{"gene":"MRPL36","run_date":"2026-06-10T02:59:51","timeline":{"discoveries":[{"year":2009,"finding":"MRPL36 (mitochondrial ribosomal protein L36) physically associates with LETM1, a mitochondrial inner membrane protein, forming a complex. LETM1 acts as an anchor protein for this interaction. LETM1 overexpression reduces mitochondrial biogenesis and ATP production, and this regulation involves the LETM1-MRPL36 complex.","method":"Co-immunoprecipitation; adenovirus-mediated overexpression with functional readouts (mitochondrial mass, ATP production)","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — reciprocal Co-IP shown but single lab, single study; functional link established by overexpression only","pmids":["19318571"],"is_preprint":false},{"year":2004,"finding":"Yeast MrpL36p (ortholog of human MRPL36) is an essential mitochondrial ribosomal large-subunit component. Its central L31-homologous domain is sufficient for general mitochondrial translation and co-sediments with the large ribosomal subunit. A novel N-terminal sequence and C-terminal Ffh-like domain are required for dosage suppression of COX2 mRNA translation defects but do not sediment with the large subunit, suggesting a separate mRNA-selection function.","method":"Sucrose gradient sedimentation, deletion/domain-swap genetics, dosage suppression assays in S. cerevisiae","journal":"Genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple genetic and biochemical approaches in one study, single lab","pmids":["15166137"],"is_preprint":false},{"year":2009,"finding":"Yeast Mrpl36 is associated with the mitochondrial ribosome large subunit and its mitochondria-specific C-terminal domain is not required for protein synthesis per se but is required for stability of Mrpl36 and for proper assembly of newly synthesized translation products into respiratory chain complexes; its absence leads to rapid degradation of translation products. Overexpression of Mrpl36 increases efficiency of mitochondrial translation. Mrpl36 stabilizes the interaction between large and small ribosomal subunits.","method":"Genetic deletion and domain truncation in yeast, pulse-chase analysis, sucrose gradient sedimentation, functional respiratory chain assembly assays","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (genetics, biochemical fractionation, pulse-chase), clear mechanistic phenotypes","pmids":["19339279"],"is_preprint":false},{"year":2017,"finding":"Yeast MrpL36 (bL31) assembles into a subcomplex with MrpL35 (mL38), MrpL7 (uL5), Mrp7 (bL27), MrpL17 (mL46), and MrpL28 (mL40) within the mitoribosomal central protuberance.","method":"Co-immunoprecipitation/co-purification of mitoribosomal subcomplex; yeast genetics","journal":"Molecular biology of the cell","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — biochemical subcomplex isolation, single lab, single study","pmids":["28931599"],"is_preprint":false},{"year":2020,"finding":"In GTPBP5-knockout human mitochondria, the mitoribosome large subunit (mtLSU) lacks bL36m (MRPL36), indicating that GTPBP5 function is required upstream of bL36m incorporation into the mtLSU during biogenesis.","method":"TALEN-induced KO cell line, sucrose gradient sedimentation, mass spectrometry of mtLSU particles","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean KO with defined assembly phenotype, single lab","pmids":["32652011"],"is_preprint":false},{"year":2022,"finding":"In human mitochondria, when MRM2 is absent, the mtLSU shows partial occupancy of bL36m (MRPL36) and the MALSU1:L0R8F8:mtACP anti-association module is bound. Cryo-EM structures at 2.6 Å resolution of these intermediates placed bL36m incorporation at a late-stage assembly checkpoint of the mtLSU.","method":"Cryo-EM structural analysis of assembly intermediates from MRM2-knockout cells; genome-wide transcriptome analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 / Moderate — cryo-EM structure with functional validation in KO cells, single lab but high-resolution structural data with multiple intermediates","pmids":["35177605"],"is_preprint":false},{"year":2024,"finding":"In S. cerevisiae, the zinc finger C2-CH motif of bL36m (MRPL36 ortholog) is essential for protein stability and mitoribosome assembly. Mutations in any of the four zinc-coordinating residues (C66, C69, C82, H88) reduce protein stability; C66 and C69 mutations have the most pronounced effect. Protein stability directly correlates with mitoribosome assembly competence and respiratory growth. Absence or mutation of bL36m leads to defective assembly of the L7/L12 stalk base of the large subunit.","method":"Site-directed mutagenesis of zinc-coordinating residues, mass spectrometry of large subunit particles, in vitro zinc-binding assay with synthetic proteins, yeast growth assays","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"High","confidence_rationale":"Tier 1 / Strong — reconstitution with mutagenesis, MS structural analysis, and functional assays in single rigorous study","pmids":["38493895"],"is_preprint":false},{"year":2025,"finding":"In S. cerevisiae, bL36m (MRPL36 ortholog) incorporation into the mitoribosome large subunit occurs during late mtLSU maturation, downstream of Mrh4-mediated bL33m incorporation, Mtg1-mediated rRNA refolding, and uL16m incorporation. Cryo-EM structures of assembly intermediates show that bL36m is incorporated together with uL6m, uL16m, and bL35m after Mtg1 restructures 21S rRNA helices H73–75 and H93.","method":"Cryo-EM of assembly intermediates, in vitro reconstitution, genetic epistasis, biochemical fractionation","journal":"Biochimica et biophysica acta. Molecular cell research","confidence":"High","confidence_rationale":"Tier 1 / Strong — cryo-EM structures combined with in vitro reconstitution and genetic epistasis in single study","pmids":["40865570"],"is_preprint":false},{"year":2026,"finding":"In S. cerevisiae, deletion of bL36m (RTC6/MRPL36 ortholog) selectively impairs synthesis of cytochrome c oxidase subunits encoded in the mitochondrial genome, reducing COX activity and growth on non-fermentable carbon sources, without causing global structural abnormalities of mitoribosomes or reducing their mRNA-binding ability. In contrast, in human cells, absence of bL36m does not substantially impact mitochondrial protein synthesis or ribosome assembly, though mitochondrial respiration is reduced.","method":"Gene deletion in yeast and human cells, pulse-chase mitochondrial translation assays, respiratory complex activity measurements, mitoribosome structural analysis","journal":"Biochemistry. Biokhimiia","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods in yeast and human cells, single lab, identifies functional divergence","pmids":["41702737"],"is_preprint":false}],"current_model":"MRPL36 (bL36m) is a zinc finger-containing protein of the mitochondrial ribosome large subunit that is incorporated at a late assembly checkpoint downstream of rRNA methylation and GTPase-mediated folding events; its zinc-binding C2-CH motif is essential for protein stability and proper assembly of the L7/L12 stalk base, and in yeast it plays a critical role in coordinating mitochondrial translation with respiratory chain complex assembly—particularly cytochrome c oxidase—through stabilization of large-small subunit interactions and generation of assembly-competent translation products, while also physically associating with the inner membrane protein LETM1 to regulate mitochondrial biogenesis and ATP production."},"narrative":{"mechanistic_narrative":"MRPL36 (bL36m) is a structural protein of the mitochondrial ribosome large subunit (mtLSU) that is incorporated at a late stage of mtLSU maturation and couples ribosome assembly to mitochondrial protein synthesis [PMID:19339279, PMID:35177605, PMID:40865570]. In yeast it associates with the large subunit and stabilizes the interaction between large and small ribosomal subunits; its mitochondria-specific C-terminal domain is dispensable for protein synthesis per se but required for bL36m stability and for assembly of newly made translation products into respiratory chain complexes, with its loss causing rapid degradation of these products [PMID:19339279]. Protein stability is governed by a C2-CH zinc finger motif (C66, C69, C82, H88), and disruption of zinc coordination destabilizes the protein and impairs assembly of the L7/L12 stalk base of the large subunit [PMID:38493895]. Cryo-EM of assembly intermediates places bL36m incorporation downstream of GTPase- and methyltransferase-dependent rRNA folding events, occurring together with uL6m, uL16m and bL35m after Mtg1 restructures 21S rRNA helices and downstream of GTPBP5 and MRM2 activity [PMID:32652011, PMID:35177605, PMID:40865570]. Functionally, yeast bL36m deletion selectively impairs synthesis of mitochondrially encoded cytochrome c oxidase subunits and reduces respiratory growth, whereas in human cells its absence reduces respiration without substantial effects on translation or assembly, indicating species-divergent roles [PMID:41702737]. MRPL36 also physically associates with the inner membrane protein LETM1, linking it to regulation of mitochondrial biogenesis and ATP production [PMID:19318571].","teleology":[{"year":2004,"claim":"Established that yeast MrpL36 is an essential large-subunit ribosomal component with separable domains, distinguishing a core translation function from an mRNA-selective activity for COX2.","evidence":"Sucrose gradient sedimentation, deletion/domain-swap genetics, and dosage suppression assays in S. cerevisiae","pmids":["15166137"],"confidence":"Medium","gaps":["Mechanism of mRNA selection by the N-terminal/Ffh-like domains not defined","Did not resolve where in assembly the protein is incorporated"]},{"year":2009,"claim":"Defined the functional role of the C-terminal domain in coupling translation to respiratory chain assembly and in stabilizing inter-subunit interactions.","evidence":"Genetic deletion/truncation, pulse-chase, sucrose gradient sedimentation, and respiratory complex assembly assays in yeast","pmids":["19339279"],"confidence":"High","gaps":["Structural basis for inter-subunit stabilization not shown","Mechanism linking translation product to degradation unclear"]},{"year":2009,"claim":"Linked MRPL36 to mitochondrial biogenesis regulation through physical association with the inner membrane protein LETM1.","evidence":"Reciprocal Co-immunoprecipitation and adenoviral overexpression with mitochondrial mass and ATP readouts","pmids":["19318571"],"confidence":"Medium","gaps":["Functional link rests on overexpression only","Interaction not confirmed beyond a single lab","Mechanism by which LETM1 binding affects ribosome function unknown"]},{"year":2017,"claim":"Placed MrpL36 within a defined central-protuberance subcomplex, providing structural context for its position in the mitoribosome.","evidence":"Co-immunoprecipitation/co-purification of a mitoribosomal subcomplex with yeast genetics","pmids":["28931599"],"confidence":"Medium","gaps":["Single biochemical isolation without structural confirmation","Order of subcomplex assembly not addressed"]},{"year":2020,"claim":"Positioned bL36m incorporation downstream of the assembly GTPase GTPBP5 in human mtLSU biogenesis.","evidence":"TALEN KO cell line, sucrose gradient sedimentation, and mass spectrometry of mtLSU particles","pmids":["32652011"],"confidence":"Medium","gaps":["Direct interaction with GTPBP5 not shown","Whether GTPBP5 acts directly on bL36m loading unresolved"]},{"year":2022,"claim":"Resolved bL36m incorporation as a late-stage mtLSU assembly checkpoint coordinated with the MALSU1 anti-association module.","evidence":"Cryo-EM of assembly intermediates from MRM2-KO human cells with transcriptome analysis","pmids":["35177605"],"confidence":"High","gaps":["Trigger for bL36m loading not defined","Relationship between rRNA methylation status and bL36m occupancy mechanistically open"]},{"year":2024,"claim":"Identified the C2-CH zinc finger as the determinant of bL36m stability and showed stability dictates assembly competence and stalk-base formation.","evidence":"Site-directed mutagenesis of zinc-coordinating residues, MS of large-subunit particles, in vitro zinc-binding assays, and yeast growth assays","pmids":["38493895"],"confidence":"High","gaps":["Structural mechanism by which zinc binding promotes L7/L12 stalk-base assembly not directly visualized","In vivo zinc loading dynamics unaddressed"]},{"year":2025,"claim":"Ordered bL36m incorporation within the late mtLSU maturation pathway relative to other proteins and Mtg1-mediated rRNA refolding.","evidence":"Cryo-EM of assembly intermediates, in vitro reconstitution, genetic epistasis, and biochemical fractionation in yeast","pmids":["40865570"],"confidence":"High","gaps":["Whether co-incorporated proteins are interdependent not fully dissected","Conservation of this exact order in humans not established here"]},{"year":2026,"claim":"Revealed species divergence: yeast bL36m selectively supports cytochrome c oxidase subunit synthesis, while human bL36m loss affects respiration without major translation/assembly defects.","evidence":"Gene deletion in yeast and human cells, pulse-chase translation assays, respiratory complex activity, and mitoribosome structural analysis","pmids":["41702737"],"confidence":"Medium","gaps":["Molecular basis for COX-selective effect in yeast unknown","Mechanism of reduced human respiration despite intact translation undefined"]},{"year":null,"claim":"How the LETM1 association and the ribosomal assembly role of MRPL36 are mechanistically connected, and how human bL36m influences respiration without affecting translation, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of the human MRPL36-LETM1 interaction","Downstream effector linking bL36m loss to respiratory decline in human cells not identified"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[1,2,6]}],"localization":[{"term_id":"GO:0005840","term_label":"ribosome","supporting_discovery_ids":[1,2,3,5,7]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[0,2,8]}],"pathway":[{"term_id":"R-HSA-8953854","term_label":"Metabolism of RNA","supporting_discovery_ids":[2,5,7]},{"term_id":"R-HSA-1852241","term_label":"Organelle biogenesis and maintenance","supporting_discovery_ids":[4,5,7]}],"complexes":["mitochondrial ribosome large subunit (mtLSU)","mitoribosomal central protuberance subcomplex","LETM1-MRPL36 complex"],"partners":["LETM1","MRPL35","MRPL7","MRP7","MRPL17","MRPL28"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q9P0J6","full_name":"Large ribosomal subunit protein bL36m","aliases":["39S ribosomal protein L36, mitochondrial","L36mt","MRP-L36","BRCA1-interacting protein 1"],"length_aa":103,"mass_kda":11.8,"function":"","subcellular_location":"Mitochondrion","url":"https://www.uniprot.org/uniprotkb/Q9P0J6/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":true,"resolved_as":"","url":"https://depmap.org/portal/gene/MRPL36","classification":"Common Essential","n_dependent_lines":773,"n_total_lines":1208,"dependency_fraction":0.6399006622516556},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/MRPL36","total_profiled":1310},"omim":[{"mim_id":"611842","title":"MITOCHONDRIAL RIBOSOMAL PROTEIN L36; MRPL36","url":"https://www.omim.org/entry/611842"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Mitochondria","reliability":"Supported"},{"location":"Nuclear bodies","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MRPL36"},"hgnc":{"alias_symbol":["RPMJ","L36mt","PRPL36","MRP-L36","bL36m"],"prev_symbol":[]},"alphafold":{"accession":"Q9P0J6","domains":[{"cath_id":"-","chopping":"66-101","consensus_level":"high","plddt":96.9589,"start":66,"end":101}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P0J6","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P0J6-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P0J6-F1-predicted_aligned_error_v6.png","plddt_mean":71.5},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MRPL36","jax_strain_url":"https://www.jax.org/strain/search?query=MRPL36"},"sequence":{"accession":"Q9P0J6","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9P0J6.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9P0J6/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P0J6"}},"corpus_meta":[{"pmid":"19318571","id":"PMC_19318571","title":"Association of LETM1 and MRPL36 contributes to the regulation of mitochondrial ATP production and necrotic cell death.","date":"2009","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/19318571","citation_count":66,"is_preprint":false},{"pmid":"3298224","id":"PMC_3298224","title":"Primary structures of and genes for new ribosomal proteins A and B in Escherichia coli.","date":"1987","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/3298224","citation_count":65,"is_preprint":false},{"pmid":"16735738","id":"PMC_16735738","title":"Promoter prediction in the rhizobia.","date":"2006","source":"Microbiology (Reading, England)","url":"https://pubmed.ncbi.nlm.nih.gov/16735738","citation_count":63,"is_preprint":false},{"pmid":"26261349","id":"PMC_26261349","title":"Single methylation of 23S rRNA triggers late steps of 50S ribosomal subunit assembly.","date":"2015","source":"Proceedings of the National Academy of Sciences of the United States of 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LETM1 acts as an anchor protein for this interaction. LETM1 overexpression reduces mitochondrial biogenesis and ATP production, and this regulation involves the LETM1-MRPL36 complex.\",\n      \"method\": \"Co-immunoprecipitation; adenovirus-mediated overexpression with functional readouts (mitochondrial mass, ATP production)\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — reciprocal Co-IP shown but single lab, single study; functional link established by overexpression only\",\n      \"pmids\": [\"19318571\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Yeast MrpL36p (ortholog of human MRPL36) is an essential mitochondrial ribosomal large-subunit component. Its central L31-homologous domain is sufficient for general mitochondrial translation and co-sediments with the large ribosomal subunit. A novel N-terminal sequence and C-terminal Ffh-like domain are required for dosage suppression of COX2 mRNA translation defects but do not sediment with the large subunit, suggesting a separate mRNA-selection function.\",\n      \"method\": \"Sucrose gradient sedimentation, deletion/domain-swap genetics, dosage suppression assays in S. cerevisiae\",\n      \"journal\": \"Genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple genetic and biochemical approaches in one study, single lab\",\n      \"pmids\": [\"15166137\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"Yeast Mrpl36 is associated with the mitochondrial ribosome large subunit and its mitochondria-specific C-terminal domain is not required for protein synthesis per se but is required for stability of Mrpl36 and for proper assembly of newly synthesized translation products into respiratory chain complexes; its absence leads to rapid degradation of translation products. Overexpression of Mrpl36 increases efficiency of mitochondrial translation. Mrpl36 stabilizes the interaction between large and small ribosomal subunits.\",\n      \"method\": \"Genetic deletion and domain truncation in yeast, pulse-chase analysis, sucrose gradient sedimentation, functional respiratory chain assembly assays\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (genetics, biochemical fractionation, pulse-chase), clear mechanistic phenotypes\",\n      \"pmids\": [\"19339279\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Yeast MrpL36 (bL31) assembles into a subcomplex with MrpL35 (mL38), MrpL7 (uL5), Mrp7 (bL27), MrpL17 (mL46), and MrpL28 (mL40) within the mitoribosomal central protuberance.\",\n      \"method\": \"Co-immunoprecipitation/co-purification of mitoribosomal subcomplex; yeast genetics\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — biochemical subcomplex isolation, single lab, single study\",\n      \"pmids\": [\"28931599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In GTPBP5-knockout human mitochondria, the mitoribosome large subunit (mtLSU) lacks bL36m (MRPL36), indicating that GTPBP5 function is required upstream of bL36m incorporation into the mtLSU during biogenesis.\",\n      \"method\": \"TALEN-induced KO cell line, sucrose gradient sedimentation, mass spectrometry of mtLSU particles\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean KO with defined assembly phenotype, single lab\",\n      \"pmids\": [\"32652011\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In human mitochondria, when MRM2 is absent, the mtLSU shows partial occupancy of bL36m (MRPL36) and the MALSU1:L0R8F8:mtACP anti-association module is bound. Cryo-EM structures at 2.6 Å resolution of these intermediates placed bL36m incorporation at a late-stage assembly checkpoint of the mtLSU.\",\n      \"method\": \"Cryo-EM structural analysis of assembly intermediates from MRM2-knockout cells; genome-wide transcriptome analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — cryo-EM structure with functional validation in KO cells, single lab but high-resolution structural data with multiple intermediates\",\n      \"pmids\": [\"35177605\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In S. cerevisiae, the zinc finger C2-CH motif of bL36m (MRPL36 ortholog) is essential for protein stability and mitoribosome assembly. Mutations in any of the four zinc-coordinating residues (C66, C69, C82, H88) reduce protein stability; C66 and C69 mutations have the most pronounced effect. Protein stability directly correlates with mitoribosome assembly competence and respiratory growth. Absence or mutation of bL36m leads to defective assembly of the L7/L12 stalk base of the large subunit.\",\n      \"method\": \"Site-directed mutagenesis of zinc-coordinating residues, mass spectrometry of large subunit particles, in vitro zinc-binding assay with synthetic proteins, yeast growth assays\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — reconstitution with mutagenesis, MS structural analysis, and functional assays in single rigorous study\",\n      \"pmids\": [\"38493895\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In S. cerevisiae, bL36m (MRPL36 ortholog) incorporation into the mitoribosome large subunit occurs during late mtLSU maturation, downstream of Mrh4-mediated bL33m incorporation, Mtg1-mediated rRNA refolding, and uL16m incorporation. Cryo-EM structures of assembly intermediates show that bL36m is incorporated together with uL6m, uL16m, and bL35m after Mtg1 restructures 21S rRNA helices H73–75 and H93.\",\n      \"method\": \"Cryo-EM of assembly intermediates, in vitro reconstitution, genetic epistasis, biochemical fractionation\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular cell research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — cryo-EM structures combined with in vitro reconstitution and genetic epistasis in single study\",\n      \"pmids\": [\"40865570\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In S. cerevisiae, deletion of bL36m (RTC6/MRPL36 ortholog) selectively impairs synthesis of cytochrome c oxidase subunits encoded in the mitochondrial genome, reducing COX activity and growth on non-fermentable carbon sources, without causing global structural abnormalities of mitoribosomes or reducing their mRNA-binding ability. In contrast, in human cells, absence of bL36m does not substantially impact mitochondrial protein synthesis or ribosome assembly, though mitochondrial respiration is reduced.\",\n      \"method\": \"Gene deletion in yeast and human cells, pulse-chase mitochondrial translation assays, respiratory complex activity measurements, mitoribosome structural analysis\",\n      \"journal\": \"Biochemistry. Biokhimiia\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods in yeast and human cells, single lab, identifies functional divergence\",\n      \"pmids\": [\"41702737\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MRPL36 (bL36m) is a zinc finger-containing protein of the mitochondrial ribosome large subunit that is incorporated at a late assembly checkpoint downstream of rRNA methylation and GTPase-mediated folding events; its zinc-binding C2-CH motif is essential for protein stability and proper assembly of the L7/L12 stalk base, and in yeast it plays a critical role in coordinating mitochondrial translation with respiratory chain complex assembly—particularly cytochrome c oxidase—through stabilization of large-small subunit interactions and generation of assembly-competent translation products, while also physically associating with the inner membrane protein LETM1 to regulate mitochondrial biogenesis and ATP production.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MRPL36 (bL36m) is a structural protein of the mitochondrial ribosome large subunit (mtLSU) that is incorporated at a late stage of mtLSU maturation and couples ribosome assembly to mitochondrial protein synthesis [#2, #5, #7]. In yeast it associates with the large subunit and stabilizes the interaction between large and small ribosomal subunits; its mitochondria-specific C-terminal domain is dispensable for protein synthesis per se but required for bL36m stability and for assembly of newly made translation products into respiratory chain complexes, with its loss causing rapid degradation of these products [#2]. Protein stability is governed by a C2-CH zinc finger motif (C66, C69, C82, H88), and disruption of zinc coordination destabilizes the protein and impairs assembly of the L7/L12 stalk base of the large subunit [#6]. Cryo-EM of assembly intermediates places bL36m incorporation downstream of GTPase- and methyltransferase-dependent rRNA folding events, occurring together with uL6m, uL16m and bL35m after Mtg1 restructures 21S rRNA helices and downstream of GTPBP5 and MRM2 activity [#4, #5, #7]. Functionally, yeast bL36m deletion selectively impairs synthesis of mitochondrially encoded cytochrome c oxidase subunits and reduces respiratory growth, whereas in human cells its absence reduces respiration without substantial effects on translation or assembly, indicating species-divergent roles [#8]. MRPL36 also physically associates with the inner membrane protein LETM1, linking it to regulation of mitochondrial biogenesis and ATP production [#0].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established that yeast MrpL36 is an essential large-subunit ribosomal component with separable domains, distinguishing a core translation function from an mRNA-selective activity for COX2.\",\n      \"evidence\": \"Sucrose gradient sedimentation, deletion/domain-swap genetics, and dosage suppression assays in S. cerevisiae\",\n      \"pmids\": [\"15166137\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of mRNA selection by the N-terminal/Ffh-like domains not defined\", \"Did not resolve where in assembly the protein is incorporated\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined the functional role of the C-terminal domain in coupling translation to respiratory chain assembly and in stabilizing inter-subunit interactions.\",\n      \"evidence\": \"Genetic deletion/truncation, pulse-chase, sucrose gradient sedimentation, and respiratory complex assembly assays in yeast\",\n      \"pmids\": [\"19339279\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for inter-subunit stabilization not shown\", \"Mechanism linking translation product to degradation unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Linked MRPL36 to mitochondrial biogenesis regulation through physical association with the inner membrane protein LETM1.\",\n      \"evidence\": \"Reciprocal Co-immunoprecipitation and adenoviral overexpression with mitochondrial mass and ATP readouts\",\n      \"pmids\": [\"19318571\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Functional link rests on overexpression only\", \"Interaction not confirmed beyond a single lab\", \"Mechanism by which LETM1 binding affects ribosome function unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Placed MrpL36 within a defined central-protuberance subcomplex, providing structural context for its position in the mitoribosome.\",\n      \"evidence\": \"Co-immunoprecipitation/co-purification of a mitoribosomal subcomplex with yeast genetics\",\n      \"pmids\": [\"28931599\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single biochemical isolation without structural confirmation\", \"Order of subcomplex assembly not addressed\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Positioned bL36m incorporation downstream of the assembly GTPase GTPBP5 in human mtLSU biogenesis.\",\n      \"evidence\": \"TALEN KO cell line, sucrose gradient sedimentation, and mass spectrometry of mtLSU particles\",\n      \"pmids\": [\"32652011\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct interaction with GTPBP5 not shown\", \"Whether GTPBP5 acts directly on bL36m loading unresolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved bL36m incorporation as a late-stage mtLSU assembly checkpoint coordinated with the MALSU1 anti-association module.\",\n      \"evidence\": \"Cryo-EM of assembly intermediates from MRM2-KO human cells with transcriptome analysis\",\n      \"pmids\": [\"35177605\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trigger for bL36m loading not defined\", \"Relationship between rRNA methylation status and bL36m occupancy mechanistically open\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identified the C2-CH zinc finger as the determinant of bL36m stability and showed stability dictates assembly competence and stalk-base formation.\",\n      \"evidence\": \"Site-directed mutagenesis of zinc-coordinating residues, MS of large-subunit particles, in vitro zinc-binding assays, and yeast growth assays\",\n      \"pmids\": [\"38493895\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural mechanism by which zinc binding promotes L7/L12 stalk-base assembly not directly visualized\", \"In vivo zinc loading dynamics unaddressed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Ordered bL36m incorporation within the late mtLSU maturation pathway relative to other proteins and Mtg1-mediated rRNA refolding.\",\n      \"evidence\": \"Cryo-EM of assembly intermediates, in vitro reconstitution, genetic epistasis, and biochemical fractionation in yeast\",\n      \"pmids\": [\"40865570\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether co-incorporated proteins are interdependent not fully dissected\", \"Conservation of this exact order in humans not established here\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Revealed species divergence: yeast bL36m selectively supports cytochrome c oxidase subunit synthesis, while human bL36m loss affects respiration without major translation/assembly defects.\",\n      \"evidence\": \"Gene deletion in yeast and human cells, pulse-chase translation assays, respiratory complex activity, and mitoribosome structural analysis\",\n      \"pmids\": [\"41702737\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis for COX-selective effect in yeast unknown\", \"Mechanism of reduced human respiration despite intact translation undefined\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the LETM1 association and the ribosomal assembly role of MRPL36 are mechanistically connected, and how human bL36m influences respiration without affecting translation, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of the human MRPL36-LETM1 interaction\", \"Downstream effector linking bL36m loss to respiratory decline in human cells not identified\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [1, 2, 6]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005840\", \"supporting_discovery_ids\": [1, 2, 3, 5, 7]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [0, 2, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-8953854\", \"supporting_discovery_ids\": [2, 5, 7]},\n      {\"term_id\": \"R-HSA-1852241\", \"supporting_discovery_ids\": [4, 5, 7]}\n    ],\n    \"complexes\": [\n      \"mitochondrial ribosome large subunit (mtLSU)\",\n      \"mitoribosomal central protuberance subcomplex\",\n      \"LETM1-MRPL36 complex\"\n    ],\n    \"partners\": [\n      \"LETM1\",\n      \"MRPL35\",\n      \"MRPL7\",\n      \"MRP7\",\n      \"MRPL17\",\n      \"MRPL28\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":6,"faith_total":6,"faith_pct":100.0}}