Recombinant Ralstonia pickettii ATP synthase subunit b (atpF)

What is Ralstonia pickettii ATP synthase subunit b (atpF) and what are its structural features?

Ralstonia pickettii ATP synthase subunit b (atpF) is a component of the F-type ATP synthase complex, specifically part of the F₀ sector. It is also known by alternative names including ATP synthase F(0) sector subunit b, ATPase subunit I, and F-type ATPase subunit b. The protein is encoded by the atpF gene and has been identified in Ralstonia pickettii strain 12J with a corresponding UniProt accession number B2UGV3 .

Structurally, this protein functions as part of the membrane-embedded portion of the ATP synthase complex, which is responsible for facilitating proton transport across the membrane. The b subunit typically forms a dimeric peripheral stalk that connects the F₁ and F₀ sectors of the ATP synthase complex, providing structural stability during the rotational catalysis mechanism.

How does ATP synthase subunit b contribute to energy metabolism in Ralstonia pickettii?

In R. pickettii, as in other bacteria, ATP synthase subunit b serves as a critical structural component that links the membrane-embedded F₀ portion with the catalytic F₁ portion of the ATP synthase complex. This linkage is essential for the conversion of the proton gradient energy into ATP synthesis.

From a functional perspective, the b subunit:

• Forms part of the stator that prevents rotation of the F₁ sector during ATP synthesis

• Helps maintain the structural integrity of the ATP synthase complex

• Contributes to the efficient coupling of proton translocation to ATP synthesis

These functions are crucial for cellular energy metabolism, particularly in bacteria like R. pickettii that need to adapt to various environmental conditions.

What are the optimal storage conditions for recombinant R. pickettii ATP synthase subunit b?

The shelf life and stability of recombinant R. pickettii ATP synthase subunit b depend on multiple factors including storage state, buffer ingredients, and storage temperature. According to product information, the following guidelines are recommended:

Repeated freezing and thawing significantly reduces protein stability and should be avoided. For short-term use, working aliquots can be stored at 4°C for up to one week . To maximize stability, it is advisable to prepare small aliquots after reconstitution to minimize freeze-thaw cycles.

What is the recommended protocol for reconstitution of lyophilized R. pickettii ATP synthase subunit b?

For optimal reconstitution of lyophilized recombinant R. pickettii ATP synthase subunit b, the following methodology is recommended:

• Briefly centrifuge the vial prior to opening to bring contents to the bottom

• Reconstitute the protein in deionized sterile water to achieve a concentration of 0.1-1.0 mg/mL

• Add glycerol to a final concentration of 5-50% (with 50% being the default recommendation)

• Prepare multiple small-volume aliquots

• Store reconstituted aliquots at -20°C/-80°C for long-term storage

This methodological approach helps maintain protein stability and activity while minimizing degradation during storage. The addition of glycerol serves as a cryoprotectant that prevents protein denaturation during freeze-thaw cycles.

What analytical techniques are most effective for verifying the purity and integrity of recombinant R. pickettii ATP synthase subunit b?

Multiple analytical techniques can be employed to verify the purity and integrity of recombinant R. pickettii ATP synthase subunit b:

• SDS-PAGE Analysis: This is the primary method used to assess protein purity, with commercial preparations typically showing >85% purity . The technique separates proteins based on molecular weight, allowing visualization of the target protein band and potential contaminants.

• Western Blotting: For immunological verification of protein identity, western blotting using antibodies specific to ATP synthase subunit b or to any fusion tags present can provide confirmation.

• Mass Spectrometry: For detailed characterization, mass spectrometry techniques such as MALDI-TOF or LC-MS/MS can verify the exact molecular weight and amino acid sequence.

• Functional Assays: Depending on the research objectives, functional assays examining ATP hydrolysis or synthesis may provide evidence of proper folding and activity.

• Circular Dichroism: This technique can be used to assess the secondary structure of the protein, providing information about proper folding.

When reporting purity assessments, researchers should include methodology details and representative images of gels to support claims of protein quality.

How can recombinant R. pickettii ATP synthase subunit b be used in studies of bacterial bioenergetics?

Recombinant R. pickettii ATP synthase subunit b serves as a valuable tool for investigating bacterial bioenergetics through several experimental approaches:

• Structural Studies: The purified protein can be used for crystallography or cryo-EM studies to elucidate the structural organization of bacterial ATP synthases, particularly focusing on the arrangement of the stator complex.

• Protein-Protein Interaction Analysis: Techniques such as co-immunoprecipitation, crosslinking studies, or yeast two-hybrid assays can help identify interaction partners within the ATP synthase complex or with other cellular components.

• Mutational Analysis: Site-directed mutagenesis of key residues can provide insights into structure-function relationships, similar to studies performed with other ATP synthase components in related Ralstonia species where phosphorylation of key residues affected enzyme activity .

• Comparative Bioenergetics: Comparing ATP synthase components across different bacterial species can reveal adaptations to specific environmental niches or energy requirements.

• Inhibitor Studies: Using the recombinant protein to screen for specific inhibitors could lead to the development of targeted antimicrobials, particularly relevant given the emerging pathogenicity of R. pickettii.

What potential post-translational modifications might affect R. pickettii ATP synthase subunit b function?

Post-translational modifications (PTMs) can significantly impact protein function, and while specific information about PTMs in R. pickettii ATP synthase subunit b is limited in the provided search results, insights can be drawn from related bacterial ATP synthase components:

Studies with Ralstonia eutropha, a related species, have demonstrated that phosphorylation plays a significant role in regulating ATP synthase components. For instance, phosphorylation of Thr373 in PHB synthase PhaC1 was found to be growth phase-dependent, occurring in the stationary phase but not in exponential or PHB accumulation phases . Similarly, Ser35 of PHB depolymerase PhaZa1 was identified in phosphorylated form in both exponential and stationary growth phases.

This suggests that ATP synthase subunit b in R. pickettii might also be subject to phosphorylation events that could regulate its activity depending on cellular energy demands or environmental conditions. Potential methodological approaches to investigate this include:

• Phosphoproteomic analysis using mass spectrometry

• Site-directed mutagenesis of potential phosphorylation sites

• In vitro phosphorylation assays using bacterial kinases

• Functional assays comparing wild-type and phosphomimetic variants

How does the genetic diversity of clinical R. pickettii isolates impact ATP synthase structure and function?

Genetic diversity among clinical isolates of R. pickettii has been documented through multilocus sequence typing (MLST) studies, which identified multiple sequence types (STs) among clinical isolates, with ST9 being the most prevalent . This genetic diversity may extend to ATP synthase components, including the atpF gene encoding subunit b.

Methodological considerations for investigating the impact of genetic diversity on ATP synthase include:

• Comparative Genomic Analysis: Sequencing the atpF gene from multiple clinical isolates can reveal polymorphisms that might affect protein structure or function.

• Protein Expression Profiling: Quantitative proteomics approaches can determine whether expression levels of ATP synthase components vary among different strain types.

• Functional Assays: Comparing ATP synthesis rates or proton pumping efficiency among different clinical isolates could reveal functional consequences of genetic variations.

• Antibiotic Susceptibility Testing: Since ATP synthase is a potential target for antibacterial compounds, variations in the complex might contribute to differences in antibiotic susceptibility profiles observed among clinical isolates .

• Structure Prediction: Computational modeling of variant proteins can predict how amino acid substitutions might alter protein-protein interactions within the ATP synthase complex.

What are the most reliable methods for accurate identification of R. pickettii in research settings?

Accurate identification of R. pickettii is crucial for research validity. Several complementary methods have been evaluated for their reliability:

• Specific PCR: A specific primer targeting R. pickettii produces a characteristic 210 bp amplicon. The PCR protocol involves initial denaturation at 95°C for 5 minutes, followed by 30 cycles of 94°C for 40s, 55°C for 40s, and 72°C for 1 min, with a final extension at 72°C for 5 min .

• 16S rDNA Sequencing: This method provides reliable species-level identification based on the highly conserved 16S ribosomal RNA gene sequence.

• VITEK 2 System: This automated microbial identification system has been used for R. pickettii identification, though comparison studies suggest it may occasionally misidentify closely related Ralstonia species .

A comparative analysis of these methods demonstrated that while the VITEK 2 system identified all 48 strains in one study as R. pickettii, specific PCR and 16S rDNA experiments confirmed only 30 and 34 strains, respectively, as R. pickettii . This highlights the importance of using multiple identification methods, particularly molecular techniques, when working with this organism.

What experimental controls are essential when studying recombinant R. pickettii ATP synthase components?

When conducting research with recombinant R. pickettii ATP synthase components such as subunit b (atpF), several critical experimental controls should be implemented:

• Expression System Controls:

  • Empty vector control to account for background from the expression system

  • Known recombinant protein expressed in the same system (E. coli or Baculovirus) for comparison

• Protein Quality Controls:

  • SDS-PAGE analysis to verify protein size and purity (>85% purity is standard for commercial preparations)

  • Western blot with tag-specific antibodies if the recombinant protein contains affinity tags

• Functional Controls:

  • Heat-inactivated protein sample to establish baseline in activity assays

  • Protease inhibitor treatments to assess the contribution of contaminating proteases to any observed effects

• Specificity Controls:

  • Comparison with related proteins (e.g., ATP synthase subunits from other Ralstonia species)

  • Inclusion of known interacting partners versus non-interacting proteins in binding studies

• Storage Stability Controls:

  • Comparison of freshly prepared versus stored protein samples

  • Assessment of protein functionality after different storage conditions

How might ATP synthase components contribute to R. pickettii pathogenicity and virulence?

While direct evidence linking ATP synthase components to R. pickettii pathogenicity is limited in the provided search results, several indirect connections can be hypothesized based on the organism's characteristics as an opportunistic pathogen:

R. pickettii is known to cause infections particularly in immunocompromised hosts, with documented cases of bacteremia . The pathogen produces an extracellular protease, RpA, which is required for its pathogenicity to mammalian cell lines . ATP synthase, as the primary energy-generating system, likely plays a supportive role in pathogenicity by:

• Energy Provision: Supporting the expression and secretion of virulence factors such as the RpA protease

• Adaptation to Host Environments: ATP synthase efficiency may contribute to the ability of R. pickettii to survive in different host microenvironments with varying pH and nutrient availability

• Stress Response: Efficient energy metabolism is crucial for bacterial stress responses during host immune attacks

• Biofilm Formation: ATP production supports the metabolic demands of biofilm production, which can enhance antimicrobial resistance

• Persistence: Adequate energy production is necessary for bacterial persistence during chronic infection

Future research directions might include investigating whether ATP synthase inhibitors affect the expression or activity of known virulence factors like RpA protease, or whether mutations in ATP synthase genes correlate with changes in virulence in animal models such as the immunodeficient mice that developed ataxia when infected with R. pickettii .

What methodological approaches are most effective for studying the role of energy metabolism in R. pickettii infections?

To investigate the role of energy metabolism, particularly involving ATP synthase, in R. pickettii infections, researchers can employ several methodological approaches:

• Gene Expression Analysis:

  • RT-qPCR to measure expression of ATP synthase genes during different infection stages

  • RNA-seq to identify co-regulated pathways during host adaptation

• Genetic Manipulation:

  • Construction of atpF knockdown or knockout mutants to assess effects on virulence

  • Site-directed mutagenesis of key residues to create strains with altered ATP synthase efficiency

• Infection Models:

  • Immunodeficient mouse models can be particularly useful as they have demonstrated susceptibility to R. pickettii, developing characteristic ataxia syndromes

  • Cell culture models using human cell lines relevant to clinical infections

• Metabolic Analysis:

  • Measurement of ATP production in wild-type versus mutant strains

  • Metabolomic profiling under different infection-relevant conditions

• Visualization Techniques:

  • GFP-expressing constructs (similar to those developed for related Ralstonia species) to track bacterial localization during infection

  • Fluorescent probes to assess membrane potential as an indicator of ATP synthase function

• Clinical Correlations:

  • Analysis of ATP synthase gene sequences in clinical isolates with different virulence profiles

  • Correlation of energy metabolism markers with clinical outcomes in patient samples