LPXD2 (At4g21220, F4JIP6) notes

Deep research could not be run (provider authentication fails in this
environment), so this summary was compiled manually from the cached full text of
Li et al. 2011 (PMID:21709257, PMC3136250), the UniProt record and PubMed
searches. No -deep-research-*.md file was produced.

Identity

• Swiss-Prot F4JIP6, "Probable UDP-3-O-acylglucosamine N-acyltransferase 2,
  mitochondrial" (AtLpxD2), 304 aa, predicted mitochondrial transit peptide 1-47.
  LpxD subfamily of the transferase hexapeptide repeat family; InterPro IPR007691;
  NCBIfam TIGR01853 lipid_A_lpxD; PANTHER PTHR43378:SF2.
• Paralog of LPXD1 (about 75% identical in our alignment; the paper says "more than
  60%") PMID:21709257.
• Keeps the acyl-ACP-binding arginine:
  PMID:21709257
  Our alignment (../LPXD1/LPXD1-bioinformatics/RESULTS.md) maps E. coli H239 to
  LPXD2 H216 and R293 to LPXD2 R270.

Mutant chemistry: LPXD2 is the main LpxD

• atlpxd2-1 (ET116191, CSHL gene trap, Landsberg erecta) is a homozygous null,
  compared with its Ler parent.
• PMID:21709257
  PMID:21709257
• PMID:21709257
• PMID:21709257
• PMID:21709257
• No visible phenotype:
  PMID:21709257
• Caveat: a single allele in a different accession from the other mutants; no
  complementation reported.

Localisation

• PMID:21709257
• Lipid X enriched in mitochondria:
  PMID:21709257
• Not chloroplast:
  PMID:21709257.

Other literature

• PubMed search "(LpxD OR lipid A OR lipid X) AND Arabidopsis" (2026-10-26):
  no further LpxD work. No in vitro assay or E. coli complementation of LPXD2
  has been published.
• Wei et al. 2020 (PMID:32470107) flagged the lipid A annotation; refuted for
  LPXD2 by the mutant chemistry above.

Paralog comparison

LPXD2 carries essentially all lipid X synthesis in seedlings; LPXD1 has no
detectable contribution, carries substitutions at substrate-binding residues and
may have a different acceptor. The two are therefore not redundant in the assay
conditions tested, and the reviews treat them differently: LpxD activity and lipid
A biosynthesis are accepted for LPXD2 and left undecided for LPXD1.

Review decisions (summary)

• LpxD activity GO:0103118 (IBA, IEA, IMP): ACCEPT, core. GO:0016747 MODIFY to
  GO:0103118.
• Lipid A biosynthetic process (IEA): ACCEPT, core, with the experimental
  evidence recorded on the row (a NEW row is not possible because the term is
  already in GOA). Obsolete lipid X metabolic process (IBA, IMP): MODIFY to
  lipid A biosynthetic process.
• Mitochondrion ACCEPT; cytoplasm MODIFY to mitochondrion; chloroplast REMOVE.