Recombinant Arcobacter butzleri ATP synthase subunit a (atpB)

What is the genomic context of the atpB gene in Arcobacter butzleri?

The atpB gene in A. butzleri is part of the ATP synthase operon, similar to other Epsilonproteobacteria. While specific information about atpB is limited in the available literature, genomic analysis of A. butzleri strain RM4018 reveals substantial genomic differences from related Campylobacteraceae, with its proteome showing greater similarity to Sulfuromonas denitrificans and Wolinella succinogenes . The complete genome sequence of A. butzleri strain RM4018 consists of a single chromosome of approximately 2.3 million base pairs, with numerous genes devoted to growth and survival under diverse environmental conditions . This includes a large number of respiration-associated proteins that could potentially interact with ATP synthase functionality.

How evolutionarily conserved is the ATP synthase subunit a across Arcobacter species?

ATP synthase subunits are generally well-conserved across bacterial species due to their essential function. Comparative genomic analysis of A. butzleri strains reveals both core genes and hypervariable regions . Analysis of 12 additional A. butzleri strains beyond the reference strain RM4018 has helped to identify the core genome of this species, which likely includes the essential ATP synthase components .

How does A. butzleri ATP metabolism compare to other Epsilonproteobacteria?

A. butzleri has a unique metabolic profile compared to other Epsilonproteobacteria. The organism possesses a distinctive central metabolism with modifications to the typical TCA cycle found in other bacteria . While A. butzleri encodes several proteins homologous to other epsilonproteobacterial TCA cycle enzymes, it also has unique features including two predicted aconitate hydratases and two fumarate dehydratases . Additionally, enzymes that catalyze two TCA cycle steps appear to be absent in strain RM4018 .

This modified energy metabolism suggests that ATP synthesis in A. butzleri may have unique characteristics or regulatory mechanisms. The organism grows on fumarate, lactate, malate, and pyruvate, but not on acetate, citrate, or propionate , indicating specific substrate preferences that would affect ATP production pathways.

What structural features might distinguish A. butzleri ATP synthase from those of related pathogens?

While specific structural information about A. butzleri ATP synthase subunit a is not directly available in the current literature, extrapolation from genomic analyses suggests potential unique features. A. butzleri shows significant genomic divergence from Campylobacter and Helicobacter species, with many of its proteins sharing higher similarity to those from Sulfuromonas denitrificans, Wolinella succinogenes, and deep-sea vent Epsilonproteobacteria .

For structural prediction studies, researchers should consider:

• Performing multiple sequence alignments of atpB with homologs from related species

• Using homology modeling based on crystallized bacterial ATP synthases

• Identifying conserved functional motifs involved in proton translocation

• Analyzing potential unique residues that might confer specialized functions

The adaptation of A. butzleri to diverse environmental conditions may be reflected in structural adaptations of its ATP synthase that optimize function under various pH, temperature, or oxygen conditions.

How might recombinant A. butzleri ATP synthase subunit a be utilized to study antimicrobial resistance mechanisms?

A. butzleri is described as an emergent pathogen with increasing rates of multidrug resistance . Research on its ATP synthase could reveal connections between energy metabolism and antimicrobial resistance mechanisms. Recent work has demonstrated the contribution of efflux systems like YbhFSR in A. butzleri to resistance against various compounds . ATP-dependent efflux pumps require energy generated by ATP synthase to function.

A methodological approach could include:

• Generating recombinant ATP synthase subunit a with site-directed mutations

• Measuring ATP production efficiency in wild-type versus mutant proteins

• Correlating ATP synthase activity with expression levels of ATP-dependent efflux pumps

• Testing if ATP synthase inhibitors potentiate antimicrobial efficacy in resistant strains

A particular focus could be on the relationship between ATP synthase function and the ABC efflux system, as YbhF has been characterized as an ATP-binding component with ATP-binding domains that are essential for the energy process of the efflux pump in A. butzleri .

What is the predicted proton-conducting mechanism in A. butzleri ATP synthase subunit a?

The proton-conducting mechanism in ATP synthase subunit a typically involves conserved charged residues that form a pathway for proton translocation. For A. butzleri, researchers could:

• Identify conserved arginine and aspartate residues in the predicted transmembrane helices

• Compare these with well-characterized proton channels in E. coli and other bacteria

• Design experiments using pH-sensitive fluorescent probes to measure proton translocation

• Perform site-directed mutagenesis to test the role of predicted key residues

The unique environmental adaptations of A. butzleri may have led to specializations in its proton-conducting mechanism. The organism's ability to grow under diverse conditions suggests potential adaptations in its ATP synthase to maintain function across varying proton gradients.

What expression systems are optimal for producing functional recombinant A. butzleri ATP synthase subunit a?

Expressing membrane proteins like ATP synthase subunit a presents significant challenges. Based on research with similar bacterial membrane proteins, researchers should consider:

For A. butzleri proteins specifically, consider:

• Using low GC-content optimized expression vectors to match A. butzleri's 27.16% GC content

• Co-expressing with chaperones to assist proper folding

• Including a fusion partner (MBP, SUMO) to enhance solubility

• Expressing the entire ATP synthase operon to promote proper complex assembly

What purification strategies maintain the structural integrity of A. butzleri ATP synthase subunit a?

Purification of membrane proteins requires careful selection of detergents and buffer conditions. A methodological approach should include:

• Initial solubilization screening:

  • Test multiple detergents (DDM, LMNG, DMNG) at various concentrations

  • Evaluate solubilization efficiency by Western blot

  • Assess protein stability using thermal shift assays

• Chromatography sequence:

  • IMAC (Immobilized Metal Affinity Chromatography) for initial capture

  • Size exclusion chromatography to remove aggregates

  • Consider ion exchange as a polishing step

• Critical buffer components:

  • Include glycerol (10-20%) to stabilize the protein

  • Maintain physiologically relevant pH (6.5-7.5)

  • Add lipids (E. coli total lipid extract) to stabilize the protein

• Quality control metrics:

  • SEC-MALS to assess oligomeric state

  • Negative stain EM to confirm structural integrity

  • Functional assays (ATP hydrolysis) to verify activity

How can researchers validate the functionality of recombinant A. butzleri ATP synthase subunit a?

Validating functionality of recombinant ATP synthase subunit a requires multiple complementary approaches:

• ATP synthesis/hydrolysis assays:

  • Reconstitute purified protein into liposomes

  • Measure ATP synthesis driven by artificial proton gradient

  • Assess ATP hydrolysis activity using coupled enzyme assays

• Proton translocation measurements:

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

  • Monitor pH changes in proteoliposomes upon ATP addition

  • Compare activities to well-characterized bacterial ATP synthases

• Structural validation:

  • Circular dichroism to confirm secondary structure content

  • Limited proteolysis to assess proper folding

  • Crosslinking studies to verify interaction with other ATP synthase subunits

• In vivo complementation:

  • Express recombinant A. butzleri atpB in ATP synthase-deficient E. coli

  • Assess restoration of growth on non-fermentable carbon sources

  • Measure membrane potential using fluorescent probes

What critical residues in A. butzleri ATP synthase subunit a contribute to proton translocation?

Identifying critical residues requires systematic mutagenesis combined with functional assays. A methodological approach includes:

• Alanine scanning mutagenesis of:

  • Conserved charged residues (Arg, Asp, Glu) in transmembrane domains

  • Residues at predicted helix-helix interfaces

  • Residues conserved across Epsilonproteobacteria but divergent from other bacteria

• Functional characterization of mutants:

  • ATP synthesis and hydrolysis rates

  • Proton translocation efficiency

  • Protein stability and complex assembly

• Computational approaches:

  • Molecular dynamics simulations of wild-type and mutant proteins

  • Electrostatic surface mapping to identify potential proton pathways

  • Coevolution analysis to identify functionally coupled residues

The unique environmental adaptations of A. butzleri, including growth under diverse conditions , may be reflected in specialized residues that allow ATP synthase to function across varying conditions.

How does the structure of A. butzleri ATP synthase subunit a contribute to antimicrobial resistance?

While ATP synthase is not typically considered a direct antimicrobial resistance determinant, energy metabolism plays a crucial role in resistance mechanisms. Research approaches should include:

• Investigating potential interactions between ATP synthase and efflux systems:

  • The YbhFSR system in A. butzleri has been shown to contribute to resistance against benzalkonium chloride, ethidium bromide, and cadmium

  • ATP-binding is essential for the function of this efflux system

  • Investigate if ATP synthase inhibition affects efflux pump activity

• Exploring metabolic adaptations in resistant strains:

  • Compare ATP synthase expression and activity between resistant and sensitive strains

  • Assess if ATP synthase mutations correlate with resistance phenotypes

  • Determine if energy metabolism shifts occur in response to antimicrobial exposure

• ATP synthase as a potential drug target:

  • Design inhibitors specific to A. butzleri ATP synthase

  • Assess synergistic effects with conventional antibiotics

  • Evaluate impact on bacterial viability under various growth conditions

The connection between ATP synthesis and antimicrobial resistance is particularly relevant given A. butzleri's emerging pathogen status and increasing multidrug resistance rates .

How might understanding A. butzleri ATP synthase structure inform new antimicrobial development?

ATP synthase represents a potential drug target due to its essential role in energy metabolism. Research approaches should include:

• Structure-based drug design targeting unique features of A. butzleri ATP synthase:

  • Identify binding pockets unique to A. butzleri ATP synthase

  • Design small molecules that selectively inhibit bacterial but not human ATP synthase

  • Screen compound libraries for inhibitory activity

• Exploring known ATP synthase inhibitors:

  • Test bedaquiline (tuberculosis drug targeting ATP synthase) against A. butzleri

  • Assess oligomycin derivatives for selective inhibition

  • Develop A. butzleri-specific derivatives based on existing inhibitors

• Combining ATP synthase inhibition with other approaches:

  • Test synergy with efflux pump inhibitors, particularly targeting YbhFSR system

  • Evaluate combination therapy with conventional antibiotics

  • Assess ATP synthase inhibitors under various environmental conditions relevant to A. butzleri pathogenesis

The increasing rates of multidrug resistance in A. butzleri highlight the need for new antimicrobial targets and approaches.

How does A. butzleri ATP synthase activity vary under different environmental conditions?

A. butzleri has been described as a ubiquitous microorganism capable of surviving in diverse environments. Understanding how its ATP synthase functions across these conditions is critical. Research methods should include:

• In vitro activity measurements under varying conditions:

  • pH range (acidic to alkaline)

  • Temperature range (psychrophilic to mesophilic)

  • Oxygen levels (aerobic, microaerobic, anaerobic)

  • Salt concentrations

• Expression analysis across conditions:

  • qRT-PCR to measure atpB expression under different growth conditions

  • Proteomic analysis to quantify ATP synthase subunit abundance

  • Assess post-translational modifications that might regulate activity

• Correlating energy production with stress responses:

  • Measure ATP levels during exposure to various stressors

  • Compare wild-type and atpB mutant strains for survival under stress

  • Investigate relationships between ATP synthase activity and expression of resistance genes

A. butzleri's ability to survive in diverse environments, including resistance to human serum , suggests specialized adaptations in its energy production systems.

What are the main challenges in structural studies of A. butzleri ATP synthase subunit a and how can they be overcome?

Membrane protein structural studies face numerous technical challenges. For A. butzleri ATP synthase subunit a, specific approaches include:

Additionally, researchers should consider:

• Expressing the entire ATP synthase complex rather than subunit a alone

• Using chimeric constructs with well-characterized ATP synthase components

• Applying integrative structural biology approaches combining multiple techniques

• Developing computational models validated by crosslinking or mutational data

How can researchers differentiate between ATP synthase-dependent and independent energy mechanisms in A. butzleri?

A. butzleri possesses unique metabolic capabilities that might involve both ATP synthase-dependent and independent energy mechanisms. Experimental approaches should include:

• Genetic manipulation strategies:

  • Generate conditional atpB knockdown strains

  • Create point mutations in catalytic sites versus proton channel residues

  • Develop reporter strains with ATP biosensors

• Metabolic flux analysis:

  • Use 13C-labeled substrates to track carbon flow through metabolic pathways

  • Compare flux distributions in the presence of ATP synthase inhibitors

  • Identify alternative ATP-generating pathways

• Bioenergetic measurements:

  • Simultaneously measure membrane potential, pH gradient, and ATP levels

  • Assess oxygen consumption rates with various substrates

  • Determine the effect of uncouplers versus ATP synthase inhibitors

A. butzleri's central metabolism contains several unique features compared to other Epsilonproteobacteria , suggesting potential alternative energy conservation mechanisms that may complement ATP synthase function.