Msed_0148 (A4YD23) notes: biotin carboxyl carrier protein (beta) subunit of acetyl-CoA/propionyl-CoA carboxylase

Automated deep research was unavailable for this gene (no -deep-research-*.md file). These notes
come from my own literature search (Europe PMC, cached papers in publications/) and the UniProt
record. Session date 2026-11-01.

Identity

• UniProt A4YD23 (TrEMBL), 167 aa, "Biotin carboxyl carrier protein", locus Msed_0148, keyword Biotin.
• C-terminal biotinyl/lipoyl domain (PS50968, 83-167; CDD cd06850 biotinyl_domain; Pfam Biotin_lipoyl).
  PANTHER PTHR45266:SF3 (named after oxaloacetate decarboxylase alpha chain; the family groups
  biotin-carrier domains generally). [file:METS5/Msed_0148/Msed_0148-uniprot.txt]
• My own sequence inspection: the biotin-acceptor lysine is predicted at K133 in ...SIEAMKSETIV...
  (A-M-K-S instead of the canonical A-M-K-M). This matches the published observation that Sulfolobales
  BCCPs have serine after the biotinylated lysine PMID:27315782.
• GOA has no rows for this protein.

The enzyme

• Beta subunit (18.6 kDa) of the M. sedula acetyl-CoA/propionyl-CoA carboxylase
  PMID:12581213.
• Autotrophic Sulfolobales contain large amounts of a small biotin-carrying protein
  PMID:9973333.
• A. brierleyi ortholog: biotin-binding site on the 20 kDa BCCP subunit PMID:12533469.
• M. sedula biotin protein ligase Msed_2010 biotinylates this subunit in vitro, and co-expressing it
  improved 3HP production in engineered P. furiosus PMID:27315782.
• Recombinant ACC-beta made in E. coli was poorly biotinylated; with Msed_2010 co-expressed in
  P. furiosus the purified recombinant ACC was active PMID:27315782.
• Gene induced 7-30-fold autotrophically together with Msed_0147 and Msed_1375 PMID:24532060.
• Expressed as part of E1 in P. furiosus (coupled E1αβ, Msed_0147-Msed_0148) PMID:23530213.

Subunit-level function and GO

BCCP carries the covalently bound biotin. BC carboxylates it, and the carboxybiotin arm moves to the
CT site, where the carboxyl group is transferred to acetyl-CoA or propionyl-CoA. BCCP thus supplies the
cofactor the reaction depends on: it does part of the work (the "cofactor" case in CLAUDE.md), so
contributes_to the overall activities and involvement in carbon fixation pass the participation test.

GO has no molecular-function term for "carboxyl carrier activity"; GO:0009374 biotin binding describes
non-covalent binding of free biotin and is not used for a covalently attached prosthetic group.
E. coli AccB is annotated enables GO:0003989 (IMP, IBA) and part_of GO:0009317. Here I use
contributes_to GO:0003989 and GO:0004658 (NEW, IDA from the purified complex, PMID:12581213) and
involved_in GO:0015977 carbon fixation. No CC term (see Msed_0147 notes on GO:0009317).

Open points

• No direct experiment (mass spectrometry or mutagenesis) has located the biotinylated lysine in
  M. sedula BCCP; K133 is a sequence-based prediction.
• NCBI esummary was down on 2026-11-01. PMID:12581213, PMID:9973333, PMID:12533469 and PMID:27315782 were
  cached with the repo's normal fetch pipeline, using metadata taken from efetch XML.