Recombinant Yersinia pestis bv. Antiqua ATP synthase subunit b (atpF)

What expression systems are optimal for producing recombinant Y. pestis ATP synthase subunit b?

Several expression systems have proven effective for producing recombinant Y. pestis proteins, including ATP synthase components:

A plant-based transient expression system using deconstructed tobacco mosaic virus (TMV) replicons has demonstrated exceptional yields (1-2 mg/g of fresh leaf weight) for recombinant Y. pestis proteins . This approach allows rapid testing of different targeting signals and fusion partners.

For atpF specifically, recombinant protein production in E. coli with an N-terminal His-tag has been successfully employed for the homologous protein from Y. pseudotuberculosis , suggesting a similar approach would work for Y. pestis atpF.

What purification and characterization methods are most effective for recombinant Y. pestis atpF?

Established purification protocols for recombinant Y. pestis atpF include:

• Initial purification:

  • Ammonium sulfate fractionation (30-60% saturation)

  • FPLC Superose gel filtration chromatography

• Affinity purification:

  • Immobilized metal affinity chromatography (IMAC) for His-tagged proteins

  • GST-based purification for GST fusion proteins

• Characterization methods:

  • SDS-PAGE for purity assessment (>85% purity typically achieved)

  • Circular dichroism (CD) spectroscopy for secondary structure analysis

  • Size exclusion chromatography to determine oligomeric state

  • Mass spectrometry for precise molecular mass determination

Researchers should consider that membrane proteins like atpF may require detergents for solubilization and stability throughout purification. Commonly used detergents include n-dodecyl-β-D-maltoside (DDM) or n-octyl-β-D-glucopyranoside (OG).

What are the recommended storage conditions for maintaining stability of recombinant Y. pestis atpF?

Based on established protocols for similar recombinant proteins:

Best practices include:

• Storage in Tris-based buffer with 50% glycerol to prevent freezing damage

• Avoiding repeated freeze-thaw cycles

• Storing working aliquots at 4°C for up to one week

• For extended storage, maintaining samples at -80°C

The shelf life of atpF preparations depends on multiple factors including buffer composition, storage temperature, and the intrinsic stability of the protein itself .

What methodologies are most effective for studying the role of atpF in Y. pestis pathogenesis?

Several complementary approaches have proven valuable:

• Genetic manipulation techniques:

  • Gene deletion using lambda Red recombineering or CRISPR-Cas9

  • Conditional expression systems (inducible promoters)

  • Site-directed mutagenesis for structure-function analysis

• In vitro assays:

  • ATP synthesis/hydrolysis activity measurements

  • Membrane potential assessments using fluorescent probes

  • Growth under varying pH, temperature, and nutrient conditions

• Infection models:

  • Macrophage cell culture systems (measuring bacterial survival)

  • Neutrophil killing assays (monitoring resistance to antimicrobial peptides)

  • Mouse models of bubonic and pneumonic plague

• Structural techniques:

  • X-ray crystallography or cryo-EM to determine protein structure

  • Hydrogen-deuterium exchange mass spectrometry for conformational dynamics

  • Molecular dynamics simulations to predict functional interactions

A particularly informative approach combines deletion mutants with in vivo infection models to assess the impact on virulence, bacterial burden, and host immune response .

How do ATP synthase inhibitors affect Y. pestis survival and virulence, and what are the implications for therapeutic development?

ATP synthase represents a potential drug target for anti-Y. pestis therapy, particularly given the emergence of antibiotic-resistant strains . Research on ATP synthase inhibitors has revealed:

• Effect on bacterial physiology:

  • Disruption of energy metabolism

  • Altered membrane potential

  • Compromised pH homeostasis

  • Reduced virulence factor expression and secretion

• Experimental approaches for studying inhibitors:

  • In vitro ATP synthesis assays using purified proteins

  • Bacterial growth inhibition assays

  • Combination therapy with existing antibiotics

  • Structure-based drug design targeting conserved regions

• Candidate inhibitor classes:

  • Diarylquinolines (similar to bedaquiline used against M. tuberculosis)

  • Small molecule ATPase inhibitors (similar to those identified for YscN, the T3SS ATPase)

  • Peptide-based inhibitors targeting subunit interfaces

While specific data on atpF-targeted inhibitors in Y. pestis is limited, research on the homologous T3SS ATPase (YscN) has identified small molecule inhibitors with IC50 values below 20 μM that prevent secretion of virulence factors . This suggests similar approaches could be applied to ATP synthase components.

How does the conservation of atpF across Y. pestis strains impact its potential as a diagnostic or therapeutic target?

Analysis of atpF conservation reveals important insights for research applications:

The high conservation of atpF across Y. pestis strains makes it a potentially valuable target for:

• Diagnostic applications:

  • Development of antibody-based detection methods

  • PCR-based identification targeting conserved regions

  • Mass spectrometry-based bacterial identification

• Therapeutic approaches:

  • Inhibitors targeting conserved catalytic sites

  • Vaccines incorporating conserved epitopes

  • Antibody-based therapies

• Evolutionary studies:

  • Analyzing microevolution among Y. pestis lineages

  • Comparing with homologs in Y. pseudotuberculosis to understand pathogen evolution

The high sequence similarity (>99%) between atpF from different Y. pestis biovars suggests that findings from one strain would likely apply to others, facilitating broader application of research results .

What are the experimental challenges in distinguishing the role of atpF in basic metabolism versus specific virulence mechanisms?

Researchers face several methodological challenges:

• Separating essential from virulence functions:

  • Complete deletion may be lethal, requiring conditional knockout systems

  • Point mutations affecting specific functions rather than complete gene deletion

  • Careful design of complementation studies with varying expression levels

• Experimental approaches to address this challenge:

  • Temperature-sensitive mutants allowing study at permissive conditions

  • Tissue-specific or time-dependent gene expression systems

  • Careful measurement of both metabolic and virulence parameters

  • Comparison with related non-pathogenic bacteria expressing the same protein

• Data integration strategies:

  • Combining transcriptomics, proteomics, and metabolomics data

  • Computational modeling of metabolic networks

  • Monitoring ATP levels and proton motive force simultaneously with virulence

Studies of Y. pestis GTPases like BipA provide a methodological template, as they demonstrated how to differentiate between metabolic and virulence phenotypes by analyzing bacterial survival in neutrophil killing assays versus growth in standard media .

How does atpF interact with other components of the ATP synthase complex, and how can these interactions be studied?

Understanding protein-protein interactions within the ATP synthase complex requires sophisticated approaches:

• Structural biology techniques:

  • Cryo-electron microscopy to visualize the entire ATP synthase complex

  • X-ray crystallography of subcomplexes

  • NMR spectroscopy for dynamic interactions

• Biochemical methods:

  • Co-immunoprecipitation with tagged components

  • Cross-linking mass spectrometry to identify interaction surfaces

  • Surface plasmon resonance to measure binding kinetics

  • Isothermal titration calorimetry for thermodynamic parameters

• Genetic approaches:

  • Bacterial two-hybrid assays

  • Suppressor mutation analysis

  • Site-directed mutagenesis of predicted interaction sites

Based on studies in related systems, atpF forms critical interactions with the a-subunit and serves as the stator connecting the F0 and F1 portions of ATP synthase . The transmembrane N-terminal domain anchors the protein in the membrane, while the C-terminal domain extends into the cytoplasm to interact with the F1 portion.

A comprehensive understanding of these interactions could lead to targeted disruption strategies with therapeutic potential against Y. pestis.