Recombinant Nostoc punctiforme Cytochrome b6 (petB)
Description
Functional Role in Photosynthesis
PetB is a core subunit of the cytochrome b6f complex (Cyt b6f), which mediates electron transfer between Photosystem II (PSII) and Photosystem I (PSI) and enables cyclic electron flow . Key functions include:
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Electron Transport: Facilitates plastoquinol oxidation and proton gradient generation via heme groups (b566 and b562) .
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State Transitions: Cyt b6f stability is essential for balancing energy distribution between PSI and PSII, as shown by destabilization in PetN-deficient mutants .
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Protein Interactions: PetB exhibits strong coevolution with PetD (subunit IV) (r = 0.89) and moderate correlation with PetA (r = 0.67), indicating functional interdependence .
Evolutionary Conservation
PetB in cyanobacteria shares high sequence identity with plastid-encoded homologs (mean substitution rate K = 0.1891 vs. 0.2073 in plastids) . This conservation underscores its indispensable role in oxygenic photosynthesis.
Complex Stability and Mutant Phenotypes
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PetN Dependency: Deletion of the small subunit PetN reduces Cyt b6f levels by 75–80%, impairing oxygen evolution and state transitions .
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Inhibitor Resistance: PetB mutants show partial insensitivity to DBMIB, a Cyt b6f inhibitor, due to altered plastoquinone pool dynamics .
Interaction Networks
Correlation analysis (r > 0.8) identifies PetB’s interaction partners:
| Subunit | Interaction Partner | Correlation Coefficient (r) |
|---|---|---|
| PetB | PetD (subunit IV) | 0.89 |
| PetB | PetA (cytochrome f) | 0.67 |
| PetB | NdhA (NADH dehydrogenase) | 0.82 |
These interactions suggest cross-complex coordination between photosynthetic and respiratory electron transport chains .
Recombinant Production
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Cloning: The petB gene (locus: Npun_F0310) is codon-optimized for E. coli expression .
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Purification: Affinity chromatography via His tag, followed by gel filtration for monomer isolation .
Research Applications
Product Specs
Please note that we will prioritize shipping the format currently in stock. However, if you have a specific format preference, kindly specify it in your order notes, and we will prepare your order accordingly.
All proteins are shipped with standard blue ice packs. If you require dry ice shipping, please contact us in advance, as additional fees will apply.
Generally, the shelf life of the liquid form is 6 months at -20°C/-80°C. For the lyophilized form, the shelf life is 12 months at -20°C/-80°C.
Target Background
KEGG: npu:Npun_F0310
STRING: 63737.Npun_F0310
