MTO1 (mitochondrial tRNA translation optimization 1) is the human homolog of bacterial MnmG/GidA and yeast Mto1, an FAD-dependent enzyme of the MnmG family encoded in the nucleus and imported into mitochondria. With the GTPase GTPBP3 (the MnmE homolog) it forms the GTPBP3-MTO1 complex, which installs 5-taurinomethyluridine (taum5U) at the wobble position U34 of five mitochondrial tRNAs (Leu(UUR), Trp, Lys, Glu and Gln), using 5,10-methylene-tetrahydrofolate and taurine as substrates and GTP, FAD and potassium as cofactors. The modification supports accurate and efficient decoding during mitochondrial translation; loss of MTO1 abolishes taum5U34 and reduces mtDNA-dependent respiratory chain activities. Biallelic MTO1 variants cause combined oxidative phosphorylation deficiency 10 (COXPD10), typically infantile hypertrophic cardiomyopathy with lactic acidosis. Human MTO1 complements the respiratory defect of yeast mto1 mutants.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003723 RNA binding | HDA PMID:22681889 The mRNA-bound proteome and its global occupancy profile on ... | KEEP AS NON CORE | Summary: Generic RNA binding from mRNA interactome capture in HEK293 cells, which recovered MTO1 among ~800 poly(A) RNA-associated proteins. Reason: The high-throughput capture shows that MTO1 associates with RNA, which is consistent with an enzyme whose substrates are mitochondrial tRNAs. The capture does not say which RNA is bound, and mRNA binding is not part of MTO1's known function. No human tRNA-binding assay was found that would justify a more specific term, so the generic term is kept as non-core rather than replaced. Supporting Evidence: PMID:22681889 Application to a human embryonic kidney cell line identified close to 800 proteins. PMID:29390138 Here, we elucidated Οm5U biogenesis by confirming that 5,10-methylene-tetrahydrofolate and taurine are metabolic substrates for Οm5U formation catalyzed by MTO1 and GTPBP3. |
| GO:0005739 mitochondrion | HTP PMID:34800366 Quantitative high-confidence human mitochondrial proteome an... | ACCEPT | Summary: Mitochondrion (HTP). MTO1 is a nuclear-encoded precursor imported into mitochondria, where it modifies mt-tRNAs. Reason: Mitochondrial localization is consistent across the high-throughput mitochondrial proteome, UniProt (by similarity to mouse Q923Z3), the PANTHER family, and function: the substrates are mt-tRNAs and loss of MTO1 removes taum5U34 from mt-tRNAs. The matrix is the likely sub-compartment, but no direct sub-mitochondrial localization data for human MTO1 were found, so the general term is accepted. Supporting Evidence: file:human/MTO1/MTO1-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: Mitochondrion (IBA). MTO1 is a nuclear-encoded precursor imported into mitochondria, where it modifies mt-tRNAs. Reason: Mitochondrial localization is consistent across the high-throughput mitochondrial proteome, UniProt (by similarity to mouse Q923Z3), the PANTHER family, and function: the substrates are mt-tRNAs and loss of MTO1 removes taum5U34 from mt-tRNAs. The matrix is the likely sub-compartment, but no direct sub-mitochondrial localization data for human MTO1 were found, so the general term is accepted. Supporting Evidence: file:human/MTO1/MTO1-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. |
| GO:0005739 mitochondrion | IEA GO_REF:0000044 | ACCEPT | Summary: Mitochondrion (IEA). MTO1 is a nuclear-encoded precursor imported into mitochondria, where it modifies mt-tRNAs. Reason: Mitochondrial localization is consistent across the high-throughput mitochondrial proteome, UniProt (by similarity to mouse Q923Z3), the PANTHER family, and function: the substrates are mt-tRNAs and loss of MTO1 removes taum5U34 from mt-tRNAs. The matrix is the likely sub-compartment, but no direct sub-mitochondrial localization data for human MTO1 were found, so the general term is accepted. Supporting Evidence: file:human/MTO1/MTO1-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. |
| GO:0005739 mitochondrion | ISS GO_REF:0000024 | ACCEPT | Summary: Mitochondrion (ISS). MTO1 is a nuclear-encoded precursor imported into mitochondria, where it modifies mt-tRNAs. Reason: Mitochondrial localization is consistent across the high-throughput mitochondrial proteome, UniProt (by similarity to mouse Q923Z3), the PANTHER family, and function: the substrates are mt-tRNAs and loss of MTO1 removes taum5U34 from mt-tRNAs. The matrix is the likely sub-compartment, but no direct sub-mitochondrial localization data for human MTO1 were found, so the general term is accepted. Supporting Evidence: file:human/MTO1/MTO1-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. |
| GO:0008033 tRNA processing | IEA GO_REF:0000002 | TOO GENERAL | Summary: tRNA processing from InterPro2GO mapping of the MnmG-related family (IPR002218). Reason: True but uninformative. MTO1 modifies U34 of mt-tRNAs, which is a tRNA modification and so falls under tRNA processing, but GO:0070899 mitochondrial tRNA wobble uridine modification (an is_a descendant of GO:0008033) is accepted in this review from the IBA and IMP rows and already entails this term. Supporting Evidence: PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. |
| GO:0050660 flavin adenine dinucleotide binding | IEA GO_REF:0000002 | ACCEPT | Summary: FAD binding from InterPro2GO mapping of the MnmG-related family. Reason: MTO1 belongs to the MnmG family, whose members are FAD-dependent, and UniProt assigns FAD as the cofactor by similarity to Aquifex aeolicus MnmG. FAD is one of the cofactors in the in vitro reconstitution of taum5U34 by the GTPBP3-MTO1 complex. No direct FAD-binding assay on human MTO1 was found, but the inference is well founded on family and fold. Supporting Evidence: file:human/MTO1/MTO1-uniprot.txt Name=FAD; Xref=ChEBI:CHEBI:57692; file:human/MTO1/MTO1-uniprot.txt Belongs to the MnmG family. PMID:29390138 we conducted in vitro reconstitution of Οm5U34 on mt-tRNALeu(UUR) with the GTPBP3βMTO1-FLAG complex in the presence of taurine, 5,10-CH2-THF and co-factors including GTP, FAD and potassium ion. |
| GO:0070899 mitochondrial tRNA wobble uridine modification | IBA GO_REF:0000033 | ACCEPT | Summary: Mitochondrial tRNA wobble uridine modification (IBA). Reason: Core process, consistent with the experimental IMP annotation from Mto1 knockout cells and with the conserved MnmG-family role in U34 modification. The human gene appearing among the IBA sources reflects its own experimental annotation, which is expected. Supporting Evidence: PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. file:human/MTO1/MTO1-uniprot.txt Component of the GTPBP3-MTO1 complex that catalyzes the 5- taurinomethyluridine (taum(5)U) modification at the 34th wobble position (U34) of mitochondrial tRNAs (mt-tRNAs) |
| GO:0070899 mitochondrial tRNA wobble uridine modification | IEA GO_REF:0000117 | ACCEPT | Summary: Mitochondrial tRNA wobble uridine modification (IEA). Reason: Core process, consistent with the experimental IMP annotation from Mto1 knockout cells and with the conserved MnmG-family role in U34 modification. The human gene appearing among the IBA sources reflects its own experimental annotation, which is expected. Supporting Evidence: PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. file:human/MTO1/MTO1-uniprot.txt Component of the GTPBP3-MTO1 complex that catalyzes the 5- taurinomethyluridine (taum(5)U) modification at the 34th wobble position (U34) of mitochondrial tRNAs (mt-tRNAs) |
| GO:0070899 mitochondrial tRNA wobble uridine modification | IMP PMID:29390138 Metabolic and chemical regulation of tRNA modification assoc... | ACCEPT | Summary: Mitochondrial tRNA wobble uridine modification, supported by loss of taum5U34 from mt-tRNAs in Mto1 knockout mouse ES cells. Reason: Core process. Mto1 KO cells lack taum5(s2)U34 in mt-tRNAs, and the GTPBP3-MTO1 complex reconstitutes taum5U34 formation in vitro. MTO1 is a subunit of the modifying enzyme, so it performs the step rather than merely being required for it. Supporting Evidence: PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. PMID:29390138 Finally, we successfully reconstituted Οm5U34 formation in mt-tRNA in vitro in a system consisting of GTPBP3 and MTO1 in the presence of taurine, the methylene-THF, guanosine triphosphate (GTP) and other co-factors. |
| GO:0160236 tRNA 5-taurinomethyluridine synthase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Contributes to tRNA 5-taurinomethyluridine synthase activity (IBA), the activity of the GTPBP3-MTO1 complex. Reason: Core activity. The reaction (U34 + 5,10-methylene-THF + taurine + GTP to taum5U34) is catalysed by the GTPBP3-MTO1 complex, and taum5U34 is absent from mt-tRNAs in Mto1 knockout cells. MTO1 is the FAD-dependent MnmG-family subunit; GTPBP3 supplies the GTPase. Because the activity is defined for the complex, the contributes_to qualifier is appropriate. Supporting Evidence: PMID:29390138 Here, we elucidated Οm5U biogenesis by confirming that 5,10-methylene-tetrahydrofolate and taurine are metabolic substrates for Οm5U formation catalyzed by MTO1 and GTPBP3. PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. file:human/MTO1/MTO1-uniprot.txt Component of the GTPBP3-MTO1 complex that catalyzes the 5- taurinomethyluridine (taum(5)U) modification at the 34th wobble position (U34) of mitochondrial tRNAs (mt-tRNAs) |
| GO:0160236 tRNA 5-taurinomethyluridine synthase activity | IMP PMID:29390138 Metabolic and chemical regulation of tRNA modification assoc... | ACCEPT | Summary: Contributes to tRNA 5-taurinomethyluridine synthase activity (IMP), the activity of the GTPBP3-MTO1 complex. Reason: Core activity. The reaction (U34 + 5,10-methylene-THF + taurine + GTP to taum5U34) is catalysed by the GTPBP3-MTO1 complex, and taum5U34 is absent from mt-tRNAs in Mto1 knockout cells. MTO1 is the FAD-dependent MnmG-family subunit; GTPBP3 supplies the GTPase. Because the activity is defined for the complex, the contributes_to qualifier is appropriate. Supporting Evidence: PMID:29390138 Here, we elucidated Οm5U biogenesis by confirming that 5,10-methylene-tetrahydrofolate and taurine are metabolic substrates for Οm5U formation catalyzed by MTO1 and GTPBP3. PMID:29390138 We here clearly demonstrated that Οm5(s2)U34 was absent from mt-tRNAs isolated from GTPBP3 KO cells, Mto1 KO cells, as well as fibroblasts of a patient with pathogenic mutations in GTPBP3. file:human/MTO1/MTO1-uniprot.txt Component of the GTPBP3-MTO1 complex that catalyzes the 5- taurinomethyluridine (taum(5)U) modification at the 34th wobble position (U34) of mitochondrial tRNAs (mt-tRNAs) |
| GO:7770010 GTPBP3-MTO1 complex | IBA GO_REF:0000033 | ACCEPT | Summary: GTPBP3-MTO1 complex (IBA). Reason: MTO1 is one of the two subunits of the GTPBP3-MTO1 complex, which was purified from human cells and reconstitutes taum5U34 formation. The complex term is consistent with the IDA co-immunoprecipitation and the conserved MnmE-MnmG partnership. Supporting Evidence: PMID:29390138 Finally, we successfully reconstituted Οm5U34 formation in mt-tRNA in vitro in a system consisting of GTPBP3 and MTO1 in the presence of taurine, the methylene-THF, guanosine triphosphate (GTP) and other co-factors. PMID:33619562 Using an anti-hGTPBP3 antibody in Co-IP, we confirmed that endogenous hMTO1 was indeed coprecipitated (Figure 1E). |
| GO:7770010 GTPBP3-MTO1 complex | IDA PMID:33619562 The human tRNA taurine modification enzyme GTPBP3 is an acti... | ACCEPT | Summary: GTPBP3-MTO1 complex, from co-immunoprecipitation of endogenous MTO1 with endogenous GTPBP3 in human cells. Reason: Endogenous MTO1 co-precipitates with endogenous GTPBP3, and the tagged complex can be purified from HEK293T cells and is active in vitro. This is direct evidence that MTO1 is a component of the complex. Supporting Evidence: PMID:33619562 Using an anti-hGTPBP3 antibody in Co-IP, we confirmed that endogenous hMTO1 was indeed coprecipitated (Figure 1E). PMID:29390138 we conducted in vitro reconstitution of Οm5U34 on mt-tRNALeu(UUR) with the GTPBP3βMTO1-FLAG complex in the presence of taurine, 5,10-CH2-THF and co-factors including GTP, FAD and potassium ion. |
| GO:7770010 GTPBP3-MTO1 complex | IMP PMID:29390138 Metabolic and chemical regulation of tRNA modification assoc... | ACCEPT | Summary: GTPBP3-MTO1 complex (IMP). Reason: MTO1 is one of the two subunits of the GTPBP3-MTO1 complex, which was purified from human cells and reconstitutes taum5U34 formation. The complex term is consistent with the IDA co-immunoprecipitation and the conserved MnmE-MnmG partnership. Supporting Evidence: PMID:29390138 Finally, we successfully reconstituted Οm5U34 formation in mt-tRNA in vitro in a system consisting of GTPBP3 and MTO1 in the presence of taurine, the methylene-THF, guanosine triphosphate (GTP) and other co-factors. PMID:33619562 Using an anti-hGTPBP3 antibody in Co-IP, we confirmed that endogenous hMTO1 was indeed coprecipitated (Figure 1E). |
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Download this section (compressed HTML)Q: Within the GTPBP3-MTO1 complex, does MTO1 alone carry out the FAD-dependent transfer of the methylene group from 5,10-methylene-THF to U34 and the taurine addition, as inferred from bacterial MnmG, or do both subunits contribute catalytic residues?
Q: Why do MTO1 variants present mainly with hypertrophic cardiomyopathy while GTPBP3 variants more often add encephalopathy, given that both abolish the same modification?
Experiment: Reconstitute taum5U34 formation with purified human MTO1 carrying mutations in the FAD-binding site or in residues equivalent to MnmG catalytic cysteines, combined with wild-type GTPBP3, and measure product by LC-MS.
Experiment: Measure FAD binding and redox state of purified human MTO1 and the effect of COXPD10 missense variants (for example p.Ala428Thr) on FAD binding, complex formation with GTPBP3 and tRNA binding.
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