Recombinant Campylobacter concisus ATP synthase subunit c (atpE)

What is ATP synthase subunit c (atpE) in Campylobacter concisus?

ATP synthase subunit c (atpE) is an enzyme component that catalyzes the production of ATP from ADP in the presence of sodium or proton gradient. In Campylobacter concisus strain 13826, the protein consists of 100 amino acids with the sequence: MKKIVFLILGLAAFAFGADGEMIRSYSVIAGGIGLGLAALGGAIGMGNTAAATISGTARNPGVSKLMTTMFIALAIEAQVIYALVITLIVLYANPMLG . This protein is also known by alternative names including ATP synthase F(0) sector subunit c, F-type ATPase subunit c, and Lipid-binding protein. The gene encoding this protein is designated as atpE (locus tag: Ccon26_04820) .

What is the biological function of C. concisus atpE?

C. concisus atpE functions as part of the F-type ATP synthase complex, which plays a crucial role in cellular energy production. The ATP synthase enzyme catalyzes the production of ATP from ADP in the presence of a sodium or proton gradient . Within the bacterial context, ATP synthase provides the energy necessary for various cellular processes, particularly during states of dormancy or limited oxygen availability. The enzyme is especially important for C. concisus as this pathogen inhabits the human oral-gastrointestinal tract and can grow under both microaerobic and anaerobic conditions .

What structural characteristics define C. concisus atpE?

The C. concisus atpE protein exhibits classical structural features of ATP synthase subunit c proteins. Key structural characteristics include:

• A transmembrane orientation with hydrophobic domains that anchor the protein within the membrane

• Conserved residues that participate in proton translocation

• A ring-like assembly in the native complex, with multiple c-subunits forming a rotor structure

• Specific binding sites for inhibitors such as DCCD (dicyclohexylcarbodiimide)

The protein consists of 100 amino acids and contains regions that facilitate its integration into the bacterial membrane, allowing it to participate in the proton gradient-driven ATP synthesis mechanism .

How can the recombinant C. concisus atpE protein be optimally stored and handled?

For optimal storage and handling of recombinant C. concisus atpE:

• Store the protein at -20°C for short-term use, or at -80°C for extended storage

• For working stocks, prepare aliquots to avoid repeated freeze-thaw cycles

• Working aliquots can be maintained at 4°C for up to one week

• The protein is typically supplied in a Tris-based buffer with 50% glycerol, optimized for stability

• When using the protein for experiments, thaw aliquots slowly on ice to prevent denaturation

• Centrifuge briefly after thawing to collect any precipitated material

This approach minimizes protein degradation and maintains functional integrity for experimental applications.

What experimental methods are recommended for studying C. concisus atpE function?

To effectively study C. concisus atpE function, researchers should consider the following methodological approaches:

• ATP Synthesis Assays: Measure ATP production in reconstituted proteoliposomes containing purified ATP synthase complexes under varying pH gradients.

• Inhibitor Studies: Evaluate the effects of known ATP synthase inhibitors such as:

  • DCCD (dicyclohexylcarbodiimide)

  • NBD-Cl (7-chloro-4-nitrobenzo-2-oxa-1,3-diazole)

  • Sodium azide (NaN₃)

  • Metal fluorides (AlFₓ, ScFₓ, BeFₓ)

  • Natural inhibitors like oligomycin and resveratrol

• Proton Translocation Measurements: Assess proton movement using pH-sensitive fluorescent dyes.

• Site-Directed Mutagenesis: Introduce specific mutations to identify crucial residues for function, particularly those involved in proton binding or inhibitor interaction.

• Protein-Protein Interaction Studies: Investigate interactions between atpE and other subunits of the ATP synthase complex using techniques such as co-immunoprecipitation or crosslinking studies.

These methods provide a comprehensive toolset for exploring the functional properties of C. concisus atpE in various experimental contexts.

How can C. concisus atpE be utilized in drug discovery research against Campylobacteriosis?

C. concisus atpE represents a promising target for antimicrobial development based on the following research approaches:

• High-Throughput Screening (HTS): Develop ATP synthase activity assays suitable for screening large compound libraries to identify novel inhibitors.

• Structure-Based Drug Design: Utilize the known structural features of atpE to design molecules that specifically interact with critical functional regions.

• Repurposing Studies: Test known ATP synthase inhibitors from other bacterial systems, particularly those effective against E. coli or M. tuberculosis ATP synthases .

• Natural Product Exploration: Investigate natural compounds like polyphenols (resveratrol, piceatannol, quercetin) that have demonstrated inhibitory effects on bacterial ATP synthases .

• Comparative Studies: Design inhibitors that selectively target bacterial ATP synthase while sparing human mitochondrial ATP synthase, focusing on structural differences between the two.

The methodological approach should include confirming that candidate compounds inhibit ATP synthesis, testing their efficacy against C. concisus growth in both microaerobic and anaerobic conditions, and evaluating their effects on bacterial persistence in relevant infection models.

What is the relationship between C. concisus atpE and bacterial persistence during infection?

The relationship between C. concisus atpE and bacterial persistence involves several key mechanisms:

• Energy Production During Dormancy: ATP synthase remains critical during dormant states when bacteria have limited metabolic activity, enabling survival under stress conditions .

• Adaptation to Microenvironments: C. concisus can grow under both microaerobic and anaerobic conditions, with ATP synthase facilitating adaptation to the varying oxygen levels encountered throughout the gastrointestinal tract .

• Resistance to Host Defenses: Efficient energy production supports bacterial responses to host immune mechanisms and environmental stresses.

• Biofilm Formation Support: ATP production provides the energy necessary for establishing and maintaining biofilms, which are known contributors to bacterial persistence.

Research methodologies to investigate this relationship should include:

• Creating atpE mutants with altered function to assess impacts on persistence

• Developing in vitro models that simulate the intestinal microenvironment

• Examining ATP synthase activity under various stress conditions relevant to host colonization

What controls should be included when conducting inhibitor studies with C. concisus atpE?

When designing inhibitor studies targeting C. concisus atpE, researchers should implement the following controls:

• Positive Controls:

  • Known ATP synthase inhibitors such as DCCD, NBD-Cl, or oligomycin at established effective concentrations

  • Concentration gradients of positive controls to establish dose-response relationships

• Negative Controls:

  • Vehicle controls (solvents used for compound dissolution)

  • Structurally similar but non-inhibitory compounds

  • Heat-inactivated enzyme preparations

• Specificity Controls:

  • Testing effects on other membrane proteins to ensure specificity

  • Parallel testing on human ATP synthase to assess selectivity

  • Testing on related bacterial species' ATP synthases for comparative analysis

• Functional Validation:

  • Measuring ATP synthesis directly rather than relying solely on binding assays

  • Assessing bacterial growth under conditions where ATP synthase function is essential

  • Monitoring proton gradient dissipation

• Technical Controls:

  • Multiple biological replicates

  • Independent preparation batches of recombinant protein

  • Time-course measurements to capture kinetic effects

These controls collectively ensure the validity, specificity, and reliability of inhibitor study results.

How can researchers accurately assess ATP synthase activity in C. concisus?

To accurately measure ATP synthase activity in C. concisus, researchers should consider these methodological approaches:

• Inverted Membrane Vesicle Assays:

  • Prepare inverted membrane vesicles from C. concisus

  • Measure ATP synthesis upon establishment of a proton gradient

  • Use luciferase-based luminescence assays to quantify ATP production

• Purified Enzyme Complex Studies:

  • Reconstitute purified ATP synthase into proteoliposomes

  • Create an artificial proton gradient

  • Monitor ATP synthesis rates under various conditions

• Proton Translocation Measurements:

  • Use pH-sensitive fluorescent dyes (e.g., ACMA, pyranine)

  • Quantify proton movement across membranes in response to ATP hydrolysis or synthesis

• Oxygen Consumption Analysis:

  • Employ respirometry techniques to measure oxygen consumption linked to ATP synthesis

  • Use specific inhibitors to distinguish ATP synthase contribution

• Genetic Complementation:

  • Create atpE mutants with selective deficiencies

  • Assess restoration of function with wild-type or modified atpE proteins

A comprehensive experimental design should incorporate multiple methods to obtain corroborating evidence of ATP synthase activity and its modulation by experimental conditions or inhibitors.

What are the major technical challenges in working with recombinant C. concisus atpE?

Researchers face several technical challenges when working with recombinant C. concisus atpE:

• Protein Stability Issues:

  • Challenge: atpE's hydrophobic nature can lead to aggregation and insolubility

  • Solution: Optimize buffer conditions with appropriate detergents; use fusion tags that enhance solubility; store in 50% glycerol at appropriate temperatures

• Functional Reconstitution:

  • Challenge: Maintaining native structural conformation during purification

  • Solution: Gentle purification methods; reconstitution into lipid bilayers with compositions similar to C. concisus membranes

• Assay Sensitivity:

  • Challenge: Detecting activity in recombinant systems

  • Solution: Develop highly sensitive coupled assays; optimize enzyme:substrate ratios; use advanced detection methods like bioluminescence

• Structural Analysis Difficulties:

  • Challenge: Obtaining structural information for membrane proteins

  • Solution: Employ techniques optimized for membrane proteins such as cryo-EM; use computational models informed by homologous proteins

• Expression System Limitations:

  • Challenge: Expressing functional bacterial membrane proteins

  • Solution: Test multiple expression systems; consider cell-free expression systems; optimize codon usage for expression host

These technical solutions enhance the feasibility of studying recombinant C. concisus atpE in various experimental contexts.

How can researchers differentiate between the roles of atpE and other energy-producing pathways in C. concisus?

Differentiating between atpE and other energy-producing pathways in C. concisus requires a multi-faceted experimental approach:

• Genetic Manipulation Strategies:

  • Generate specific atpE knockout/knockdown mutants

  • Create conditional expression systems to modulate atpE levels

  • Complement with wild-type or mutant variants to confirm phenotype specificity

• Metabolic Pathway Analysis:

  • Use metabolomics to track energy metabolite fluctuations

  • Employ 13C-labeled substrates to trace carbon flow through different pathways

  • Measure NAD+/NADH and ATP/ADP ratios under various conditions

• Selective Inhibition Approach:

  • Apply specific inhibitors of ATP synthase (e.g., DCCD) alongside inhibitors of other pathways

  • Assess cellular energy status and growth under different inhibition conditions

  • Analyze the additive or synergistic effects of pathway inhibition

• Growth Condition Manipulation:

  • Vary oxygen availability to shift between respiratory modes

  • Alter electron acceptor availability (e.g., N- or S-oxides)

  • Assess the contribution of ATP synthase under different growth conditions

• Comparative Analysis with BisA Function:

  • Investigate the relationship between ATP synthase and the BisA protein, which plays a dual role in C. concisus metabolism

  • Examine how disruption of one pathway affects the other

This systematic approach helps delineate the specific contribution of atpE to C. concisus energy metabolism relative to other pathways.

How does atpE function contribute to C. concisus pathogenesis?

The contribution of atpE to C. concisus pathogenesis involves several interconnected mechanisms:

• Energy Production for Virulence:

  • ATP synthase provides the energy necessary for expressing virulence factors

  • Supports motility mechanisms required for tissue colonization

  • Enables protein synthesis during host adaptation

• Survival Under Host Conditions:

  • Facilitates adaptation to the varying oxygen levels in the gastrointestinal tract (microaerobic to anaerobic)

  • Supports bacterial persistence during nutrient limitation

  • Enables growth in the presence of host defense mechanisms

• Biofilm Support:

  • Provides energy for biofilm formation and maintenance

  • ATP is required for extracellular matrix production

  • Biofilms contribute to antibiotic resistance and immune evasion

• Metabolic Flexibility:

  • ATP synthase functions alongside alternative respiratory pathways (e.g., N- or S-oxide respiration)

  • This metabolic flexibility allows adaptation to changing host environments

  • May facilitate transition between oral and intestinal niches

• Contribution to Disease Manifestations:

  • Energy production supports replication, potentially contributing to inflammatory responses

  • ATP synthase activity may influence the severity of clinical manifestations including diarrhea, fever, and abdominal pain

  • May play a role in post-infectious complications such as reactive arthritis and Guillain-Barré syndrome

Understanding these mechanisms provides insight into potential therapeutic strategies targeting ATP synthase to mitigate C. concisus pathogenesis.

What is the relationship between C. concisus atpE and biofilm formation?

The relationship between C. concisus atpE and biofilm formation represents an important aspect of bacterial persistence and pathogenesis:

• Energy Requirement Mechanism:

  • ATP synthase provides the necessary energy for biosynthetic processes involved in biofilm matrix production

  • Cellular adhesion, a prerequisite for biofilm formation, requires energy-dependent expression of adhesins

  • Quorum sensing systems that regulate biofilm formation depend on ATP availability

• Experimental Approaches for Investigation:

  • Measure biofilm formation capacity in wild-type versus atpE-deficient mutants

  • Quantify biofilm composition and structure using confocal microscopy and biochemical analysis

  • Assess the effects of subinhibitory concentrations of ATP synthase inhibitors on biofilm development

• Environmental Adaptation:

  • ATP synthase activity enables adaptation to the microaerobic or anaerobic conditions within biofilms

  • The ability to utilize alternative terminal electron acceptors (TEAs) may support biofilm growth in oxygen-limited environments

• Stress Response Connection:

  • ATP synthase may contribute to stress tolerance mechanisms that promote biofilm formation

  • BisA protein's role in protein methionine sulfoxide repair may protect against oxidative damage within biofilms

• Comparative Analysis:

  • Similar to observations in S. mutans, inhibition of ATP synthase may reduce biofilm formation and acid production

  • This suggests a conserved role for ATP synthase in biofilm dynamics across bacterial species

This relationship provides potential targets for anti-biofilm strategies in addressing C. concisus infections.

How does C. concisus atpE compare to homologous proteins in other bacterial species?

C. concisus atpE exhibits both conservation and divergence when compared to homologous proteins in other bacterial species:

• Structural Conservation:

  • Core functional domains are conserved across bacterial species

  • Proton-binding residues show high conservation, reflecting the fundamental mechanism of ATP synthesis

  • Transmembrane topology follows similar patterns across diverse bacteria

• Functional Comparison:

  • Similar to M. tuberculosis, ATP synthase plays a vital role during dormancy states

  • Shares inhibitor sensitivity patterns with E. coli ATP synthase for compounds such as DCCD and NBD-Cl

  • May have unique characteristics related to C. concisus' adaptation to the human gastrointestinal environment

• Evolutionary Considerations:

  • atpE exhibits sequence divergence reflecting adaptation to specific ecological niches

  • The protein shows higher conservation in core functional regions versus peripheral domains

  • Genomic context of the atpE gene varies across species, potentially affecting regulation

• Methodological Approach for Comparison:

  • Perform phylogenetic analysis of atpE sequences across related species

  • Conduct structural modeling to identify species-specific features

  • Test cross-species complementation to assess functional conservation

• Inhibitor Sensitivity Profiles:

  • Differential sensitivity to inhibitors can reveal species-specific structural features

  • For example, natural product inhibitors may show variable efficacy across bacterial species

These comparative insights can guide the development of species-specific inhibitors and identify conserved targets for broad-spectrum approaches.

What can be learned from studying atpE variants across different C. concisus strains?

Studying atpE variants across different C. concisus strains provides valuable insights into strain-specific adaptations and functional evolution:

• Strain Diversity and Pathogenicity:

  • Variations in atpE may correlate with differences in virulence between strains

  • Oral strains (e.g., type strain 33237) differ from intestinal strains (e.g., 13826 and 51562) in their metabolic capabilities

  • These differences may reflect adaptation to specific host microenvironments

• Functional Consequences of Variation:

  • Amino acid substitutions may alter proton binding, catalytic efficiency, or inhibitor sensitivity

  • Changes in regulatory regions could affect expression levels under different conditions

  • Post-translational modifications might vary between strains, affecting protein function

• Research Methodology for Strain Comparisons:

  • Sequence and express atpE variants from different strains

  • Compare enzymatic parameters (Km, Vmax, inhibitor sensitivity)

  • Assess the impact of specific variations through site-directed mutagenesis

  • Evaluate growth characteristics under various stress conditions

• Relationship to Other Metabolic Pathways:

  • Variations in atpE may coincide with differences in other energy-producing pathways

  • For example, some strains possess the BisA protein that plays a dual role in respiration and protein repair, while others lack this protein

• Clinical Relevance:

  • Strain-specific variations may correlate with different clinical presentations or post-infectious complications

  • Understanding these variations could inform strain-specific diagnostic and therapeutic approaches

This comparative approach provides a foundation for understanding the evolution of C. concisus energy metabolism and its relationship to pathogenicity.