Recombinant Delftia acidovorans ATP synthase subunit b (atpF)

What is the Delftia acidovorans ATP synthase subunit b (atpF) protein?

The ATP synthase subunit b (atpF) from Delftia acidovorans is a component of the F0 sector of the F-type ATP synthase complex, which is essential for cellular energy production through oxidative phosphorylation. This protein functions as part of the membrane-embedded portion of ATP synthase, specifically serving as a peripheral stalk that connects the F1 and F0 domains. The recombinant form (UniProt number A9BPU3) is derived from the strain DSM 14801 / SPH-1, with the protein encoding gene designated as atpF (locus name Daci_0416). It possesses a full amino acid sequence of 156 amino acids with characteristic hydrophobic and hydrophilic regions that facilitate its function in the ATP synthase complex .

What are the basic structural characteristics of recombinant Delftia acidovorans ATP synthase subunit b?

The recombinant D. acidovorans ATP synthase subunit b has a complete amino acid sequence of: MSINATLFVQAIVFLILVLFTMKFVWPPIAKALDERALKIADGLAAADKAKTDLAAANKRVEQELAQTRNETASRLADAERRAQAIIEEAKARASEEGNKIVAAARAEAEQQTVQAREALREQVAALAVKGAEQILRKEVDAGVHADLLNRLKTEL. Structural analysis reveals a hydrophobic N-terminal region (approximately the first 24 residues) that likely embeds in the membrane, followed by a predominantly hydrophilic region that extends into the cytoplasm. This architecture is consistent with its function as a peripheral stalk in the ATP synthase complex. The protein typically forms homodimers that contribute to the stability of the ATP synthase complex by connecting the membrane-embedded F0 sector with the catalytic F1 portion .

What is the biological significance of Delftia acidovorans in microbial communities?

Delftia acidovorans has emerged as a significant organism in diverse microbial communities with multifaceted ecological roles. It has been identified as a component of the human skin microbiome, where it secretes substances that selectively inhibit the growth of Staphylococcus epidermidis through triggering reactive oxygen species (ROS) production via the tricarboxylic acid (TCA) cycle. This selective antimicrobial activity may contribute to microbial community structure and balance on the skin. Interestingly, while it inhibits S. epidermidis growth, it does not affect Staphylococcus aureus, suggesting sophisticated mechanisms for interspecies competition. The skin microbiome balance between these organisms has implications for dermatological health, as altered ratios between S. epidermidis and S. aureus are associated with skin disorders including atopic dermatitis .

How should recombinant Delftia acidovorans ATP synthase subunit b be stored and handled for optimal stability?

For optimal stability of recombinant D. acidovorans ATP synthase subunit b, the following storage and handling protocols are recommended:

• Store the protein at -20°C for regular use

• For extended storage periods, conserve at either -20°C or -80°C

• Avoid repeated freezing and thawing cycles, as this significantly reduces protein stability and activity

• Prepare working aliquots and store them at 4°C for up to one week to minimize freeze-thaw cycles

• The protein is typically supplied in a Tris-based buffer containing 50% glycerol that has been optimized for maintaining structural integrity

These recommendations are based on experimental stability studies and are essential for maintaining the functional and structural integrity of the protein for research applications .

How does the ATP synthase subunit b from Delftia acidovorans compare structurally and functionally with homologous proteins from other bacterial species?

The functional comparison of D. acidovorans ATP synthase subunit b with other bacterial homologs indicates similar roles in maintaining ATP synthase structural integrity, but with potential differences in regulatory mechanisms. Unlike some well-characterized systems like E. coli, where extensive mutagenesis studies have mapped critical functional residues, the D. acidovorans protein has fewer published studies examining structure-function relationships. Preliminary analyses suggest that the peripheral stalk in D. acidovorans may contain specific adaptations related to environmental stress response, possibly reflecting the organism's ecological niche as both a soil inhabitant and skin commensal .

What are the implications of Delftia acidovorans antimicrobial activities for skin microbiome research?

The discovery that D. acidovorans secretes substances that selectively inhibit S. epidermidis growth through TCA cycle-triggered ROS production presents significant implications for skin microbiome research:

• Microbial Community Regulation: D. acidovorans appears to play a role in shaping microbial community composition through selective antimicrobial activity, creating microenvironments that favor certain species over others.

• Pathophysiological Relevance: The selective inhibition of S. epidermidis without affecting S. aureus may contribute to dysbiosis associated with skin conditions. Since S. epidermidis typically helps control S. aureus populations, D. acidovorans overgrowth could potentially disrupt this balance.

• Therapeutic Potential: Understanding the mechanisms of this selective antimicrobial activity could lead to novel antimicrobial strategies that target specific pathogens while preserving beneficial commensals.

• Biomarker Development: Changes in D. acidovorans population dynamics could potentially serve as biomarkers for skin microbiome imbalances associated with various dermatological conditions.

These findings suggest a complex role for D. acidovorans in skin health that warrants further investigation, particularly in the context of inflammatory skin diseases where microbiome dysbiosis is implicated .

What potential role might the ATP synthase complex play in Delftia acidovorans' environmental adaptability?

The ATP synthase complex, including the subunit b (atpF), likely contributes significantly to D. acidovorans' remarkable environmental adaptability across diverse niches from soil to human skin. Several hypotheses can be proposed based on current research:

• Metabolic Flexibility: The ATP synthase complex may possess regulatory adaptations that optimize energy production under varying nutrient conditions, supporting D. acidovorans' ability to utilize diverse carbon and phosphorus sources.

• pH Tolerance: Given D. acidovorans' presence in acidic environments (as suggested by its name), its ATP synthase complex might incorporate structural adaptations for maintaining proton gradient efficiency at lower pH values compared to neutralophilic bacteria.

• Stress Response Integration: The ATP synthase complex could be integrated with stress response pathways, allowing rapid modulation of energy production during environmental transitions or stresses.

• Xenobiotic Metabolism Support: The efficient energy production facilitated by optimized ATP synthase function may support the energetically demanding xenobiotic degradation pathways for which D. acidovorans is known, including its ability to degrade organofluorine compounds.

Research examining ATP synthase gene expression patterns under different environmental conditions could provide insights into these adaptive mechanisms .

How might the dehalogenase activities of Delftia acidovorans interact with its energy metabolism pathways?

The documented dehalogenase activities of D. acidovorans, particularly its ability to degrade perfluorochemicals (PFCs) and other organofluorine compounds, likely interact with energy metabolism pathways in several significant ways:

• Energetic Coupling: Dehalogenation reactions may be coupled to energy-generating pathways, potentially utilizing ATP produced by the ATP synthase complex to drive energetically unfavorable steps in dehalogenation.

• Regulatory Coordination: Expression of dehalogenase enzymes and ATP synthase components may be co-regulated to balance energy production with xenobiotic degradation capabilities.

• Electron Transport Integration: Some dehalogenation reactions may interface with respiratory electron transport chains, potentially sharing electron carriers or redox components with pathways that ultimately drive ATP synthesis.

• Adaptation Signatures: Comparative genomic analysis between strain D4B (isolated from PFAS-contaminated soil) and other D. acidovorans strains might reveal co-evolutionary adaptations in both dehalogenase genes and energy metabolism genes, including ATP synthase components.

This interaction represents an interesting area for future research, particularly in the context of developing bioremediation strategies for persistent organic pollutants .

What are the optimal expression and purification protocols for recombinant Delftia acidovorans ATP synthase subunit b?

Based on published methodologies for similar proteins, the following optimized protocol is recommended for expression and purification of recombinant D. acidovorans ATP synthase subunit b:

Expression System Selection:

• E. coli BL21(DE3) is recommended as the primary expression host due to its high expression levels and compatibility with membrane proteins

• For difficult-to-express constructs, consider C41(DE3) or C43(DE3) strains specifically engineered for membrane protein expression

Expression Vector Design:

• Include a C-terminal hexahistidine or Strep-tag for purification

• Consider using a vector with tightly controlled induction (e.g., pET system)

• Optimize codon usage for E. coli if necessary

Expression Conditions:

• Culture growth at 37°C to OD600 of 0.6-0.8

• Temperature reduction to 18-20°C prior to induction

• Induction with 0.1-0.5 mM IPTG

• Extended expression period (16-20 hours) at the reduced temperature

Purification Protocol:

• Cell lysis in buffer containing 50 mM Tris-HCl pH 8.0, 300 mM NaCl, 10% glycerol, and protease inhibitors

• Membrane fraction isolation by ultracentrifugation (100,000 × g, 1 hour)

• Membrane protein solubilization with 1% n-dodecyl-β-D-maltoside (DDM) or 1% n-octyl-β-D-glucopyranoside (OG)

• Affinity chromatography using Ni-NTA or Strep-Tactin resin

• Size exclusion chromatography for final polishing

This methodology has been adapted from successful approaches used for other ATP synthase components and should be optimized for specific research requirements .

What assays can be used to evaluate the functional activity of recombinant Delftia acidovorans ATP synthase subunit b?

While the ATP synthase subunit b does not possess catalytic activity independently, several approaches can be used to assess its functional integrity and interactions:

Structural Integrity Assays:

• Circular Dichroism (CD) Spectroscopy: To confirm proper secondary structure formation, particularly the predicted alpha-helical content

• Thermal Shift Assays: To assess protein stability under varying conditions

• Size Exclusion Chromatography with Multi-Angle Light Scattering (SEC-MALS): To confirm proper oligomeric state (typically dimeric)

Functional Interaction Assays:

• Pull-down Assays: Using tagged recombinant subunit b to identify binding partners from the ATP synthase complex

• Surface Plasmon Resonance (SPR) or Isothermal Titration Calorimetry (ITC): To quantify binding affinities with other ATP synthase subunits

• Reconstitution Assays: Incorporation of recombinant subunit b into liposomes with other ATP synthase components to assess functional complementation

Structural Studies:

• X-ray Crystallography: To determine high-resolution structure, potentially in complex with interaction partners

• Cryo-electron Microscopy: For visualization of subunit b in the context of the entire ATP synthase complex

These approaches collectively provide a comprehensive assessment of the recombinant protein's structural integrity and capacity to engage in native interactions .

How can researchers effectively study the interaction between Delftia acidovorans ATP synthase and its role in antimicrobial compound production?

To investigate the potential relationship between D. acidovorans ATP synthase and its antimicrobial activities, the following integrated research approach is recommended:

Genetic Manipulation Strategy:

• Generate atpF gene knockout or knockdown strains using CRISPR-Cas9 or antisense RNA approaches

• Create point mutations in conserved residues of atpF to create partially functional variants

• Develop an inducible expression system for controlled atpF expression levels

Functional Assessment:

• Compare antimicrobial compound production between wild-type and atpF-modified strains

• Measure ATP production capacity across strains with varying atpF functionality

• Assess growth kinetics under different metabolic conditions to determine energy requirements for antimicrobial production

Metabolomic Analysis:

• Use untargeted metabolomics to identify differences in metabolite profiles between wild-type and atpF-modified strains

• Employ stable isotope labeling to trace carbon flux through central metabolism to antimicrobial compound synthesis

• Quantify changes in TCA cycle intermediates that might influence ROS production

Transcriptomic Integration:

• Perform RNA-Seq analysis to identify gene expression changes in biosynthetic pathways when atpF function is altered

• Map regulatory networks connecting energy metabolism to antimicrobial compound production

This multidisciplinary approach would help establish whether ATP synthase function directly influences antimicrobial capabilities or whether these are independently regulated processes in D. acidovorans .

What considerations should be made when designing experiments to study the role of ATP synthase in Delftia acidovorans' dehalogenase activities?

When investigating potential relationships between ATP synthase function and dehalogenase activities in D. acidovorans, researchers should consider the following experimental design elements:

Energy Dependence Assessment:

• Compare dehalogenase activity in the presence of ATP synthase inhibitors (e.g., DCCD, oligomycin) at concentrations that partially inhibit ATP production

• Measure ATP consumption during dehalogenation reactions using luciferase-based assays

• Determine whether ATP or other high-energy phosphate compounds directly participate in the dehalogenation reaction mechanism

Genetic Manipulation Approaches:

• Generate conditional atpF mutants to allow controlled reduction in ATP synthase activity

• Create reporter constructs linking dehalogenase gene promoters to fluorescent proteins to monitor expression changes when ATP synthase function is altered

• Perform complementation studies with atpF variants having different efficiencies

Physiological Context Considerations:

• Evaluate dehalogenase activity under different growth conditions that affect energy status (carbon limitation, oxygen limitation)

• Determine whether dehalogenase induction affects ATP synthase gene expression through transcriptomic analysis

• Compare wild-type and atpF-modified strains for growth on halogenated compounds as sole carbon sources

Biochemical Analysis:

• Purify the ATP synthase complex and dehalogenase enzymes to test for direct physical interactions

• Identify potential protein-protein interaction networks using techniques like bacterial two-hybrid systems or co-immunoprecipitation

• Develop in vitro reconstitution systems to test functional coupling between energy production and dehalogenation

This systematic approach would help determine whether there are direct functional links between ATP synthesis and dehalogenation processes in D. acidovorans .

Table 1: Key Properties of Recombinant Delftia acidovorans ATP synthase subunit b (atpF)

Table 2: Comparative Analysis of Delftia acidovorans Antimicrobial Effects on Skin Bacteria