BCP belongs to the BCP/PrxQ subfamily of peroxiredoxins. Based on PubMed article retrieval, Nelson et al. (2011) PMID:21287625 established the PREX classification system defining six Prx subfamilies: AhpC/Prx1, BCP/PrxQ, Prx5, Prx6, Tpx, and AhpE. E. coli BCP is a founding member of the BCP/PrxQ subfamily.
Note on nomenclature: UniProt states "Belongs to the peroxiredoxin family. BCP/PrxQ subfamily." The PREX database (Soito et al. 2011, PMID:21036863) formally classifies Prx subfamilies. BCP/PrxQ is distinct from Prx5, though both can function as atypical 2-Cys Prxs.
"Thioredoxin-dependent hydroperoxide peroxidase activity of bacterioferritin comigratory protein (BCP) as a new member of the thiol-specific antioxidant protein (TSA)/Alkyl hydroperoxide peroxidase C (AhpC) family."
- First characterization of BCP as a thiol peroxidase
- Thioredoxin-dependent activity demonstrated
- BCP "preferentially reduced linoleic acid hydroperoxide rather than H(2)O(2) and t-butyl hydroperoxide"
- Cys-45 mutation (C45S) caused "complete loss of thiol peroxidase activity"
- BCP is a monomer; Cys-45 exists as cysteine sulfenic acid
- "BCP was induced 3-fold by the oxidative stress given by changing the growth conditions from the anaerobic to aerobic culture"
- bcp null mutant: "grew more slowly than its wild type in aerobic culture and showed the hypersensitivity toward various oxidants"
- IDA evidence for GO:0008379 thioredoxin peroxidase activity
- IMP evidence for GO:0006979 response to oxidative stress
"Interrogating the molecular details of the peroxiredoxin activity of the Escherichia coli bacterioferritin comigratory protein using high-resolution mass spectrometry."
- Classified E. coli BCP as an "atypical 2-Cys peroxiredoxin"
- "A transient sulfenic acid is initially formed on Cys-45, before resolution by the formation of an intramolecular disulfide bond between Cys-45 and Cys-50"
- C50S mutant "adopts a different and novel mechanistic pathway" -- intermolecular disulfide with second BCP molecule
- Both pathways are substrates for thioredoxin reduction
"Kinetic and thermodynamic features reveal that Escherichia coli BCP is an unusually versatile peroxiredoxin."
- BCP is a monomer by analytical ultracentrifugation (both oxidized and reduced)
- Uses multiple reducing substrates: Trx1, Trx2, Grx1, and Grx3
- "high redox potential of -145.9 +/- 3.2 mV, the highest to date observed for a Prx"
- "broad peroxide specificity, with comparable rates for H(2)O(2) and cumene hydroperoxide"
- pKa of ~5.8 for peroxidatic Cys45
- Nonsaturable interaction with Trx1 (Km > 100 uM), consistent with ping-pong mechanism
- BCP described as potentially "a defense enzyme of last resort" -- remains active under highly oxidizing conditions
- NOTE: This contradicts PMID:10644761 on substrate preference. Jeong et al. found preference for linoleic acid hydroperoxide; Reeves et al. found broad specificity with comparable rates for H2O2 and cumene hydroperoxide. Different assay conditions may explain this.
"Subdivision of the bacterioferritin comigratory protein family of bacterial peroxiredoxins based on catalytic activity."
- Subdivides BCP family into two classes: atypical 2-Cys (like E. coli BCP with resolving Cys) and 1-Cys (like B. cenocepacia BCP lacking resolving Cys)
- E. coli BCP uses atypical 2-Cys pathway (intramolecular disulfide Cys45-Cys50)
- 1-Cys BCPs prefer glutathione/glutaredoxin as redox partners; 2-Cys BCPs prefer thioredoxin
"A novel peroxiredoxin of the plant Sedum lineare is a homologue of Escherichia coli bacterioferritin co-migratory protein (Bcp)."
- Named the plant homolog "PrxQ" -- origin of the BCP/PrxQ subfamily name
- PrxQ complemented E. coli bcp mutant
- Two conserved cysteines (Cys-44, Cys-49) essential for activity
E. coli has three peroxiredoxins:
1. AhpC (AhpC/Prx1 subfamily) - the major scavenger of endogenous H2O2
2. Tpx (Tpx subfamily) - thiol peroxidase, primarily periplasmic
3. BCP (BCP/PrxQ subfamily) - versatile peroxiredoxin, cytosolic
BCP is distinct from AhpC in several ways: it is monomeric (AhpC forms decamers), has higher redox potential, broader substrate/reductant versatility, and lower abundance. The "enzyme of last resort" model (Reeves et al. 2011) suggests BCP may be particularly important under severe oxidative stress when other systems are comprommed.
The BioReason deep research file is reasonable but has several issues:
1. States BCP has "a preference for hydrogen peroxide" -- this is oversimplified. Jeong 2000 found preference for linoleic acid hydroperoxide; Reeves 2011 found broad specificity. The BioReason summary in the functional summary section correctly says "with a preference for hydrogen peroxide" but this is based on Reeves et al.'s findings at physiological Trx concentrations, not universal.
2. The "Functional coupling with alkyl hydroperoxide reductase complexes (AhpC/AhpF-type)" is speculative -- no direct evidence for coordination.
3. "Regulatory crosstalk with the accessory protein for GcvA" is speculative -- the bcp gene is adjacent to gcvR on the chromosome but no functional coupling is established.
4. The BioReason file has NO GO term predictions in the MF/BP/CC sections -- this is unusual.
5. The thinking trace is domain-architecture-focused and does a reasonable job connecting domains to function.