GLU1 (At5g04140, Q9ZNZ7) curation notes

Deep research could not be run in this environment (no provider API keys). These notes
are built only from cached publications (publications/PMID_*.md) and the UniProt record
(GLU1-uniprot.txt). No -deep-research-*.md file exists for this gene.

Identity

• Ferredoxin-dependent glutamate synthase 1 (Fd-GOGAT1; GLS1), 1622 aa with 105-aa transit
  peptide; glutamate synthase family; FMN and [3Fe-4S] cofactors by similarity (UniProt).
• Two Fd-GOGAT genes in Arabidopsis; only GLU1 is photorespiratory
  PMID:22303256.

Activity and process

• Reaction: L-glutamine + 2-oxoglutarate + 2 reduced ferredoxin -> 2 L-glutamate
  (EC 1.4.7.1; UniProt, ECO:0000269 PubMed:19223513).
• Photorespiratory role from gls mutants PMID:9596633;
  T-DNA knockout confirmation PMID:19223513.
• Also primary nitrogen assimilation in leaves PMID:9596633;
  glu1 mutant accumulates photorespiratory ammonium and amides PMID:19555410;
  PMID:20307264.
• Expression: leaf-predominant, induced by light and sucrose PMID:9596633;
  promoter active in mesophyll and phloem PMID:16034598.

Localization

• Chloroplast stroma (transit peptide; GFP; fractionation; stromal proteomes)
  PMID:19223513.
• Minor mitochondrial pool PMID:19223513,
  undetectable in FFE-purified mitochondria PMID:19223513
  PMID:22303256.

Non-catalytic role: SHMT1 support ("enzyme activator activity")

• PMID:19223513
• Catalysis not needed PMID:19223513.
• Assessment: genetic (glu1-201 L1270F retains Fd-GOGAT activity but loses SHMT activity and
  co-IP with SHMT1; catalytically dead internal deletion rescues), co-IP and BiFC evidence from
  one lab. No in vitro reconstitution of SHMT activation. GO:0008047 enzyme activator activity
  ("directly interacts with the enzyme, but does not result in a covalent modification") fits
  the claim; kept as non-core moonlighting function. The generic protein binding (IPI, SHM1)
  row was modified to this term.

Other

• ACR11 interacts with GLU1 in chloroplasts and controls Fd-GOGAT levels
  PMID:27411448.
• 14-3-3 omega TAP co-purification (PMID:19452453) is a high-throughput protein binding call;
  removed as uninformative.

Curation decisions (summary)

• Core MF GO:0016041 glutamate synthase (ferredoxin) activity; BP photorespiration,
  ammonia assimilation cycle, L-glutamate biosynthesis; CC chloroplast stroma.
• General MF terms (glutamate synthase activity, oxidoreductase terms) modified to GO:0016041.
• Mitochondrion/mitochondrial matrix and enzyme activator activity kept as non-core.
• Plasma membrane, chloroplast envelope, apoplast HDA marked over-annotated; mRNA binding
  marked over-annotated.
• No NEW annotations.