Recombinant Brucella suis ATP synthase subunit b 1 (atpF1)

How does Brucella suis ATP synthase function in bacterial energy metabolism?

The F0F1 ATP synthase in Brucella suis, like in other bacteria, functions as a reversible nanomotor that can either synthesize ATP when powered by proton gradients or hydrolyze ATP to pump protons across the membrane. Under normal physiological conditions, the enzyme rotates in the "forward" direction, synthesizing >90% of cellular ATP needed for bacterial survival .

The subunit b 1 (atpF1) serves as part of the peripheral stalk (stator) that connects the F1 catalytic domain to the F0 membrane domain. This connection is crucial as it prevents the α3β3 catalytic complex from rotating with the central stalk, allowing the energy of proton flow to be converted into the mechanical energy needed for ATP synthesis. Unlike the inhibitory subunits (ε, ζ, and IF1), atpF1 plays a structural role rather than a regulatory one .

What expression systems are used for producing recombinant Brucella suis atpF1?

Recombinant Brucella suis ATP synthase subunit b 1 (atpF1) is commonly expressed using several host systems:

E. coli is the most frequently used expression system as evidenced by commercial products . When designing experiments with recombinant atpF1, researchers should consider that the expression system may affect protein folding, post-translational modifications, and solubility, potentially impacting functional assays .

How do inhibitory mechanisms of bacterial ATP synthases differ between species, and what implications does this have for Brucella suis atpF1 research?

Instead, α-proteobacteria like Paracoccus denitrificans utilize the ζ subunit for inhibition of ATP hydrolysis. This evolutionary divergence is significant because:

• The ε subunit in α-proteobacteria lost both its inhibitory function and the ATP-binding/sensor motif

• The ζ subunit evolved to replace ε as the primary inhibitor in free-living α-proteobacteria

• Some symbiotic α-proteobacteria have partially lost ζ inhibitory function

• Strictly parasitic α-proteobacteria (Rickettsiales) have completely lost ζ inhibition

This evolutionary pattern suggests that Brucella suis, as an α-proteobacterium, may rely on ζ rather than ε for ATP synthase regulation. Researchers studying atpF1 should consider these species-specific regulatory mechanisms when designing experiments and interpreting results regarding ATP synthase function in Brucella .

What is the potential role of atpF1 in Brucella virulence and pathogenesis?

While direct evidence for atpF1's role in Brucella virulence is limited in the search results, we can infer its importance based on several key points:

• As a component of ATP synthase, atpF1 is essential for energy production during infection and intracellular survival.

• Research on Brucellosis using mouse models has shown that Brucella infection causes hepatic fibrosis and necrosis, suggesting metabolic disruption in host cells . The bacterium's ability to maintain energy homeostasis via ATP synthase likely contributes to this pathology.

• Bacterial ATP synthase inhibition can disrupt membrane potential and pH homeostasis, affecting virulence factor expression and secretion systems.

Researchers investigating atpF1's role in virulence should consider:

• Creating conditional knockdowns rather than complete deletions (as complete deletion may be lethal)

• Measuring ATP synthesis rates during different stages of infection

• Comparing atpF1 sequence and structure between virulent and attenuated Brucella strains

• Investigating potential interactions between atpF1 and host cellular components

How does the evolution of ATP synthase inhibitory mechanisms in α-proteobacteria relate to Brucella suis adaptation?

The evolutionary history of ATP synthase inhibitory mechanisms provides insights into Brucella adaptation:

• Ancestral pattern: Most bacteria utilize the ε subunit as an inhibitor of ATPase activity, with its C-terminal domain switching between compact and extended conformations based on ATP levels .

• α-proteobacterial divergence: The phylogeny shows that α-proteobacteria (including Brucella) diverged in their C-terminal side of ε, losing both the inhibitory function and the ATP-binding/sensor motif (consensus sequence I(L)DXXRA) .

• Replacement mechanism: The ζ subunit evolved in α-proteobacteria to replace ε as the primary inhibitor, suggesting strong evolutionary pressure to maintain ATP conservation mechanisms .

• Parasitic adaptation: Strictly parasitic α-proteobacteria like Rickettsiales have completely lost ζ inhibition, possibly reflecting their highly specialized intracellular lifestyle .

What are recommended storage and handling conditions for recombinant Brucella suis atpF1?

Based on manufacturer recommendations, recombinant Brucella suis atpF1 requires specific storage conditions to maintain stability and activity:

When designing experiments, researchers should:

• Prepare small working aliquots to avoid repeated freeze-thaw cycles

• Thaw protein samples on ice to minimize degradation

• Consider including protease inhibitors if working with crude preparations

• Validate protein activity after extended storage periods

What assays can be used to study inhibition of Brucella ATP synthase activity?

Several established methods can be adapted to study Brucella ATP synthase inhibition:

• ATPase activity assays:

  • Coupled enzyme assays linking ATP hydrolysis to NADH oxidation

  • Colorimetric phosphate release assays using malachite green

  • Luciferase-based ATP consumption measurements

• Membrane potential assays:

  • Fluorescent dyes (TMRM, DiSC3) to measure proton gradient dissipation

  • Potentiometric probes to measure Δψ changes during ATP synthase inhibition

• Inhibitor binding studies:

  • Fluorescence enhancement methods (as used with aurovertin, which shows 50-60 fold fluorescence enhancement upon binding to F1)

  • Surface plasmon resonance to measure binding kinetics of potential inhibitors

  • Thermal shift assays to detect stabilization upon inhibitor binding

• Specific inhibitors as tools:
  While designing experiments, researchers can use established ATP synthase inhibitors as positive controls:

  • Aurovertin (binds β subunit, inhibits uncompetitively)

  • Efrapeptin (binds in the central cavity, inhibits both synthesis and hydrolysis)

  • Resveratrol and piceatannol (bind between γ subunit and β subunit)

When adapting these assays for Brucella ATP synthase, researchers should note that inhibitor sensitivity varies between bacterial species and may not perfectly match established patterns for other bacteria .

How can researchers effectively compare atpF1 function across different Brucella species and strains?

To effectively compare atpF1 function across Brucella species and strains, researchers should employ a comprehensive approach:

• Sequence and structural analysis:

  • Perform multiple sequence alignments of atpF1 across Brucella species

  • Identify conserved domains and variable regions

  • Model structures based on homology to predict functional differences

• Expression analysis:

  • Quantify atpF1 mRNA and protein expression under identical conditions

  • Determine if expression patterns differ during growth phases or stress conditions

  • Use standardized protocols and reference genes for accurate comparisons

• Functional assays:

  • Measure ATP synthesis and hydrolysis rates in membrane preparations

  • Assess proton translocation efficiency using reconstitution systems

  • Compare assembly efficiency of ATP synthase complexes

• Cross-species complementation:

  • Generate atpF1 knockout strains complemented with atpF1 from different species

  • Assess whether cross-species complementation restores normal function

  • Identify specific regions responsible for functional differences through chimeric proteins

• Standardization considerations:

  • Use identical growth conditions and media compositions

  • Normalize data to cell density, total protein, or other relevant parameters

  • Include appropriate statistical analyses to determine significance of observed differences

How should researchers interpret contradictory results when studying recombinant atpF1 compared to native ATP synthase complexes?

When facing contradictory results between recombinant atpF1 studies and native ATP synthase complexes, researchers should consider several factors:

• Structural context effects:
  Recombinant atpF1 in isolation may behave differently than when integrated into the complete ATP synthase complex. The subunit b 1 functions as part of the stator complex, and its interactions with other subunits are crucial for proper function .

• Expression system artifacts:
  Different expression systems (E. coli, yeast, baculovirus, mammalian) may introduce variations in post-translational modifications, folding, or solubility. E. coli-expressed proteins may lack modifications present in native Brucella proteins .

• Protein tag influences:
  Commercial recombinant proteins often contain tags that may interfere with function or interactions. Researchers should compare tagged and untagged versions or use cleavable tags when possible .

• Purity considerations:
  Recombinant protein preparations may contain contaminants that affect assay results. Comparing preparations of different purities (e.g., >90% vs. lower purity) can help identify such effects .

• Reconstitution challenges:
  When reconstituting atpF1 into membranes or complexes, the lipid composition and reconstitution method may affect results and differ from native conditions .

To address these challenges, researchers should:

• Include native membrane preparations as controls

• Perform parallel experiments with multiple expression systems

• Consider the complete ATP synthase complex rather than isolated subunits when possible

• Validate findings using complementary approaches (biochemical, structural, genetic)

• Clearly report experimental conditions to facilitate interpretation of contradictory results

What bioinformatic approaches are most useful for predicting atpF1 structure-function relationships in Brucella suis?

Multiple bioinformatic approaches can be employed to predict atpF1 structure-function relationships:

• Sequence-based methods:

  • Multiple sequence alignments to identify conserved residues across bacterial species

  • Hydrophobicity analysis to predict membrane-spanning regions

  • Coevolution analysis to identify residues that may interact with other subunits

  • Motif scanning to identify functional domains similar to those in related proteins

• Structure prediction tools:

  • Homology modeling based on solved structures of ATP synthase components

  • Ab initio modeling for regions lacking homologous structures

  • Molecular dynamics simulations to predict flexibility and conformational changes

  • Protein-protein docking to predict interactions with other ATP synthase subunits

• Evolutionary analysis:

  • Phylogenetic analysis to understand atpF1 evolution in the context of α-proteobacteria

  • Selection pressure analysis to identify residues under positive or purifying selection

  • Ancestral sequence reconstruction to understand evolutionary trajectories

• Integration with experimental data:

  • Structure prediction constrained by cross-linking data

  • Incorporating cryo-EM or crystallography data of related ATP synthases

  • Using mass spectrometry data to identify post-translational modifications

These approaches should be integrated to develop testable hypotheses about critical residues and regions in atpF1 that can then be validated through site-directed mutagenesis and functional assays .

How might understanding atpF1 contribute to development of antimicrobial strategies against Brucella?

Understanding atpF1 and ATP synthase function in Brucella could inform novel antimicrobial strategies through several mechanisms:

• Direct targeting of ATP synthase:

  • Developing specific inhibitors that bind to unique regions of Brucella ATP synthase

  • Targeting the interface between atpF1 and other subunits to disrupt complex assembly

  • Exploiting differences between bacterial and host ATP synthases to achieve selectivity

• Metabolic vulnerabilities:

  • Identifying conditions where ATP synthase becomes critical for Brucella survival

  • Combining ATP synthase inhibitors with other metabolic inhibitors for synergistic effects

  • Targeting ATP synthase during specific stages of infection when the bacterium is most vulnerable

• Vaccine development approaches:

  • Using recombinant atpF1 as a potential vaccine component

  • Designing attenuated strains with modified ATP synthase function

  • Current research shows mixed results with Brucella abortus RB51 vaccine against Brucella suis, suggesting more targeted approaches may be needed

• Host-pathogen interaction targeting:

  • Understanding how ATP synthase activity affects virulence factor expression

  • Exploring potential interactions between ATP synthase components and host cellular factors

  • Developing strategies to modulate host responses to Brucella infection

• Considerations for drug development:

  • While several natural ATP synthase inhibitors exist (aurovertin, efrapeptin, resveratrol), their specificity varies between species

  • Drug design should account for the unique evolutionary features of α-proteobacterial ATP synthases

  • Potential drug resistance mechanisms should be anticipated and addressed

What are the current challenges in crystallizing ATP synthase components from Brucella species?

Crystallizing ATP synthase components from Brucella presents several specific challenges:

• Membrane protein complexities:

  • The hydrophobic nature of membrane-embedded components like atpF1 makes them difficult to solubilize while maintaining native structure

  • Detergent selection is critical and may require extensive optimization for Brucella proteins

  • Lipid-protein interactions important for function may be disrupted during purification

• Complex assembly issues:

  • ATP synthase functions as a multi-subunit complex, and isolated components may adopt non-native conformations

  • Capturing specific conformational states relevant to the catalytic cycle is technically challenging

  • Stabilizing interactions between subunits may require specific conditions or cross-linking approaches

• Expression and purification obstacles:

  • Recombinant expression may result in inclusion bodies requiring refolding

  • Expression in E. coli may not reproduce native post-translational modifications

  • Purification to the homogeneity required for crystallization (>90%) while maintaining activity is difficult

• Brucella-specific considerations:

  • Biosafety requirements for working with Brucella (BSL-3 pathogen) complicate protein production

  • Limited existing structural information specific to Brucella ATP synthase components

  • Potential species-specific features not present in model organisms

Researchers can address these challenges by:

• Using advanced crystallization techniques like lipidic cubic phase crystallization

• Employing cryo-electron microscopy as an alternative structural approach

• Creating fusion constructs or antibody fragments to stabilize specific conformations

• Leveraging existing structures from related α-proteobacteria as molecular replacement models