Recombinant Dehalococcoides ethenogenes ATP synthase subunit b (atpF)

What is ATP synthase subunit b (atpF) in Dehalococcoides ethenogenes?

ATP synthase subunit b (atpF) is a 169-amino acid protein component of the F-type ATP synthase complex in Dehalococcoides ethenogenes. It functions as part of the F0 sector (membrane-embedded portion) of ATP synthase and plays crucial structural and functional roles in energy production. This protein is encoded by the atpF gene and has synonyms including "ATP synthase F0 sector subunit b," "ATPase subunit I," and "F-ATPase subunit b." The protein contains a hydrophobic N-terminal region that anchors it in the membrane and an extended cytoplasmic domain that contributes to the peripheral stalk of the ATP synthase complex .

How is recombinant Dehalococcoides ethenogenes atpF produced?

Recombinant production typically involves cloning the full-length atpF gene into an expression vector with an N-terminal His-tag, followed by expression in Escherichia coli. Based on available protocols, the expression system yields protein with greater than 90% purity as determined by SDS-PAGE analysis. The protein forms inclusion bodies when overexpressed in E. coli, necessitating solubilization approaches similar to those used for other ATP synthase subunits .

The general production workflow includes:

• Cloning the atpF gene into an expression vector with a His-tag

• Transformation into E. coli expression host

• Induction of protein expression

• Cell harvesting and lysis

• Protein purification using affinity chromatography

• Lyophilization to powder form for stable storage

What are the optimal storage conditions for recombinant atpF protein?

For optimal stability and activity retention, recombinant Dehalococcoides ethenogenes ATP synthase subunit b protein should be stored according to the following recommendations:

Before opening any vial containing the lyophilized protein, centrifugation is recommended to ensure the contents are at the bottom of the container .

What expression systems are most effective for producing functional recombinant atpF?

While E. coli remains the predominant expression system for recombinant Dehalococcoides ethenogenes atpF, researchers should consider several factors to optimize protein yield and functionality:

Based on experiences with similar proteins, solubilization of inclusion bodies using urea followed by stepwise dialysis in the presence of non-ionic detergents has proven effective for obtaining functional protein . For membrane proteins like atpF, the addition of stabilizing agents such as trehalose can significantly improve protein stability during purification and storage .

How can researchers effectively purify atpF for structural and functional studies?

Purification of recombinant Dehalococcoides ethenogenes atpF presents several challenges due to its membrane-associated nature. A comprehensive purification strategy should address protein solubility, stability, and conformational integrity:

• Initial solubilization approaches:

  • For inclusion bodies: Solubilization in 8M urea followed by stepwise dialysis

  • For membrane fractions: Extraction with mild detergents (DDM, LDAO)

• Affinity purification optimization:

  • For His-tagged proteins, Ni-NTA chromatography with imidazole gradient elution

  • Buffer optimization to maintain protein stability during binding and elution

• Secondary purification steps:

  • Size exclusion chromatography to remove aggregates and ensure homogeneity

  • Ion exchange chromatography for increased purity

• Quality assessment methods:

  • SDS-PAGE analysis (target >90% purity)

  • Western blotting for identity confirmation

  • Circular dichroism for secondary structure verification

Based on research with other ATP synthase subunits, obtaining properly folded atpF may require reconstitution into nanodiscs or liposomes to maintain native-like membrane environments .

What methods can be used to study atpF interactions within the ATP synthase complex?

Understanding the interactions of atpF within the ATP synthase complex is crucial for elucidating its function. Several complementary approaches can provide valuable insights:

Polyclonal antibodies against ATP synthase subunits have proven valuable for studying protein expression and interactions, as demonstrated with yeast ATP synthase subunit d . Similar approaches could be adapted for studying Dehalococcoides ethenogenes atpF interactions.

How does atpF contribute to energy metabolism during reductive dehalogenation?

ATP synthase, including its atpF subunit, plays a critical role in energy conservation during reductive dehalogenation by Dehalococcoides ethenogenes. This bacterium's unique metabolism involves using chlorinated compounds as terminal electron acceptors in an anaerobic respiratory process .

The energy conversion pathway involves:

• Electron transfer from hydrogen (electron donor) to chlorinated compounds via reductive dehalogenases

• Establishment of a proton gradient across the cell membrane during electron transport

• Utilization of this proton gradient by ATP synthase to generate ATP

The b subunit (atpF) forms part of the peripheral stalk that prevents rotation of the α3β3 headpiece while allowing rotation of the c-ring and γ subunit, thus enabling efficient energy coupling. The properties of atpF likely reflect adaptations to the relatively low energy yield of reductive dehalogenation reactions compared to other respiratory processes.

Methodological approaches to study this function include:

• Bioenergetic measurements to determine H+/ATP ratios specific to Dehalococcoides

• Inhibitor studies to correlate ATP synthesis with dehalogenation rates

• Comparative genomics across Dehalococcoides strains to identify adaptive features in ATP synthase components

What genetic approaches can be used to study atpF function in Dehalococcoides ethenogenes?

• Gene deletion/replacement strategies:

  • Design of recombination constructs with homologous flanking regions

  • Selection using antibiotic resistance markers (e.g., kanamycin resistance)

  • PCR verification followed by restriction digest and sequencing confirmation

The methodology demonstrated with Heliomicrobium modesticaldum gene deletion provides a template that could be adapted for Dehalococcoides ethenogenes:

• Amplification of genomic regions flanking the target gene

• Introduction of selection markers between these flanking regions

• Double homologous recombination for marker insertion

• Screening for successful recombinants using PCR and restriction enzyme analysis

• Complementation studies:

  • Construction of expression vectors containing wild-type or mutant atpF variants

  • Introduction into deletion strains to assess functional recovery

  • Analysis of growth rates and ATP synthesis to quantify complementation efficacy

• Site-directed mutagenesis approaches:

  • Targeted modification of conserved residues or domains

  • Expression of mutant variants in native or heterologous systems

  • Structure-function analysis through biochemical and biophysical methods

How does Dehalococcoides ethenogenes ATP synthase compare to other bacterial ATP synthases?

Comparative analysis of ATP synthase components across bacterial species provides insights into evolutionary adaptations and functional specialization:

The unique ecological niche of Dehalococcoides ethenogenes as a strictly anaerobic dechlorinating bacterium likely imposes specific selective pressures on its energy conservation machinery. Comparative genomic analysis has revealed high gene context conservation (synteny) in many regions of the genome when compared with related strains, suggesting functional importance of these conserved arrangements .

What role does Dehalococcoides ethenogenes play in environmental bioremediation?

Dehalococcoides ethenogenes has significant applications in environmental bioremediation due to its unique metabolic capabilities:

• Reductive dehalogenation capacity:

  • Genome sequencing has revealed 32 reductive-dehalogenase-homologous (rdh) genes

  • This extensive genetic repertoire confers an immense potential for degrading diverse chlorinated compounds

• Demonstrated remediation applications:

  • Successful application in in-situ bioremediation of contaminated sites

  • Particularly valuable for complete dechlorination of compounds like vinyl chloride to non-toxic ethene

• Research approaches to enhance bioremediation potential:

  • Characterization of energy metabolism to optimize growth conditions

  • Understanding ATP synthase function to improve energy conservation efficiency

  • Development of biomarkers for monitoring Dehalococcoides activity at remediation sites

The bacterium's metabolic efficiency, including ATP production via ATP synthase, directly impacts its growth rate and dechlorination capacity, making understanding of the ATP synthase complex crucial for optimizing bioremediation applications.

How can structural studies of atpF inform understanding of ATP synthase assembly and function?

Structural studies of Dehalococcoides ethenogenes atpF can provide critical insights into ATP synthase assembly and function through several approaches:

• High-resolution structural determination methods:

  • X-ray crystallography of isolated atpF or subcomplexes

  • Cryo-electron microscopy of intact ATP synthase complexes

  • NMR spectroscopy for dynamic structural information

• Functional implications of structural features:

  • Identification of conserved residues at protein-protein interfaces

  • Characterization of the transmembrane domain and its membrane interactions

  • Analysis of conformational changes during ATP synthesis

• Assembly pathway investigation:

  • In vitro reconstitution experiments with purified components

  • Time-resolved structural studies during complex formation

  • Identification of assembly intermediate states

The amino acid sequence provided for atpF can serve as the foundation for structural predictions and experimental design, with the ultimate goal of understanding how atpF contributes to the assembly, stability, and functional mechanism of the complete ATP synthase complex.

What challenges may researchers encounter when working with Dehalococcoides ethenogenes cultures?

Working with Dehalococcoides ethenogenes presents several technical challenges due to its strict anaerobic nature and specialized metabolism:

Researchers have developed cultivation techniques for Dehalococcoides strains that include the use of defined mineral media supplemented with hydrogen as an electron donor and appropriate chlorinated compounds as electron acceptors .

How can researchers address solubility and stability issues with recombinant atpF?

Recombinant Dehalococcoides ethenogenes atpF, like many membrane proteins, presents solubility and stability challenges that can be addressed through optimized protocols:

• Improving initial solubility:

  • Fusion partners (MBP, SUMO, GST) to enhance soluble expression

  • Co-expression with chaperones to assist proper folding

  • Lower induction temperatures (16-20°C) and reduced inducer concentrations

• Stabilization approaches for purified protein:

  • Optimization of buffer composition (pH, ionic strength, additives)

  • Addition of stabilizing agents (trehalose 6%, glycerol 5-50%)

  • Testing various detergents for membrane protein stabilization

• Extraction from inclusion bodies:

  • Carefully controlled solubilization in denaturants (urea, guanidine HCl)

  • Stepwise dialysis in the presence of non-ionic detergents

  • Monitoring refolding by circular dichroism or fluorescence spectroscopy

Based on experience with similar proteins, inclusion body solubilization in urea followed by gradual detergent-assisted refolding has proven effective for obtaining functional membrane proteins .

What analytical methods are most suitable for assessing atpF quality and functionality?

Comprehensive quality assessment of recombinant Dehalococcoides ethenogenes atpF requires multiple analytical approaches:

For ATP synthase components, functional assessment often involves reconstitution into liposomes followed by ATP synthesis/hydrolysis assays, although these are technically challenging and require additional ATP synthase components .

What emerging technologies could advance research on Dehalococcoides ethenogenes atpF?

Several cutting-edge technologies show promise for addressing current limitations in Dehalococcoides ethenogenes atpF research:

• Advanced structural biology approaches:

  • Single-particle cryo-EM for structure determination without crystallization

  • Integrative structural biology combining multiple data sources (crosslinking-MS, SAXS, computational modeling)

  • Time-resolved structural methods to capture dynamic states

• Genetic engineering advances:

  • CRISPR-Cas9 adaptation for anaerobic organisms

  • Improved transformation protocols for recalcitrant bacteria

  • Development of inducible gene expression systems for Dehalococcoides

• Synthetic biology approaches:

  • Minimal ATP synthase reconstructions with defined components

  • Designer ATP synthase variants with altered properties

  • Cell-free expression systems optimized for membrane proteins

• Advanced biophysical techniques:

  • Single-molecule FRET to study conformational dynamics

  • High-resolution microscopy of ATP synthase in native membranes

  • Nanoscale thermophoresis for interaction studies

These technologies could overcome current limitations in understanding atpF structure, function, and interactions within the ATP synthase complex and cellular context.

How might understanding atpF function contribute to enhancing bioremediation applications?

Detailed knowledge of Dehalococcoides ethenogenes atpF function could significantly impact bioremediation applications through several mechanisms:

• Improving bioremediation efficiency:

  • Understanding energy conservation limitations in Dehalococcoides

  • Identifying bottlenecks in ATP production during reductive dehalogenation

  • Developing strategies to enhance energy capture and growth rates

• Bioprocess optimization approaches:

  • Tailoring growth conditions to maximize ATP synthase efficiency

  • Designing bioreactors with optimal conditions for ATP synthesis

  • Developing biomarkers based on ATP synthase activity to monitor remediation progress

• Potential biotechnological applications:

  • Engineering strains with enhanced ATP synthase efficiency

  • Developing biosensors based on ATP synthase components

  • Creating specialized strains for different chlorinated contaminants

The central role of ATP synthase in energy conservation directly impacts the growth and metabolic activity of Dehalococcoides ethenogenes, making it a key target for improving bioremediation outcomes for chlorinated contaminants .