GatB (CG5463) encodes the B subunit of the mitochondrial glutamyl-tRNA(Gln) amidotransferase (GatCAB). Because mitochondria lack a glutaminyl-tRNA synthetase, tRNA(Gln) is charged with glutamate, and GatCAB converts the misacylated Glu-tRNA(Gln) into Gln-tRNA(Gln). GatB binds the tRNA, uses ATP to phosphorylate the glutamate side chain and amidates the activated intermediate with ammonia channelled from the glutaminase subunit GatA. The complex supplies Gln-tRNA(Gln) for mitochondrial translation. Function is inferred from orthologs and from the conserved GatB domain; GatB has not been studied directly in flies.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | MODIFY | Summary: Generic catalytic activity (InterPro). Reason: Uninformative; GatB carries the kinase and amidotransferase half-reactions of glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity. The replacement term is already annotated (below), so this records the preferred term rather than a new assertion. Proposed replacements: glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity Supporting Evidence: file:DROME/GatB/GatB-uniprot.txt This subunit probably recognizes tRNA(Gln) |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: Mitochondrion. Reason: GatCAB transamidates mitochondrial Glu-tRNA(Gln); all three fly subunits belong to the mitochondrial Gat subfamilies. Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
| GO:0005739 mitochondrion | IEA GO_REF:0000120 | ACCEPT | Summary: Mitochondrion. Reason: GatCAB transamidates mitochondrial Glu-tRNA(Gln); all three fly subunits belong to the mitochondrial Gat subfamilies. Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
| GO:0005739 mitochondrion | ISS GO_REF:0000024 | ACCEPT | Summary: Mitochondrion. Reason: GatCAB transamidates mitochondrial Glu-tRNA(Gln); all three fly subunits belong to the mitochondrial Gat subfamilies. Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
| GO:0016874 ligase activity | IEA GO_REF:0000002 | MODIFY | Summary: Ligase activity (InterPro). Reason: Correct but a very general parent; MODIFY to glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity, which GatB already carries (IBA, IEA, ISS). Proposed replacements: glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity |
| GO:0016884 carbon-nitrogen ligase activity, with glutamine as amido-N-donor | IEA GO_REF:0000120 | MODIFY | Summary: Carbon-nitrogen ligase activity, with glutamine as amido-N-donor. Reason: Correct parent of the specific transamidase activity; MODIFY to glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity, which GatB already carries (IBA, IEA, ISS). Proposed replacements: glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity |
| GO:0030956 glutamyl-tRNA(Gln) amidotransferase complex | IBA GO_REF:0000033 | ACCEPT | Summary: Subunit of the glutamyl-tRNA(Gln) amidotransferase (GatCAB) complex. Reason: Flies encode single GatA, GatB and GatC orthologs, which together form the heterotrimeric mitochondrial amidotransferase. Supporting Evidence: PMID:26761199 CG5463 and CG33649 genes – we propose to name the latter two GatB and GatC, respectively |
| GO:0030956 glutamyl-tRNA(Gln) amidotransferase complex | IEA GO_REF:0000104 | ACCEPT | Summary: Subunit of the glutamyl-tRNA(Gln) amidotransferase (GatCAB) complex. Reason: Flies encode single GatA, GatB and GatC orthologs, which together form the heterotrimeric mitochondrial amidotransferase. Supporting Evidence: PMID:26761199 CG5463 and CG33649 genes – we propose to name the latter two GatB and GatC, respectively |
| GO:0030956 glutamyl-tRNA(Gln) amidotransferase complex | ISS GO_REF:0000024 | ACCEPT | Summary: Subunit of the glutamyl-tRNA(Gln) amidotransferase (GatCAB) complex. Reason: Flies encode single GatA, GatB and GatC orthologs, which together form the heterotrimeric mitochondrial amidotransferase. Supporting Evidence: PMID:26761199 CG5463 and CG33649 genes – we propose to name the latter two GatB and GatC, respectively |
| GO:0032543 mitochondrial translation | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Mitochondrial translation. Reason: GatCAB supplies Gln-tRNA(Gln) for mitochondrial protein synthesis (there is no mitochondrial GlnRS), so the involvement is real, but the specific step is captured better by conversion of glutamyl-tRNA to glutaminyl-tRNA. Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
| GO:0032543 mitochondrial translation | IEA GO_REF:0000104 | KEEP AS NON CORE | Summary: Mitochondrial translation. Reason: GatCAB supplies Gln-tRNA(Gln) for mitochondrial protein synthesis (there is no mitochondrial GlnRS), so the involvement is real, but the specific step is captured better by conversion of glutamyl-tRNA to glutaminyl-tRNA. Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
| GO:0032543 mitochondrial translation | ISS GO_REF:0000024 | KEEP AS NON CORE | Summary: Mitochondrial translation. Reason: GatCAB supplies Gln-tRNA(Gln) for mitochondrial protein synthesis (there is no mitochondrial GlnRS), so the involvement is real, but the specific step is captured better by conversion of glutamyl-tRNA to glutaminyl-tRNA. Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
| GO:0050567 glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity | IBA GO_REF:0000033 | ACCEPT | Summary: Contributes to glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity. Reason: Core function; transamidation needs GatB together with GatA (ammonia) and GatC. Supporting Evidence: file:DROME/GatB/GatB-uniprot.txt This subunit probably recognizes tRNA(Gln) file:DROME/GatB/GatB-deep-research-falcon.md depletion of GatCAB accumulated Glu–tRNA^Gln while mitochondrial tRNA^Glu remained aminoacylated |
| GO:0050567 glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity | IEA GO_REF:0000120 | ACCEPT | Summary: Glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity with enables qualifier (UniRule/Rhea). Reason: GatB carries the catalytic sites for the EC 6.3.5.7 reaction itself, phosphorylating and amidating Glu-tRNA(Gln) with ammonia supplied by GatA. The standard applied across this batch is that a subunit that catalyses the ligase reaction may enable it (GatB), whereas a subunit that only supports it, by supplying a substrate or binding tRNA, contributes to it (GatA, GatC, CG3434). The contributes_to rows additionally record that the holoenzyme needs all three subunits. Supporting Evidence: file:DROME/GatB/GatB-uniprot.txt This subunit probably recognizes tRNA(Gln) file:DROME/GatB/GatB-deep-research-falcon.md depletion of GatCAB accumulated Glu–tRNA^Gln while mitochondrial tRNA^Glu remained aminoacylated |
| GO:0050567 glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity | ISS PMID:26761199 The aminoacyl-tRNA synthetases of Drosophila melanogaster. | ACCEPT | Summary: Contributes to glutaminyl-tRNA synthase (glutamine-hydrolyzing) activity. Reason: Core function; transamidation needs GatB together with GatA (ammonia) and GatC. Supporting Evidence: file:DROME/GatB/GatB-uniprot.txt This subunit probably recognizes tRNA(Gln) file:DROME/GatB/GatB-deep-research-falcon.md depletion of GatCAB accumulated Glu–tRNA^Gln while mitochondrial tRNA^Glu remained aminoacylated |
| GO:0070681 obsolete glutaminyl-tRNAGln biosynthesis via transamidation | IBA GO_REF:0000033 | MODIFY | Summary: Obsolete glutaminyl-tRNAGln biosynthesis via transamidation. Reason: The term was obsoleted with no automatic replacement. The subunit takes part in transamidation of misacylated Glu-tRNA(Gln) to Gln-tRNA(Gln), which is described by GO:0043685 conversion of glutamyl-tRNA to glutaminyl-tRNA. Propagation Review Root cause: SOURCE STALE OR MISSING Proposed replacements: conversion of glutamyl-tRNA to glutaminyl-tRNA Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
| GO:0070681 obsolete glutaminyl-tRNAGln biosynthesis via transamidation | IEA GO_REF:0000104 | MODIFY | Summary: Obsolete glutaminyl-tRNAGln biosynthesis via transamidation. Reason: The term was obsoleted with no automatic replacement. The subunit takes part in transamidation of misacylated Glu-tRNA(Gln) to Gln-tRNA(Gln), which is described by GO:0043685 conversion of glutamyl-tRNA to glutaminyl-tRNA. Propagation Review Root cause: SOURCE STALE OR MISSING Proposed replacements: conversion of glutamyl-tRNA to glutaminyl-tRNA Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
| GO:0070681 obsolete glutaminyl-tRNAGln biosynthesis via transamidation | ISS PMID:26761199 The aminoacyl-tRNA synthetases of Drosophila melanogaster. | MODIFY | Summary: Obsolete glutaminyl-tRNAGln biosynthesis via transamidation. Reason: The term was obsoleted with no automatic replacement. The subunit takes part in transamidation of misacylated Glu-tRNA(Gln) to Gln-tRNA(Gln), which is described by GO:0043685 conversion of glutamyl-tRNA to glutaminyl-tRNA. Propagation Review Root cause: SOURCE STALE OR MISSING Proposed replacements: conversion of glutamyl-tRNA to glutaminyl-tRNA Supporting Evidence: PMID:26761199 converting Glu to Gln via a heterotrimeric Glu-tRNAGln amidotransferase (Gat) |
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Download this section (compressed HTML)Q: Does fly GatB require GatA and GatC for stability in vivo, as for the human QRSL1/GATB/GATC complex?
Experiment: Measure mt-tRNA(Gln) aminoacylation identity and mitochondrial translation in GatB RNAi tissue.
Hypothesis: GatB knockdown causes accumulation of Glu-tRNA(Gln) in fly mitochondria.
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