Recombinant Acidobacterium capsulatum NADH-quinone oxidoreductase subunit K (nuoK)
Description
Molecular and Functional Overview
Recombinant NADH-quinone oxidoreductase subunit K is derived from the gene nuoK (UniProt ID: C1F9D3) of Acidobacterium capsulatum, a Gram-negative bacterium known for its metabolic flexibility under microaerophilic and nanoxic conditions . The recombinant protein is produced in Escherichia coli with an N-terminal His tag, enabling purification via affinity chromatography. It spans 104 amino acids (aa) and retains full enzymatic activity when reconstituted .
Key roles in metabolism:
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Facilitates electron transfer from NADH to quinone in the respiratory chain, contributing to proton motive force generation .
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Part of the 14-subunit NADH:quinone oxidoreductase complex (NDH-I), essential for aerobic and microaerophilic respiration .
Metabolic Adaptation Under Oxygen Limitation
Studies on A. capsulatum reveal that nuoK-containing NDH-I is critical for maintaining redox balance under fluctuating oxygen levels :
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Respiratory flexibility: At nanomolar O₂ concentrations (0.1 µmol l⁻¹), A. capsulatum shifts from aerobic respiration to a respiro-fermentative strategy. NDH-I activity decreases, while non-proton-pumping NDH-II and bd-type oxidases are upregulated to mitigate NADH/NAD⁺ imbalance .
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Transcriptional regulation: The nuoK-associated operon (nuoA-N) shows reduced expression under low O₂, except for nuoABC, which remains active to sustain baseline electron transport .
Comparative Analysis With Other Complex I Systems
Table 2: Subunit Conservation in NADH Dehydrogenases
| Organism | Complex I Subunits | nuoK Homolog Presence | Reference |
|---|---|---|---|
| E. coli | 14 subunits | Yes (NDH-I) | |
| Rhodobacter capsulatus | 14 subunits | Yes (reverse activity) | |
| Acidobacterium capsulatum | 14 subunits | Yes |
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Functional divergence: Unlike mitochondrial complex I, bacterial NDH-I (including A. capsulatum) lacks supernumerary subunits but retains core proton-pumping machinery .
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Biotechnological utility: Recombinant nuoK enables structural studies of electron transport mechanisms and screens for respiratory inhibitors .
Technical Notes for Experimental Use
Product Specs
Note: We prioritize shipping the format currently in stock. However, should you have specific format requirements, please indicate them when placing your order, and we will accommodate your needs.
Note: All our proteins are shipped with standard blue ice packs. If you require dry ice shipping, please inform us in advance as additional fees will apply.
Target Background
KEGG: aca:ACP_0287
STRING: 240015.ACP_0287
