GLU1 (At5g04140; Fd-GOGAT1, GLS1) encodes the major ferredoxin-dependent glutamate synthase of Arabidopsis leaves, a large (about 1600 residue) FMN- and iron-sulfur-containing enzyme with an N-terminal chloroplast transit peptide. In the chloroplast stroma it transfers the amide nitrogen of glutamine to 2-oxoglutarate using electrons from reduced ferredoxin, producing two glutamate; together with plastidic glutamine synthetase GS2 it forms the GS/GOGAT cycle. GLU1 is the Fd-GOGAT isoform required for photorespiration: gls/glu1 mutants are chlorotic and accumulate ammonium and glutamine in air but are rescued by elevated CO2, while the paralog GLU2 acts mainly in roots. GLU1 also contributes to primary nitrogen assimilation in leaves, and its expression is highest in leaves and induced by light and sucrose. A small fraction of GLU1 is reported to be targeted to mitochondria, where it interacts with serine hydroxymethyltransferase SHM1 and is required, independently of its catalytic activity, for wild-type photorespiratory SHMT activity. In chloroplasts its abundance is controlled post-transcriptionally through interaction with the ACT-domain protein ACR11.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003729 mRNA binding | IDA PMID:32344669 Discovering the RNA-Binding Proteome of Plant Leaves with an... | MARK AS OVER ANNOTATED | Summary: GLU1 was among proteins captured by UV-crosslinking/oligo(dT) RNA interactome capture from Arabidopsis leaves. Reason: Proteome-wide RNA interactome capture recovers many abundant chloroplast metabolic enzymes lacking RNA-binding domains (Fd-GOGAT is about 1% of leaf protein). No study shows specific mRNA binding by GLU1 or a function for it; the capture is not evidence of an mRNA-binding function. Supporting Evidence: PMID:32344669 As has previously been reported for mammals, a large proportion of leaf RBPs lack known RNA-binding domains, suggesting unconventional modes of RNA binding. file:ARATH/GLU1/GLU1-uniprot.txt Belongs to the glutamate synthase family. |
| GO:0005515 protein binding | IPI PMID:19223513 Arabidopsis photorespiratory serine hydroxymethyltransferase... | MODIFY | Summary: Fd-GOGAT co-immunoprecipitated with SHMT1 (SHM1, Q9SZJ5) from purified leaf mitochondria and gave mitochondrial BiFC signal with SHM1. Reason: Generic protein binding is uninformative. The same paper shows that the GLU1-SHMT1 interaction is required for wild-type photorespiratory SHMT activity independently of Fd-GOGAT catalysis, which is what the more informative enzyme activator activity term (GO:0008047, already on the gene) expresses. Proposed replacements: enzyme activator activity Supporting Evidence: PMID:19223513 In the mitochondria, Fd-GOGAT interacts physically with SHMT1, and this interaction is necessary for photorespiratory SHMT activity. PMID:19223513 Thus, we conclude that wild-type levels of photorespiratory SHMT activity require Fd-GOGAT expression (although not catalytic activity) |
| GO:0005515 protein binding | IPI PMID:19452453 Proteomic profiling of tandem affinity purified 14-3-3 prote... | REMOVE | Summary: GLU1 was among 121 putative clients co-purified with TAP-tagged 14-3-3 omega (GRF2, At1g78300) in a proteomic screen. Reason: Generic protein binding from a high-throughput affinity-purification screen is uninformative; no functional consequence of a 14-3-3 interaction with Fd-GOGAT has been shown. Removal does not imply the co-purification is false. Supporting Evidence: PMID:19452453 The identification here of 121 putative clients provides support for in vivo 14-3-3 interactions with a diverse array of proteins |
| GO:0005739 mitochondrion | IDA PMID:19223513 Arabidopsis photorespiratory serine hydroxymethyltransferase... | KEEP AS NON CORE | Summary: Fd-GOGAT-GFP colocalized with MitoTracker and Fd-GOGAT was detected in Percoll-purified mitochondrial fractions. Reason: Jamai et al. showed mitochondrial GFP signal and Fd-GOGAT immunodetection in Percoll-purified mitochondria, and genetic evidence (M1K/M3I start-codon variants) that a mitochondrial pool is needed for photorespiratory SHMT activity. FFE-purified mitochondria and matrix proteomes did not detect Fd-GOGAT, so the pool is at most small. The localization is supported for the SHMT1-related role but is not the location of the core catalytic function. Supporting Evidence: PMID:19223513 We show that Fd-GOGAT is dual targeted to the mitochondria and the chloroplasts. PMID:19223513 Fd-GOGAT was detected by protein gel blot analysis of wild-type Col seedlings in both chloroplastic and mitochondrial fractions ( Figure 3B ). PMID:19223513 FFE-purified Col-0 shoot mitochondria and Landsberg erecta tissue culture mitochondria do not contain sufficient amounts of Fd-GOGAT to be detected by mass spectrometry or by protein gel blots using Fd-GOGAT antibodies |
| GO:0005759 mitochondrial matrix | EXP PMID:19223513 Arabidopsis photorespiratory serine hydroxymethyltransferase... | KEEP AS NON CORE | Summary: Mitochondrial Fd-GOGAT co-immunoprecipitated with the matrix enzyme SHMT1 from purified leaf mitochondria. Reason: Jamai et al. showed mitochondrial GFP signal and Fd-GOGAT immunodetection in Percoll-purified mitochondria, and genetic evidence (M1K/M3I start-codon variants) that a mitochondrial pool is needed for photorespiratory SHMT activity. FFE-purified mitochondria and matrix proteomes did not detect Fd-GOGAT, so the pool is at most small. The localization is supported for the SHMT1-related role but is not the location of the core catalytic function. The matrix assignment rests on interaction with the matrix enzyme SHMT1 rather than on sub-mitochondrial fractionation. Supporting Evidence: PMID:19223513 In the mitochondria, Fd-GOGAT interacts physically with SHMT1, and this interaction is necessary for photorespiratory SHMT activity. PMID:19223513 FFE-purified Col-0 shoot mitochondria and Landsberg erecta tissue culture mitochondria do not contain sufficient amounts of Fd-GOGAT to be detected by mass spectrometry or by protein gel blots using Fd-GOGAT antibodies PMID:22303256 This at least implies that the proteins are scarce in the mitochondrion which would again support a regulatory instead of a catalytic role. |
| GO:0005759 mitochondrial matrix | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt SubCell mapping of curated "Mitochondrion matrix" from Jamai et al. 2009. Reason: Jamai et al. showed mitochondrial GFP signal and Fd-GOGAT immunodetection in Percoll-purified mitochondria, and genetic evidence (M1K/M3I start-codon variants) that a mitochondrial pool is needed for photorespiratory SHMT activity. FFE-purified mitochondria and matrix proteomes did not detect Fd-GOGAT, so the pool is at most small. The localization is supported for the SHMT1-related role but is not the location of the core catalytic function. Supporting Evidence: PMID:19223513 In the mitochondria, Fd-GOGAT interacts physically with SHMT1, and this interaction is necessary for photorespiratory SHMT activity. PMID:19223513 FFE-purified Col-0 shoot mitochondria and Landsberg erecta tissue culture mitochondria do not contain sufficient amounts of Fd-GOGAT to be detected by mass spectrometry or by protein gel blots using Fd-GOGAT antibodies |
| GO:0005886 plasma membrane | HDA PMID:28887381 Global Analysis of Membrane-associated Protein Oligomerizati... | MARK AS OVER ANNOTATED | Summary: Detected in membrane-associated fractions in a size-exclusion/MS correlation profiling study. Reason: Fd-GOGAT is a soluble stromal enzyme with a chloroplast transit peptide and no transmembrane segment; there is no evidence for plasma membrane association. The study reports extensive partitioning of soluble proteins into membrane fractions. Not removed because the dataset-level assignment was not inspected. Supporting Evidence: PMID:28887381 Over 150 proteins had a complicated localization pattern, and were clearly partitioned between cytosolic and membrane-associated pools. PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. |
| GO:0008047 enzyme activator activity | IDA PMID:19223513 Arabidopsis photorespiratory serine hydroxymethyltransferase... | KEEP AS NON CORE | Summary: The glu1-201 (L1270F) allele retains Fd-GOGAT activity but loses SHMT1 interaction and photorespiratory SHMT activity; a catalytically dead internal deletion (glu1 204) still interacts with SHMT1 and restores SHMT activity. Reason: Genetic and co-immunoprecipitation evidence that GLU1 protein, through direct interaction, is needed for wild-type SHMT1 activity in mitochondria, independent of its glutamate synthase activity. This fits the GO definition (direct interaction, no covalent modification), but rests on one study, direct activation of purified SHMT1 by Fd-GOGAT has not been reconstituted in vitro, and the mitochondrial pool is small and disputed. Kept as a non-core moonlighting function. Supporting Evidence: PMID:19223513 In the mitochondria, Fd-GOGAT interacts physically with SHMT1, and this interaction is necessary for photorespiratory SHMT activity. PMID:19223513 Thus, we conclude that wild-type levels of photorespiratory SHMT activity require Fd-GOGAT expression (although not catalytic activity) PMID:22303256 This at least implies that the proteins are scarce in the mitochondrion which would again support a regulatory instead of a catalytic role. |
| GO:0009416 response to light stimulus | IEP PMID:16034598 Expression of a ferredoxin-dependent glutamate synthase gene... | KEEP AS NON CORE | Summary: The GLU1 promoter drove GUS expression in tobacco that was induced by white light, red light or sucrose, mirroring GLU1 mRNA induction in Arabidopsis. Reason: Light induction of GLU1 expression is well documented and fits its photorespiratory and photosynthetic nitrogen-assimilation role, but expression regulation is not a function of the gene product. Non-core. Supporting Evidence: PMID:16034598 White light, red light or sucrose induced GUS expression in the dark-grown seedlings in a pattern similar to the GLU1 mRNA accumulation in Arabidopsis. |
| GO:0009416 response to light stimulus | IEP PMID:9596633 Arabidopsis gls mutants and distinct Fd-GOGAT genes. Implica... | KEEP AS NON CORE | Summary: GLU1 mRNA, highest in leaves, is specifically induced by light. Reason: Expression response to light; true but peripheral to the enzymatic role. Supporting Evidence: PMID:9596633 GLU1 mRNA was expressed at the highest levels in leaves, and its mRNA levels were specifically induced by light or sucrose. |
| GO:0009507 chloroplast | HDA PMID:18431481 Sorting signals, N-terminal modifications and abundance of t... | ACCEPT | Summary: Identified in large-scale MS analysis of purified chloroplasts. Reason: Fd-GOGAT is a chloroplast stromal enzyme (transit peptide; GFP; organelle fractionation; stromal proteomes). Accepted; the sub-organellar stroma term is also accepted as core. Supporting Evidence: PMID:18431481 Here we present a large scale analysis by nanoLC-Q-TOF and nanoLC-LTQ-Orbitrap mass spectrometry (MS) of ten independent chloroplast preparations from Arabidopsis thaliana which unambiguously identified 1325 proteins. PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. |
| GO:0009507 chloroplast | HDA PMID:25293756 A proteomic strategy for global analysis of plant protein co... | ACCEPT | Summary: Detected in subcellular-fraction size-exclusion/MS profiling of leaf protein complexes. Reason: Fd-GOGAT is a chloroplast stromal enzyme (transit peptide; GFP; organelle fractionation; stromal proteomes). Accepted; the sub-organellar stroma term is also accepted as core. Supporting Evidence: PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. PMID:19223513 Fd-GOGAT was detected by protein gel blot analysis of wild-type Col seedlings in both chloroplastic and mitochondrial fractions ( Figure 3B ). |
| GO:0009507 chloroplast | IDA PMID:19223513 Arabidopsis photorespiratory serine hydroxymethyltransferase... | ACCEPT | Summary: Fd-GOGAT-GFP showed chloroplastic localization and Fd-GOGAT was detected in chloroplast fractions. Reason: Fd-GOGAT is a chloroplast stromal enzyme (transit peptide; GFP; organelle fractionation; stromal proteomes). Accepted; the sub-organellar stroma term is also accepted as core. Supporting Evidence: PMID:19223513 Fd-GOGAT was detected by protein gel blot analysis of wild-type Col seedlings in both chloroplastic and mitochondrial fractions ( Figure 3B ). PMID:19223513 We show that Fd-GOGAT is dual targeted to the mitochondria and the chloroplasts. |
| GO:0009507 chloroplast | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA-based chloroplast assignment. Reason: Fd-GOGAT is a chloroplast stromal enzyme (transit peptide; GFP; organelle fractionation; stromal proteomes). Accepted; the sub-organellar stroma term is also accepted as core. Supporting Evidence: PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. |
| GO:0009507 chloroplast | ISM GO_REF:0000122 | ACCEPT | Summary: AtSubP prediction from the N-terminal transit peptide. Reason: Fd-GOGAT is a chloroplast stromal enzyme (transit peptide; GFP; organelle fractionation; stromal proteomes). Accepted; the sub-organellar stroma term is also accepted as core. Supporting Evidence: PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. |
| GO:0009570 chloroplast stroma | HDA PMID:16207701 The oligomeric stromal proteome of Arabidopsis thaliana chlo... | ACCEPT | Summary: Identified in the oligomeric stromal proteome of purified chloroplasts. Reason: Fd-GOGAT is a soluble stromal enzyme that functions with GS2 in the stromal GS/GOGAT cycle, using photosynthetically reduced ferredoxin. Core location. Supporting Evidence: PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0009570 chloroplast stroma | HDA PMID:18633119 Quantitative proteomics of a chloroplast SRP54 sorting mutan... | ACCEPT | Summary: Quantified in chloroplast proteomes of wild type and the cpSRP54 mutant. Reason: Fd-GOGAT is a soluble stromal enzyme that functions with GS2 in the stromal GS/GOGAT cycle, using photosynthetically reduced ferredoxin. Core location. Supporting Evidence: PMID:18633119 a quantitative comparison of ffc2-1 was carried out for total leaf proteomes of young seedlings and for chloroplast proteomes of fully developed leaves PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. |
| GO:0009570 chloroplast stroma | HDA PMID:20061580 AT_CHLORO, a comprehensive chloroplast proteome database wit... | ACCEPT | Summary: Assigned to stroma in the AT_CHLORO subplastidial proteome. Reason: Fd-GOGAT is a soluble stromal enzyme that functions with GS2 in the stromal GS/GOGAT cycle, using photosynthetically reduced ferredoxin. Core location. Supporting Evidence: PMID:20061580 We went a step further into the knowledge of the chloroplast proteome by focusing, in the same set of experiments, on the localization of proteins in the stroma, the thylakoids, and envelope membranes. |
| GO:0009570 chloroplast stroma | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt SubCell mapping of curated "Plastid, chloroplast stroma". Reason: Fd-GOGAT is a soluble stromal enzyme that functions with GS2 in the stromal GS/GOGAT cycle, using photosynthetically reduced ferredoxin. Core location. Supporting Evidence: PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0009744 response to sucrose | IEP PMID:9596633 Arabidopsis gls mutants and distinct Fd-GOGAT genes. Implica... | KEEP AS NON CORE | Summary: GLU1 mRNA in leaves is specifically induced by sucrose. Reason: Sucrose induction of GLU1 expression links it to carbon-nitrogen coordination and primary nitrogen assimilation, but is an expression response rather than a function of the protein. Non-core. Supporting Evidence: PMID:9596633 GLU1 mRNA was expressed at the highest levels in leaves, and its mRNA levels were specifically induced by light or sucrose. PMID:9596633 Both the mutant analysis and gene regulation studies suggest that GLU1 plays a major role in photorespiration and also plays a role in primary nitrogen assimilation in leaves |
| GO:0009853 photorespiration | IMP PMID:19223513 Arabidopsis photorespiratory serine hydroxymethyltransferase... | ACCEPT | Summary: glu1 loss-of-function (glu1-202) and glu1-201 mutants show photorespiratory chlorosis at ambient CO2, rescued by wild-type GLU1. Reason: GLU1 catalyses the glutamate synthase step of photorespiratory ammonia refixation, and its loss gives the classic high-CO2-rescuable photorespiratory phenotype; it additionally supports mitochondrial SHMT1 activity. Core process. Supporting Evidence: PMID:19223513 We confirmed that a T-DNA insertion mutant (Salk_104286, termed glu1-202 ), in which the T-DNA has inserted into the 2nd exon of GLU1 , lacks Fd-GOGAT protein ( Figure 3A ) and exhibits reduced Fd-GOGAT activity ( Table 1 ) and photorespiratory chlorosis PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. PMID:22303256 Arabidopsis contains two expressed genes for Fd-GOGAT ( Glu 1 (At5g04140) and Glu 2 (At2g41220)), but only mutation of the Glu 1 gene resulted in a photorespiratory phenotype ( Coschigano et al., 1998 ). |
| GO:0009853 photorespiration | TAS PMID:9596633 Arabidopsis gls mutants and distinct Fd-GOGAT genes. Implica... | ACCEPT | Summary: Coschigano et al. linked the gls1 photorespiratory locus to GLU1, the leaf light-induced Fd-GOGAT gene. Reason: Core photorespiratory role of GLU1, established by gls mutants mapping to GLU1. Supporting Evidence: PMID:9596633 Ferredoxin-dependent glutamate synthase (Fd-GOGAT) plays a major role in photorespiration in Arabidopsis, as has been determined by the characterization of mutants deficient in Fd-GOGAT enzyme activity (gls). PMID:9596633 Both the mutant analysis and gene regulation studies suggest that GLU1 plays a major role in photorespiration and also plays a role in primary nitrogen assimilation in leaves |
| GO:0009941 chloroplast envelope | HDA PMID:12938931 Proteomic study of the Arabidopsis thaliana chloroplastic en... | MARK AS OVER ANNOTATED | Summary: Detected in a proteome of "mixed" chloroplast envelope membranes. Reason: Fd-GOGAT is an abundant soluble stromal enzyme; envelope preparations commonly contain stromal contaminants. Not a functional location. Supporting Evidence: PMID:12938931 "mixed" envelopes were subsequently isolated using sucrose step gradients PMID:16207701 This study presents an analysis of the stromal proteome in its oligomeric state extracted from highly purified chloroplasts of Arabidopsis thaliana. |
| GO:0015930 glutamate synthase activity | IBA GO_REF:0000033 | MODIFY | Summary: PAINT inference of glutamate synthase activity for the glutamate synthase family node; GLU1 (AT5G04140) is among the experimentally characterized descendants. Reason: Correct but general: the family node covers both NADH- and ferredoxin-dependent GOGATs. GLU1 is specifically the ferredoxin-dependent enzyme (GO:0016041), which the gene already carries. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN000234342 · PTN000234342 SUPPORTS TRANSFER Node correctly places GLU1 among glutamate synthases; the node term is the parent of the ferredoxin-specific activity supported for GLU1. Proposed replacements: glutamate synthase (ferredoxin) activity Supporting Evidence: file:ARATH/GLU1/GLU1-uniprot.txt Reaction=2 oxidized [2Fe-2S]-[ferredoxin] + 2 L-glutamate = L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] + 2-oxoglutarate + 2 H(+) file:ARATH/GLU1/GLU1-uniprot.txt Belongs to the glutamate synthase family. |
| GO:0015930 glutamate synthase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapping from glutamate synthase domains. Reason: Correct but general; GLU1 is ferredoxin-dependent (GO:0016041), already carried by the gene. Proposed replacements: glutamate synthase (ferredoxin) activity Supporting Evidence: file:ARATH/GLU1/GLU1-uniprot.txt Reaction=2 oxidized [2Fe-2S]-[ferredoxin] + 2 L-glutamate = L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] + 2-oxoglutarate + 2 H(+) file:ARATH/GLU1/GLU1-uniprot.txt Belongs to the glutamate synthase family. |
| GO:0016041 glutamate synthase (ferredoxin) activity | IDA PMID:19223513 Arabidopsis photorespiratory serine hydroxymethyltransferase... | ACCEPT | Summary: Fd-GOGAT activity was measured in wild type and glu1 alleles; glu1-202 knockout lacks the protein and has reduced Fd-GOGAT activity, restored by GLU1. Reason: GLU1 encodes the major leaf ferredoxin-dependent glutamate synthase; glu1 mutants lack most Fd-GOGAT activity. Core activity. Supporting Evidence: PMID:19223513 We confirmed that a T-DNA insertion mutant (Salk_104286, termed glu1-202 ), in which the T-DNA has inserted into the 2nd exon of GLU1 , lacks Fd-GOGAT protein ( Figure 3A ) and exhibits reduced Fd-GOGAT activity ( Table 1 ) and photorespiratory chlorosis file:ARATH/GLU1/GLU1-uniprot.txt Reaction=2 oxidized [2Fe-2S]-[ferredoxin] + 2 L-glutamate = L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] + 2-oxoglutarate + 2 H(+) |
| GO:0016041 glutamate synthase (ferredoxin) activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA (EC 1.4.7.1, RHEA:12128). Reason: GLU1 encodes the major leaf ferredoxin-dependent glutamate synthase; glu1 mutants lack most Fd-GOGAT activity. Core activity. Supporting Evidence: file:ARATH/GLU1/GLU1-uniprot.txt Reaction=2 oxidized [2Fe-2S]-[ferredoxin] + 2 L-glutamate = L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] + 2-oxoglutarate + 2 H(+) file:ARATH/GLU1/GLU1-uniprot.txt Belongs to the glutamate synthase family. |
| GO:0016041 glutamate synthase (ferredoxin) activity | ISS PMID:9596633 Arabidopsis gls mutants and distinct Fd-GOGAT genes. Implica... | ACCEPT | Summary: Coschigano et al. identified GLU1 and GLU2 as the two expressed Fd-GOGAT genes by sequence similarity. Reason: GLU1 encodes the major leaf ferredoxin-dependent glutamate synthase; glu1 mutants lack most Fd-GOGAT activity. Core activity. Supporting Evidence: PMID:9596633 Ferredoxin-dependent glutamate synthase (Fd-GOGAT) plays a major role in photorespiration in Arabidopsis, as has been determined by the characterization of mutants deficient in Fd-GOGAT enzyme activity (gls). |
| GO:0016491 oxidoreductase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapping from the glutamate synthase alpha subunit C-terminal domain. Reason: Correct but uninformative; replace with the specific glutamate synthase (ferredoxin) activity already carried by the gene. Proposed replacements: glutamate synthase (ferredoxin) activity Supporting Evidence: file:ARATH/GLU1/GLU1-uniprot.txt Reaction=2 oxidized [2Fe-2S]-[ferredoxin] + 2 L-glutamate = L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] + 2-oxoglutarate + 2 H(+) |
| GO:0016638 oxidoreductase activity, acting on the CH-NH2 group of donors | IEA GO_REF:0000002 | MODIFY | Summary: InterPro2GO mapping from the glutamate synthase domain. Reason: Correct but general; GO:0016041 is the specific descendant supported for GLU1. Proposed replacements: glutamate synthase (ferredoxin) activity Supporting Evidence: file:ARATH/GLU1/GLU1-uniprot.txt Reaction=2 oxidized [2Fe-2S]-[ferredoxin] + 2 L-glutamate = L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] + 2-oxoglutarate + 2 H(+) |
| GO:0019676 ammonia assimilation cycle | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference of ammonia assimilation cycle for the glutamate synthase family node. Reason: Fd-GOGAT is the GOGAT half of the GS/GOGAT ammonia assimilation cycle; GLU1 acts in both photorespiratory refixation and primary leaf nitrogen assimilation. Core process. Supporting Evidence: PMID:22303256 Re-assimilation of NH 3 takes place in the chloroplast through the sequential action of two enzymes, glutamine synthetase (GS; EC 6.1.3.2) and ferredoxin-dependent glutamine:oxoglutarate aminotransferase PMID:9596633 Both the mutant analysis and gene regulation studies suggest that GLU1 plays a major role in photorespiration and also plays a role in primary nitrogen assimilation in leaves PMID:19555410 Phenotypic analysis revealed a high level of photorespiratory ammonium, glutamine/glutamate and asparagine/aspartate in the GLU1 mutant lacking the major ferredoxin-glutamate synthase |
| GO:0048046 apoplast | HDA PMID:18538804 Hydroponic isotope labelling of entire plants (HILEP) for qu... | MARK AS OVER ANNOTATED | Summary: Detected in an apoplast-oriented quantitative proteomics dataset under oxidative stress. Reason: Fd-GOGAT has a chloroplast transit peptide and no secretion signal; detection in apoplastic extracts most likely reflects contamination by abundant stromal proteins. Supporting Evidence: PMID:18538804 it was possible to show differential protein expression in the apoplast of plants submitted to oxidative stress. PMID:19223513 Fd-GOGAT is a chloroplastic enzyme responsible for the reassimilation of photorespiratory ammonia as well as for primary nitrogen assimilation. |
| GO:0097054 L-glutamate biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT inference of L-glutamate biosynthetic process. Reason: Fd-GOGAT produces two glutamate from glutamine and 2-oxoglutarate; glu1 mutants accumulate glutamine. Core process. Supporting Evidence: file:ARATH/GLU1/GLU1-uniprot.txt Involved in glutamate biosynthesis in leaf. Required for the reassimilation of ammonium ions generated during photorespiration. PMID:20307264 An elevated glutamine level in the glu1-2 mutant was the most prominent of these changes. |
| GO:0097054 L-glutamate biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from InterPro and UniPathway UPA00634. Reason: Fd-GOGAT produces two glutamate from glutamine and 2-oxoglutarate; glu1 mutants accumulate glutamine. Core process. Supporting Evidence: file:ARATH/GLU1/GLU1-uniprot.txt Involved in glutamate biosynthesis in leaf. Required for the reassimilation of ammonium ions generated during photorespiration. file:ARATH/GLU1/GLU1-uniprot.txt Reaction=2 oxidized [2Fe-2S]-[ferredoxin] + 2 L-glutamate = L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] + 2-oxoglutarate + 2 H(+) |
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Download this section (compressed HTML)Q: How does mitochondrial Fd-GOGAT increase SHMT1 activity mechanistically (allosteric activation, complex stabilization, substrate channelling), and is the effect reproducible with purified proteins?
Q: How large is the mitochondrial pool of GLU1 in wild-type leaves, given that it is undetectable in FFE-purified mitochondria?
Q: Does ACR11 regulate Fd-GOGAT activity directly (allosterically, via glutamine binding) as well as its protein level?
Experiment: Reconstitute purified SHMT1 with wild-type, L1270F and catalytically dead Fd-GOGAT in vitro and measure SHMT kinetics to test direct activation.
Experiment: Native-promoter epitope-tagged GLU1 in glu1 background, with FFE-purified mitochondria and protease-protection assays, to quantify the mitochondrial pool and its sub-mitochondrial location.
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