Recombinant Pseudomonas entomophila ATP synthase subunit b (atpF)

Intermediate Research Applications

• How can recombinant atpF be used to study ATP synthase inhibitors as potential antimicrobial agents?

Recombinant P. entomophila atpF can be utilized in several experimental approaches to develop and evaluate ATP synthase inhibitors:

• In vitro binding assays: Using techniques such as isothermal titration calorimetry or surface plasmon resonance to measure direct binding of inhibitor candidates to recombinant atpF .

• Reconstitution experiments: Incorporating recombinant atpF into liposomes with other ATP synthase components to create a functional model system for testing inhibitor effects on ATP synthesis rates .

• Structural studies: Employing recombinant atpF in crystallography or cryo-EM studies to determine binding sites for potential inhibitors .

• Differential scanning fluorimetry: Measuring thermal stability shifts upon inhibitor binding to identify compounds that interact with atpF .

Research has demonstrated that ATP synthase is a validated drug target for multiple pathogens. For example, bedaquiline (Sirturo) is an FDA-approved drug that targets bacterial ATP synthase and is prescribed against tuberculosis . Studies on recombinant antimicrobial peptides (defensin-d2 and actifensin) have shown that they downregulate ATP synthase F1 α subunit in Pseudomonas aeruginosa, suggesting a potential mechanism for developing new antimicrobials that could target ATP synthase in pathogenic Pseudomonas species .

• What methodologies can be used to investigate interactions between atpF and other ATP synthase subunits?

To investigate protein-protein interactions between atpF and other ATP synthase subunits, researchers can employ the following methodologies:

• Co-immunoprecipitation (Co-IP): Using antibodies against atpF to pull down interacting partners, followed by mass spectrometry identification .

• Yeast two-hybrid (Y2H): Screening for direct protein interactions between atpF and other subunits in a heterologous system .

• Bioluminescence Resonance Energy Transfer (BRET): Measuring protein interactions in living cells by tagging atpF and potential partners with appropriate fluorophores .

• Crosslinking coupled with mass spectrometry: Identifying proximity relationships between proteins within the ATP synthase complex .

• Surface Plasmon Resonance (SPR): Quantifying binding affinities and kinetics between atpF and other purified subunits .

• Hydrogen-deuterium exchange mass spectrometry (HDX-MS): Mapping interaction interfaces by measuring changes in deuterium uptake upon complex formation .

Recent studies have shown that the peripheral stalk subunits b and b′ (encoded by atpF and ATPG, respectively) are essential for chloroplast ATP synthase biogenesis, demonstrating the critical role of these interactions in the assembly and function of ATP synthase complexes across different species .

Advanced Research Applications

• How do conformational changes in ATP synthase under different pH conditions affect atpF function?

Recent research has revealed important insights into the conformational dynamics of ATP synthase under varying pH conditions, with significant implications for atpF function:

• Acidic state conformations: A 2024 study by Sharma et al. examined ATP synthase at acidic pH, revealing four distinct conformations that occur when the enzyme is exposed to an acidic environment below neutral on the pH scale. Three of these conformations represent different stages in the enzyme's reaction cycle, including two unique states not previously described .

• Structural implications for atpF: As part of the peripheral stalk, atpF must maintain structural integrity during these conformational changes. Under acidic conditions, the interactions between atpF and other subunits may be altered, affecting the stability of the entire complex .

• Methodological approaches:

  • Cryo-electron microscopy at different pH values to capture conformational ensembles

  • Molecular dynamics simulations to model pH-dependent structural changes

  • Site-directed mutagenesis of key residues in atpF that may respond to pH changes

  • FRET-based assays to measure distance changes between subunits at varying pH

• Disease relevance: Understanding these pH-dependent conformational changes is particularly important because mitochondria often become acidic in cells affected by diseases such as cancer and cardiac ischemia, as these conditions cause tissues to become oxygen-deficient or hypoxic .

The plasticity in F1-F0 coupling revealed by these studies suggests that atpF and other peripheral stalk components must be adaptable to different conformational states, highlighting their importance in maintaining ATP synthase function under various physiological conditions .

• What experimental approaches can be used to study the role of atpF in ATP synthase assembly?

Investigating the role of atpF in ATP synthase assembly requires sophisticated experimental approaches:

• Genetic manipulation techniques:

  • CRISPR-Cas9 gene editing to create knock-out or knock-down mutants of atpF

  • Transposon mutagenesis for random insertions that disrupt atpF function

  • Site-directed mutagenesis to create specific atpF variants with altered assembly properties

• Biochemical and structural techniques:

  • Blue native polyacrylamide gel electrophoresis (BN-PAGE) to visualize ATP synthase subcomplexes in various assembly states

  • Pulse-chase experiments with radioisotope labeling to track assembly kinetics

  • Immunoprecipitation using subunit-specific antibodies to isolate assembly intermediates

  • Cryo-electron microscopy to visualize assembly intermediates at high resolution

• Cellular and organellar studies:

  • Fluorescence microscopy with labeled subunits to track assembly in living cells

  • Import assays using isolated mitochondria or bacterial membrane vesicles

  • Protease protection assays to determine topology during assembly

Recent research in the green alga Chlamydomonas reinhardtii demonstrated that mutations affecting atpF (encoding subunit b) and ATPG (encoding subunit b′) completely prevented ATP synthase function and accumulation . Crossing these ATP synthase mutants with ftsh1-1 mutants (affecting the major thylakoid protease) identified AtpH as an FTSH substrate and showed that FTSH significantly contributes to the concerted accumulation of ATP synthase subunits . These findings highlight the importance of coordinated assembly and the role of quality control mechanisms in ATP synthase biogenesis.

• How can engineering of ATP synthase improve the proton-to-ATP ratio for biotechnological applications?

Recent research has demonstrated innovative approaches to engineer ATP synthase for enhanced proton-to-ATP ratio, with significant implications for biotechnology:

These engineering approaches demonstrate that ATP synthase can be modified to function efficiently at lower proton motive force conditions, enabling ATP synthesis in environments where natural ATP synthases would be ineffective .

Practical Research Methodologies

• What analytical techniques are most effective for characterizing recombinant atpF protein?

Comprehensive characterization of recombinant atpF protein requires multiple analytical techniques:

• Structural characterization:

  • Circular Dichroism (CD) spectroscopy to assess secondary structure content

  • Nuclear Magnetic Resonance (NMR) for solution structure determination

  • X-ray crystallography for high-resolution structural analysis

  • Hydrogen/Deuterium Exchange Mass Spectrometry (HDX-MS) to probe conformational dynamics

• Biochemical characterization:

  • SDS-PAGE to assess purity and apparent molecular weight (>90% purity is typically required)

  • Western blotting with anti-His antibodies to confirm tag presence

  • Size Exclusion Chromatography (SEC) to evaluate oligomeric state and homogeneity

  • Mass Spectrometry for accurate mass determination and post-translational modifications

• Functional characterization:

  • ATPase activity assays to measure enzymatic function when incorporated into the ATP synthase complex

  • Binding assays to measure interactions with other ATP synthase subunits

  • Thermal shift assays to assess protein stability

  • Reconstitution experiments in liposomes to evaluate functional integration

• Quality control metrics:

  • Endotoxin testing for research applications requiring low endotoxin levels

  • Aggregation analysis using dynamic light scattering

  • Long-term stability testing under various storage conditions

For comprehensive studies, researchers should combine multiple techniques to ensure proper characterization of both structural and functional properties of recombinant atpF protein.

• How can proteomics be used to study the effects of ATP synthase inhibitors on Pseudomonas metabolism?

Proteomic approaches offer powerful tools for investigating the effects of ATP synthase inhibitors on Pseudomonas metabolism:

• Quantitative proteomics workflow:

  • Sample preparation: Treatment of Pseudomonas cultures with ATP synthase inhibitors at different concentrations and time points

  • Protein extraction and digestion: Cell lysis followed by tryptic digestion

  • LC-MS/MS analysis: Identification and quantification of proteins

  • Bioinformatic analysis: Pathway mapping and protein-protein interaction networks

• Specific proteomic techniques:

  • Label-free quantification (LFQ) for global protein abundance changes

  • Stable Isotope Labeling with Amino acids in Cell culture (SILAC) for accurate quantification

  • Tandem Mass Tag (TMT) labeling for multiplexed analysis

  • Selected Reaction Monitoring (SRM) for targeted quantification of specific proteins

• Case study findings:
  Research on antimicrobial peptides defensin-d2 and actifensin demonstrated their ability to induce proteomic changes in Pseudomonas aeruginosa within 1 hour of treatment . The differentially expressed proteins (DEPs) were related to:

  Functional Category	Upregulated Proteins	Downregulated Proteins
  Ion transport and homeostasis	Magnesium-transporting P-type ATPase	ATP synthase F1 α subunit
  Nucleic/amino acid metabolism	Nudix hydrolase	Various metabolic enzymes
  Structural biogenesis	Bacterioferritin	Membrane-associated proteins

• Integration with other approaches:

  • Transcriptomics to correlate protein changes with gene expression

  • Metabolomics to identify altered metabolic pathways

  • Phenotypic assays to confirm functional effects (growth, motility, biofilm formation)

This multi-omics approach revealed that ATP synthase is a critical target in antimicrobial strategies against Pseudomonas species, as inhibition of the ATP synthase F1 α subunit disrupts energy metabolism and reduces pathogen viability .

Research Implications and Applications

• How does atpF contribute to the pathogenicity of Pseudomonas entomophila?

The role of atpF in Pseudomonas entomophila pathogenicity involves several key mechanisms:

• Energy provision for virulence:
  ATP synthase provides the energy necessary for various virulence mechanisms in P. entomophila, which is known to be highly pathogenic for insects, leading to rapid lethality in Drosophila melanogaster within 1-2 days of ingestion . The energy produced by ATP synthase supports:

  • Production of virulence factors

  • Motility and colonization

  • Stress responses during host invasion

  • Biofilm formation

• Integration with virulence regulation systems:

  • The GacS/GacA two-component system plays a key role in P. entomophila pathogenicity

  • Secondary metabolite production, which depends on ATP availability, controls P. entomophila virulence independently from the Gac system

  • ATP synthase activity likely influences the energy-dependent production of these virulence-associated secondary metabolites

• Response to host environment:

  • P. entomophila must adapt to changing conditions in the insect gut

  • ATP synthase function may be modulated during infection to optimize energy production

  • The peripheral stalk components like atpF are crucial for maintaining ATP synthase stability under stress conditions

• Experimental approaches to study atpF in pathogenicity:

  • Generation of atpF mutants and assessment of virulence in insect models

  • Transcriptomic and proteomic profiling of atpF expression during infection

  • Comparative studies of atpF sequence and function across Pseudomonas species with varying pathogenicity

Understanding the specific role of atpF in P. entomophila pathogenicity could lead to novel strategies for controlling this bacterial pathogen in agricultural and environmental contexts.

• What are the current challenges and future directions in ATP synthase research using recombinant subunits?

Current challenges and future directions in ATP synthase research using recombinant subunits include:

• Structural challenges:

  • Obtaining high-resolution structures of complete ATP synthase complexes with peripheral stalk components

  • Understanding dynamic conformational changes during the catalytic cycle

  • Determining the precise interactions between atpF and other subunits

• Functional reconstitution:

  • Achieving functional reconstitution of recombinant subunits into complete ATP synthase complexes

  • Developing assays to measure activity of partially assembled complexes

  • Understanding the sequential assembly process and role of each subunit

• Drug discovery applications:

  • Identifying specific inhibitors targeting peripheral stalk components like atpF

  • Developing screening assays using recombinant subunits

  • Addressing selectivity to target pathogen ATP synthases while sparing host enzymes

• Emerging methodologies:

  • Cryo-electron microscopy to capture ATP synthase in different conformational states

  • Single-molecule techniques to study rotational dynamics

  • Engineering ATP synthase with improved properties for biotechnological applications

  • Computational approaches to model subunit interactions and predict functional effects of mutations

• Therapeutic potential:

  • ATP synthase is a drug target for various infectious diseases, cardiovascular diseases, and cancer

  • Understanding how peripheral stalk components like atpF contribute to enzyme function could lead to novel therapeutic approaches

  • Development of specific inhibitors targeting bacterial ATP synthases could address antimicrobial resistance

Future research should focus on integrating structural, functional, and computational approaches to develop a comprehensive understanding of ATP synthase function and leverage this knowledge for biomedical and biotechnological applications.