Recombinant Bacillus subtilis ATP synthase subunit a (atpB)
Description
Introduction to Bacillus subtilis ATP Synthase Subunit a (atpB)
Bacillus subtilis ATP synthase subunit a (atpB) is a membrane-embedded component of the F0 sector of the F0F1 ATP synthase complex. This protein is encoded within a nine-gene operon responsible for producing the complete ATP synthase machinery. The arrangement of these genes in B. subtilis is identical to that found in Escherichia coli and three other Bacillus species, highlighting the evolutionary conservation of this essential energy-generating complex . The atpB gene specifically encodes the a-subunit, which is also known as ATP synthase F0 sector subunit a or F-ATPase subunit 6 .
The complete F0F1 ATP synthase functions as a molecular motor that harnesses the energy of proton flow across the membrane to synthesize adenosine triphosphate (ATP), the universal energy currency of cells. Within this complex, the a-subunit (atpB) forms part of the membrane-embedded proton channel and plays a crucial role in converting the proton motive force into mechanical energy that drives ATP synthesis .
Physicochemical Properties
The recombinant form of atpB is typically produced with an N-terminal histidine tag to facilitate purification . This modification, while not affecting the fundamental structure of the protein, provides a convenient means for isolation from expression systems. The recombinant protein exhibits the following key properties:
Table 1: Physicochemical Properties of Recombinant B. subtilis atpB Protein
| Property | Characteristic |
|---|---|
| Length | 244 amino acids (native sequence) |
| Tag | N-terminal histidine tag (recombinant form) |
| Hydrophobicity | High (multiple transmembrane segments) |
| Origin | Bacillus subtilis |
| Function | Proton channel component of F0F1 ATP synthase |
| UniProt ID | P37813 |
| Synonyms | ATP synthase subunit a, ATP synthase F0 sector subunit a, F-ATPase subunit 6 |
This highly hydrophobic protein requires special handling conditions due to its membrane-associated nature, including the use of detergents for solubilization during purification procedures .
Expression Systems
While B. subtilis itself is recognized as an excellent host for recombinant protein production due to its GRAS (Generally Recognized As Safe) status and natural ability to incorporate exogenous DNA , the recombinant atpB protein is frequently expressed in Escherichia coli expression systems . This approach leverages the well-established protocols and high protein yields achievable with E. coli while allowing researchers to study the B. subtilis protein in isolation.
The expression of membrane proteins like atpB presents particular challenges due to their hydrophobic nature and tendency to form inclusion bodies when overexpressed. Specialized expression vectors and carefully optimized conditions are necessary to ensure proper folding and membrane integration .
Purification Strategies
The recombinant B. subtilis atpB protein, when expressed with an N-terminal histidine tag, can be purified using immobilized metal affinity chromatography (IMAC) . Following purification, the protein is typically lyophilized to form a powder, which can be reconstituted for experimental use. The recommended reconstitution procedure involves:
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Brief centrifugation of the vial prior to opening
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Reconstitution in deionized sterile water to a concentration of 0.1-1.0 mg/mL
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Addition of 5-50% glycerol (final concentration) for long-term storage
The purified protein requires careful storage conditions, with recommended storage at -20°C/-80°C upon receipt. Working aliquots can be maintained at 4°C for up to one week, but repeated freezing and thawing should be avoided to maintain protein integrity .
Role in Energy Metabolism
The atpB protein plays a critical role in the bioenergetics of B. subtilis by forming part of the proton channel in the F0 sector of ATP synthase. This channel allows protons to flow down their electrochemical gradient across the membrane, driving the rotary motion that powers ATP synthesis in the F1 sector .
Research with B. subtilis strains containing deletions in the atp operon has demonstrated the essential nature of ATP synthase for efficient energy metabolism. These mutant strains exhibit:
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Inability to grow with succinate as the sole carbon and energy source
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Decreased growth yield (43-56% of wild-type levels)
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Reduced growth rate (61-66% of wild-type levels)
These findings highlight the crucial role of the ATP synthase complex, including the atpB subunit, in oxidative phosphorylation and energy production in B. subtilis.
Metabolic Adaptations in ATP Synthase-Deficient Strains
In the absence of functional ATP synthase, B. subtilis cells adapt by increasing substrate-level phosphorylation for ATP generation. This metabolic shift is evidenced by:
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Twofold increase in byproduct formation (mainly acetate)
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Increased glycolytic flux
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Enhanced NADH synthesis
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Stimulation of respiration rate
These compensatory mechanisms demonstrate the metabolic flexibility of B. subtilis but cannot fully replace the efficient energy generation provided by the complete ATP synthase complex that includes the atpB subunit.
Drug Development
As a component of an essential metabolic complex, the atpB protein represents a potential target for antimicrobial drug development. Compounds that specifically inhibit the function of bacterial ATP synthase could disrupt energy metabolism and potentially serve as novel antibiotics. The availability of purified recombinant atpB facilitates:
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High-throughput screening of chemical libraries
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Structure-based drug design
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Validation of potential inhibitors
Biotechnological Applications
The technologies developed for expressing and purifying recombinant B. subtilis proteins like atpB contribute to the broader field of protein production. B. subtilis itself has emerged as an important expression system for various biotechnological applications due to:
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Its GRAS (Generally Recognized As Safe) status
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Natural capacity to absorb and incorporate exogenous DNA
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Ability to secrete proteins into the extracellular medium
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Well-characterized genetics and molecular biology
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Availability of various inducible and constitutive promoter systems
These characteristics have established B. subtilis as a powerful bacterial host for both academic research and industrial protein production, including the expression of membrane proteins like atpB .
Comparison with ATP Synthase from Other Organisms
The ATP synthase complex, including the atpB subunit, displays remarkable evolutionary conservation across different species. Studies of the B. subtilis atp operon have revealed that:
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The arrangement of genes in the operon is identical to that found in E. coli and three other Bacillus species
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The deduced amino acid sequences of the nine subunits show significant similarity to their counterparts from other organisms
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The functional responses to the absence of oxidative phosphorylation are similar in B. subtilis and E. coli
This conservation reflects the fundamental importance of ATP synthase in cellular bioenergetics across diverse bacterial species and provides valuable comparative information for understanding the structure-function relationships of these proteins.
Product Specs
Note: We prioritize shipping the format we have in stock. However, if you have specific format requirements, please indicate them during order placement. We will fulfill your requests whenever possible.
Note: All our proteins are shipped with standard blue ice packs. If you require dry ice shipping, please inform us in advance. Additional charges will apply.
Generally, the shelf life of liquid form is 6 months at -20°C/-80°C. The shelf life of lyophilized form is 12 months at -20°C/-80°C.
Target Background
KEGG: bsu:BSU36870
STRING: 224308.Bsubs1_010100019936
Q&A
What is the function of ATP synthase subunit a (atpB) in Bacillus subtilis?
ATP synthase subunit a (atpB) is a critical component of the F0 portion of the F0F1 ATP synthase complex in B. subtilis. This membrane-embedded protein facilitates proton translocation across the cell membrane, which drives the rotary mechanism required for ATP synthesis during oxidative phosphorylation.
Studies with B. subtilis atp operon deletion mutants demonstrate that cells lacking functional ATP synthase are unable to grow with succinate as the sole carbon and energy source . These mutants can only synthesize ATP through substrate-level phosphorylation, resulting in a twofold decrease in intracellular ATP/ADP ratio . This energy deficit leads to decreased growth yield (43-56% of wild-type levels) and reduced growth rates (61-66% of wild-type), highlighting the essential role of ATP synthase in cellular energetics .
How is the atpB gene organized within the ATP synthase operon in B. subtilis?
The atpB gene is part of an operon containing nine genes that encode for the subunits of B. subtilis F0F1 ATP synthase . The arrangement of these genes in B. subtilis is identical to that found in Escherichia coli and three other Bacillus species, suggesting evolutionary conservation of this genetic organization . The high degree of amino acid sequence similarity between the B. subtilis ATP synthase subunits and their counterparts in other organisms indicates functional conservation across diverse bacterial species .
What is the amino acid sequence and structural characteristics of B. subtilis ATP synthase subunit a?
According to the research data, the full-length B. subtilis ATP synthase subunit a (atpB) protein consists of 244 amino acids . The N-terminal sequence begins with: MNHGYRTIEFLGLTFNLTNILMITVASVIVLLIAILTTRTLSIRPGKAQNFMEWIVDFVRNIIGSTMDLKTGANFLALGVTLLMYI .
Table 1: Properties of B. subtilis ATP synthase subunit a (atpB)
| Property | Details |
|---|---|
| Length | 244 amino acids |
| UniProt ID | P37813 |
| N-terminal sequence | MNHGYRTIEFLGLTFNLTNILMITVASVIVLLIAILTTRTLSIRPGKAQNFMEWIVDFVR NIIGSTMDLKTGANFLALGVTLLMYI... |
| Predicted topology | Multiple transmembrane domains |
| Expression system for recombinant protein | E. coli |
| Common tag for purification | N-terminal His-tag |
What are the optimal methods for expressing and purifying recombinant B. subtilis atpB?
Successful expression and purification of recombinant B. subtilis atpB requires careful consideration of its membrane-associated nature. Based on published research, the following methodological approach has proven effective:
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Expression system selection: E. coli has been successfully used as a heterologous host for expressing full-length B. subtilis atpB (1-244aa) .
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Construct design: Fusion of an N-terminal His-tag to the atpB protein facilitates downstream purification while maintaining protein functionality .
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Expression conditions: Optimizing temperature, induction timing, and media composition is critical for maximizing membrane protein expression while minimizing formation of inclusion bodies.
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Extraction and solubilization: Membrane proteins like atpB typically require detergent solubilization. A two-step extraction process is recommended: initial cell lysis followed by membrane fraction isolation and detergent solubilization.
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Purification strategy: Immobilized metal affinity chromatography (IMAC) using the His-tag, followed by size exclusion chromatography to remove aggregates and achieve high purity.
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Stabilization: Final formulation as a lyophilized powder maintains protein stability during storage .
How can researchers assess the functional activity of recombinant atpB after purification?
Assessing the functional activity of recombinant atpB presents unique challenges due to its role as part of a multisubunit complex. The following methodological approaches can be employed:
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Reconstitution assays: Incorporating purified atpB into proteoliposomes with other F0 subunits to assess proton conductance capabilities.
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Complex assembly studies: Using analytical ultracentrifugation or native gel electrophoresis to evaluate the ability of recombinant atpB to associate with other ATP synthase subunits.
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Complementation experiments: Testing whether the recombinant protein can restore function in B. subtilis atp mutants that show decreased growth yield (43-56% of wild-type) and growth rate (61-66% of wild-type) .
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Proton translocation measurements: Using pH-sensitive fluorescent dyes to monitor proton movement across reconstituted membranes containing atpB.
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Structural integrity verification: Employing circular dichroism spectroscopy to confirm proper protein folding and secondary structure elements essential for function.
How do mutations in the atpB gene affect B. subtilis physiology and metabolism?
Deletion studies of the atp operon, which includes atpB, reveal profound effects on B. subtilis physiology and metabolism, demonstrating the central role of ATP synthase in cellular energetics.
Table 2: Physiological effects of ATP synthase mutations in B. subtilis
| Parameter | Wild-type | atp Mutant 1 | atp Mutant 2 |
|---|---|---|---|
| Growth on succinate | Normal | Unable | Unable |
| Growth yield (% of WT) | 100% | 43% | 56% |
| Growth rate (% of WT) | 100% | 61% | 66% |
| Intracellular ATP/ADP ratio | Normal | ~50% decrease | ~50% decrease |
| By-product formation | Normal | ~2-fold increase | ~2-fold increase |
| Primary metabolic by-product | Various | Acetate | Acetate |
| Glycolysis turnover | Normal | Increased | Increased |
| Respiration rate | Normal | Stimulated | Stimulated |
| Expression of respiratory enzymes | Baseline | Increased | Increased |
This comprehensive metabolic reprogramming demonstrates how B. subtilis compensates for ATP synthase deficiency by increasing substrate-level phosphorylation, primarily through enhanced glycolysis and acetate production . The increased glycolysis turnover leads to higher NADH synthesis, explaining the stimulated respiration rate and upregulation of respiratory enzyme genes .
What role does ATP synthase play during B. subtilis sporulation and germination?
ATP synthase likely plays a crucial role in the energy-intensive processes of B. subtilis sporulation and germination. Proteome analysis of germinating and outgrowing B. subtilis has identified 2,191 proteins across 14 time points (0-130 minutes post-germination), which were categorized into distinct expression clusters .
When designing experiments to investigate ATP synthase function during these developmental transitions, researchers should consider:
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Temporal expression analysis: Monitoring atpB expression levels throughout the germination and outgrowth timeline using quantitative proteomics .
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Cluster analysis: Determining whether atpB expression correlates with other energy metabolism proteins during germination to identify potential co-regulated networks .
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Functional studies: Comparing germination efficiency and outgrowth kinetics between wild-type and ATP synthase-deficient strains to quantify the energetic requirements during these transitions.
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In situ activity measurements: Developing assays to measure ATP synthesis rates during specific stages of germination and outgrowth.
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Conditional knockdowns: Creating inducible atpB depletion strains to investigate the timing of ATP synthase requirement during developmental transitions.
How can researchers design experiments to study interactions between atpB and other ATP synthase subunits?
Understanding subunit interactions is crucial for elucidating ATP synthase assembly and function. The following experimental approaches are recommended:
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Cross-linking coupled with mass spectrometry: This technique can identify interaction interfaces between atpB and other subunits within the assembled complex.
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Co-immunoprecipitation studies: Using antibodies against atpB or other ATP synthase subunits to pull down interaction partners and confirm associations .
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FRET-based interaction assays: Tagging atpB and potential interaction partners with fluorescent proteins to monitor proximity in living cells.
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Bacterial two-hybrid screening: Systematic testing of binary interactions between atpB and other ATP synthase subunits.
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Mutagenesis analysis: Creating targeted mutations in potential interaction domains of atpB to disrupt specific subunit contacts and assess functional consequences.
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Complementation assays: Testing whether co-expression of atpB with other F0 subunits can restore function in corresponding deletion mutants.
How can optogenetic tools be applied to study atpB expression and function?
Recent advances in optogenetic control of B. subtilis gene expression provide powerful tools for studying atpB regulation and function with unprecedented temporal precision .
Table 3: Optogenetic system parameters for B. subtilis gene expression control
| Parameter | Specifications |
|---|---|
| Light-responsive system | CcaSR two-component system |
| Light control mechanism | Green/red photoreversible |
| Required chromophore | Phycocyanobilin (PCB) |
| Dynamic range | >70-fold activation |
| Response characteristics | Rapid dynamics |
| PCB production enhancement | Translational fusion of biosynthetic enzymes |
| Expression control | Engineered chimeric promoter |
| Photosensor optimization | Miniaturized photosensor kinase |
Researchers can apply this system to atpB studies by:
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Temporal expression control: Placing atpB under optogenetic control to precisely regulate its expression during specific growth phases or stress conditions .
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Dose-response analysis: Correlating different light intensities with atpB expression levels and corresponding ATP synthesis rates.
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Spatial patterning: Creating intracellular gradients of atpB expression to study localized effects on energy metabolism.
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Pulse-chase experiments: Using brief pulses of activating light to induce atpB expression, followed by protein tracking to determine turnover rates.
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Coordination studies: Simultaneously controlling multiple ATP synthase subunits with different optogenetic systems to investigate assembly dynamics .
What are the methodological considerations for generating and validating antibodies against B. subtilis atpB?
Developing specific antibodies against membrane proteins like atpB presents unique challenges. Based on current antibody production methodologies, researchers should consider:
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Antigen design strategy: Using recombinant full-length atpB protein with His-tag or synthesizing peptides corresponding to hydrophilic regions of the protein.
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Antibody format selection: Both monoclonal and polyclonal antibodies have been successfully developed against ATP synthase subunits, each with different advantages for specific applications.
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Validation protocols: Comprehensive validation using multiple techniques:
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Application optimization: For immunofluorescence applications, cells should be fixed in 4% paraformaldehyde for 10 minutes at 37°C, permeabilized with 0.05% Triton X-100 in PBS for 20 minutes, and blocked with 2% negative serum for 30 minutes at room temperature .
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Epitope mapping: Determining which regions of atpB are recognized by the antibody to understand potential limitations in detecting native versus denatured protein.
How can researchers analyze ATP synthase dynamics during stress responses in B. subtilis?
Understanding how ATP synthase responds to environmental stress provides insights into bacterial adaptation mechanisms. Methodological approaches include:
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Stress condition optimization: Exposing B. subtilis cultures to precisely controlled stressors (nutrient limitation, oxidative stress, antibiotics) that affect energy metabolism.
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Time-course expression analysis: Monitoring atpB expression levels during stress adaptation using quantitative proteomics or RNA-seq, similar to approaches used in germination studies .
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Functional measurements: Quantifying ATP synthesis rates under different stress conditions using luciferase-based ATP assays.
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Subcellular localization studies: Using immunofluorescence or fluorescent protein fusions to track potential redistribution of ATP synthase during stress responses.
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Genetic interaction mapping: Performing synthetic genetic array analysis to identify genes that become essential specifically in ATP synthase-deficient backgrounds under stress conditions.
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Metabolic flux analysis: Measuring changes in carbon flux through central metabolism in wild-type versus ATP synthase mutants during stress adaptation, building on observations of increased acetate production in ATP synthase-deficient cells .
