomethylase rather than installing the full di- and tri-methyl marks [#0]. Co-expression of both enzymes accelerates trimethylation, indicating that NTMT2 primes substrates for subsequent trimethylation by NTMT1 [#0]. Beyond this catalytic priming, NTMT2 acts as a noncatalytic activator of NTMT1 through direct complex formation: binding increases NTMT1 activity even when NTMT2's own catalytic activity is abolished [#2]. This regulatory role is embedded in a higher-order assembly, since NTMT2, NTMT1, and METTL13 can form a trimeric complex in which the inhibitory effect of METTL13 on NTMT1 takes precedence over NTMT2's activating effect [#3]. NTMT1 and NTMT2 have distinct active-site properties, as a bisubstrate-analogue inhibitor shows >3000-fold selectivity for NTMT1 over NTMT2 [#6]. No NTMT2-exclusive in vivo substrate has been identified in the available corpus, consistent with a primary regulatory rather than independent catalytic function [#4].\",\n  \"teleology\": [\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing whether NTMT2 is an independent methyltransferase or a distinct activity within the N-terminal methylation pathway showed it is a monomethylase that primes substrates for NTMT1-mediated trimethylation, defining a two-enzyme catalytic relationship.\",\n      \"evidence\": \"In vitro enzyme activity assays and mass spectrometry comparing NTMT1 and NTMT2 catalytic outputs\",\n      \"pmids\": [\"24090352\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No in vivo demonstration of sequential priming in cells\", \"Physiological substrates of NTMT2 monomethylation not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Comparing the tissue expression and subcellular localization of the two paralogs addressed whether NTMT2 could plausibly act on the same substrate pool as NTMT1, finding shared expression and localization patterns.\",\n      \"evidence\": \"Tissue expression profiling and cellular localization comparison of NTMT1 and NTMT2\",\n      \"pmids\": [\"24090352\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No functional consequence of localization demonstrated\", \"Localization not resolved to a specific compartment in this evidence\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Whether NTMT1 and NTMT2 have distinguishable active sites was tested with bisubstrate-analogue inhibitors, revealing >3000-fold selectivity for NTMT1 and confirming the paralogs are biochemically distinct enzymes.\",\n      \"evidence\": \"In vitro enzyme inhibition assays comparing Ki,app for NTMT1 versus NTMT2\",\n      \"pmids\": [\"32605369\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of the selectivity not resolved\", \"Result incidental to a primary NTMT1-focused study\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"The question of whether NTMT2 regulates NTMT1 beyond catalytic priming was answered by showing direct complex formation activates NTMT1 in a manner independent of NTMT2's catalytic activity, establishing a noncatalytic regulatory function.\",\n      \"evidence\": \"Reciprocal co-immunoprecipitation, in vitro methylation assays, and catalytic-dead mutant analysis\",\n      \"pmids\": [\"36889590\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of NTMT2-NTMT1 complex unknown\", \"Cellular conditions controlling complex formation not defined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Placing the NTMT2-NTMT1 interaction in a broader regulatory context showed a trimeric complex with METTL13 in which METTL13's inhibition of NTMT1 overrides NTMT2's activation, defining a hierarchy of regulation.\",\n      \"evidence\": \"Co-immunoprecipitation and in vitro methylation assays with combinations of all three proteins\",\n      \"pmids\": [\"36889590\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Stoichiometry and architecture of the trimeric complex unknown\", \"In vivo relevance and regulation of the hierarchy not established\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Synthesis of substrate-identification efforts addressed whether NTMT2 has an exclusive catalytic role, concluding no NTMT2-specific in vivo substrate exists and pointing to a primary regulatory function.\",\n      \"evidence\": \"Review and synthesis of prior substrate identification experiments\",\n      \"pmids\": [\"36647772\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Negative-result synthesis, not a new direct experiment\", \"Cannot exclude an undiscovered NTMT2-exclusive substrate\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"It remains unknown what physiological signals control assembly of the NTMT2-NTMT1-METTL13 complex and what cellular processes depend on NTMT2's noncatalytic activation of NTMT1.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No in vivo phenotype attributed to NTMT2 regulatory function\", \"Structural model of any NTMT2-containing complex absent\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [2, 3]}\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"complexes\": [\"NTMT2-NTMT1 complex\", \"NTMT2-NTMT1-METTL13 trimeric complex\"],\n    \"partners\": [\"NTMT1\", \"METTL13\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":3,"faith_total":5,"faith_pct":60.0}}