Recombinant Salmonella newport ATP synthase subunit a (atpB)

What is the structure and function of ATP synthase in Salmonella newport?

ATP synthase in Salmonella newport, like in other bacteria, is a multi-subunit enzyme complex that catalyzes ATP synthesis through a proton gradient across the membrane. The enzyme consists of two major components: F₁ (containing the catalytic sites) and F₀ (the membrane-embedded proton channel). Subunit c (atpE) forms part of the F₀ sector and functions in proton translocation across the membrane, while subunit a (atpB) interacts with subunit c in the membrane-bound portion to facilitate proton movement. The F₀ sector converts the energy of proton movement into mechanical rotation, which drives ATP synthesis in the F₁ sector.

What is known about the amino acid sequence of Salmonella newport ATP synthase subunit c?

Recombinant Full Length Salmonella newport ATP synthase subunit c (atpE) protein consists of 79 amino acids. According to available data, the amino acid sequence is: MENLNMDLLYMAAAVMMGLAAIGAAIGIGILGGKFLEGAARQPDLIPLLRTQFFIVMGLVDAIPMIAVGLGLYVMFAVA . This highly hydrophobic sequence is typical of membrane-embedded proteins and contains conserved residues essential for proton translocation. The protein has a UniProt ID of B4SYD6 and may also be referred to as "lipid-binding protein" due to its interactions with membrane phospholipids .

What expression systems are recommended for recombinant Salmonella ATP synthase subunits?

For recombinant production of Salmonella newport ATP synthase subunits, E. coli expression systems have proven effective. As demonstrated with the atpE subunit, expression in E. coli with an N-terminal His-tag provides good yields of purifiable protein . When selecting an expression system, researchers should consider:

• Codon optimization for the host organism

• Inclusion of appropriate affinity tags (His-tag is commonly used)

• Selection of promoters compatible with membrane protein expression

• Induction conditions that balance protein yield with proper folding

• Growth conditions that minimize formation of inclusion bodies

E. coli is particularly suitable for expressing Salmonella proteins due to their genetic relatedness, similar codon usage, and the availability of numerous specialized expression vectors.

How do antimicrobial resistance patterns in Salmonella newport relate to ATP synthase function?

While direct correlations between ATP synthase mutations and antimicrobial resistance in Salmonella newport have not been extensively documented in the provided search results, research on MDR-AmpC isolates reveals important patterns. Salmonella newport MDR-AmpC isolates show resistance to at least nine antimicrobials, including extended-spectrum cephalosporins . These resistance patterns appear more frequently in cattle isolates (93%) compared to human (53%), swine (70%), or chicken (30%) isolates .

What are the optimal purification methods for recombinant Salmonella newport ATP synthase subunits?

Purification of recombinant Salmonella ATP synthase subunits requires careful consideration of their hydrophobic nature and membrane association. Based on the information for atpE:

• Initial Preparation: Express protein with an N-terminal His-tag in E. coli

• Harvesting: Centrifugation followed by cell lysis under conditions that maintain protein integrity

• Affinity Chromatography: Ni-NTA or similar metal affinity chromatography using the His-tag

• Detergent Selection: Critical for membrane proteins; detergents like DDM, LDAO, or OG should be empirically tested

• Buffer Optimization: Tris/PBS-based buffers at pH 8.0 have been successful

• Stabilization: Addition of 6% trehalose helps maintain protein stability

• Storage: Final preparation as lyophilized powder or in solution with 50% glycerol at -20°C/-80°C

When designing purification protocols, researchers should avoid repeated freeze-thaw cycles as these significantly reduce protein activity and integrity .

How can researchers distinguish between Salmonella newport strains based on ATP synthase genetic variations?

While ATP synthase genes are not typically used as primary markers for distinguishing Salmonella newport strains, combining ATP synthase sequence analysis with established typing methods could provide additional discrimination power. Current methods for characterizing Salmonella newport strains include:

• Pulsed-field gel electrophoresis (PFGE): Studies have identified at least 35 distinct PFGE patterns among Salmonella newport isolates

• Antimicrobial susceptibility testing: Differentiating between pansusceptible (88% of isolates) and resistant strains (particularly MDR-AmpC which constitute about 8% of isolates)

• Class 1 integron detection: Present in approximately 40% of isolates

• blaCMY gene detection: Present in all MDR-AmpC isolates

To incorporate ATP synthase gene analysis, researchers could:

• Perform targeted sequencing of ATP synthase operon regions

• Develop PCR-based methods to detect specific polymorphisms

• Use whole genome sequencing to analyze ATP synthase genes in the context of the entire genome

• Apply computational approaches to identify correlations between ATP synthase variations and phenotypic traits

What strategies can be employed to study interactions between different ATP synthase subunits in Salmonella?

Studying interactions between ATP synthase subunits requires sophisticated approaches due to the complex nature of the multiprotein assembly. Researchers can employ:

• Co-immunoprecipitation: Using antibodies against one subunit to pull down interacting partners

• Crosslinking studies: Chemical crosslinking followed by mass spectrometry to identify interaction interfaces

• FRET analysis: Tagging different subunits with fluorescent proteins to monitor proximity in vivo

• Bacterial two-hybrid systems: Adapted for membrane protein interactions

• Reconstitution studies: Purifying individual subunits and reconstituting them in vitro to assess complex formation

• Cryo-electron microscopy: To visualize the entire complex and determine subunit arrangement

• Molecular dynamics simulations: To predict interaction interfaces and dynamics

When expressing recombinant subunits for interaction studies, researchers should consider native-like membrane environments or nanodiscs to maintain physiologically relevant conformations.

What factors should be considered when designing reconstitution experiments for ATP synthase components?

Reconstitution of ATP synthase components presents several challenges that researchers must address:

• Protein Source and Purity: Recombinant proteins should be purified to >90% homogeneity, as verified by SDS-PAGE

• Membrane Mimetics: Selection between liposomes, nanodiscs, or detergent micelles based on experimental goals

• Lipid Composition: Consider using lipids that match Salmonella membrane composition

• Protein-to-Lipid Ratio: Typically requires optimization for each preparation

• Buffer Conditions: pH, ionic strength, and presence of stabilizing agents affect reconstitution efficiency

• Assembly Order: Sequential addition of components may be necessary for proper complex formation

• Functional Verification: ATP synthesis/hydrolysis assays or proton pumping measurements

• Structural Verification: Negative-stain EM, AFM, or other techniques to confirm complex formation

When reconstituting the c-subunit (atpE), researchers should pay particular attention to its hydrophobic nature (as evident from its sequence: MENLNMDLLYMAAAVMMGLAAIGAAIGIGILGGKFLEGAARQPDLIPLLRTQFFIVMGLVDAIPMIAVGLGLYVMFAVA) and ensure adequate solubilization throughout the reconstitution process.

How should researchers optimize storage conditions for recombinant ATP synthase subunits?

Proper storage of recombinant ATP synthase subunits is critical for maintaining activity. Based on empirical data for atpE:

Key considerations:

• Aliquoting is necessary to avoid repeated freeze-thaw cycles

• For reconstitution, use deionized sterile water to a concentration of 0.1-1.0 mg/mL

• The addition of 5-50% glycerol (final concentration) is recommended for long-term storage

• Brief centrifugation of vials prior to opening helps bring contents to the bottom

• Storage buffer composition (Tris/PBS-based buffer, 6% Trehalose, pH 8.0) significantly impacts stability

• Working aliquots should be kept at 4°C and used within one week

What controls should be included when studying ATP synthase function in Salmonella newport?

Robust experimental design for ATP synthase functional studies requires several controls:

• Positive Controls:

  • Purified E. coli ATP synthase (well-characterized homolog)

  • ATP synthase from model organisms with known activity parameters

  • Synthetic ATP hydrolysis/synthesis systems

• Negative Controls:

  • Heat-inactivated enzyme preparations

  • Preparations with specific inhibitors (e.g., oligomycin, DCCD)

  • Mutant versions lacking critical catalytic residues

• Experimental Validation Controls:

  • Measurements under varying substrate concentrations

  • pH dependence assays to confirm proton coupling

  • Reconstitution controls with varying lipid compositions

  • Assays in the presence and absence of membrane potential

• Technical Controls:

  • Buffer-only reactions

  • Enzyme storage stability verification

  • Temperature-dependent activity measurements

  • Detergent effect controls if using solubilized preparations

When working with recombinant subunits rather than the complete complex, additional controls should verify that observed activities reflect native-like properties rather than artifacts of the recombinant system.

How can researchers address discrepancies when comparing ATP synthase activity across different Salmonella serotypes?

When comparing ATP synthase activity across different Salmonella serotypes, researchers must consider several factors that might explain observed discrepancies:

• Genetic Variation Analysis:

  • Sequence alignment of ATP synthase genes across serotypes

  • Identification of SNPs in promoter regions affecting expression levels

  • Assessment of operon organization and potential regulatory differences

• Expression Level Normalization:

  • Quantitative PCR to determine transcript levels

  • Western blotting with calibrated standards to quantify protein amounts

  • Proteomics approaches for absolute quantification

• Environmental Adaptation Factors:

  • Different serotypes may optimize ATP synthase for their ecological niches

  • Consider growth conditions of source strains (e.g., host-adapted vs. environmental)

  • Examine potential serotype-specific post-translational modifications

• Methodological Considerations:

  • Standardize purification protocols across serotypes

  • Use identical assay conditions and reagent lots

  • Develop internal standards for activity normalization

  • Consider membrane composition differences when using reconstituted systems

Studies of Salmonella newport should particularly consider its diverse ecological distribution and strain variations across human, cattle, swine, and poultry sources, which show different antimicrobial resistance patterns that might correlate with metabolic adaptations.

What approaches help distinguish between direct effects on ATP synthase and secondary metabolic consequences when studying Salmonella mutants?

Distinguishing primary effects on ATP synthase from secondary metabolic consequences requires multifaceted approaches:

• Genetic Complementation Studies:

  • Reintroduce wild-type genes into mutant strains to verify phenotype restoration

  • Use inducible expression systems to establish dose-dependency

  • Create point mutations affecting specific functions rather than gene deletions

• Metabolomics Analysis:

  • Compare metabolite profiles between wild-type and mutant strains

  • Track isotope-labeled substrates to identify altered metabolic flux

  • Measure ATP/ADP ratios and proton motive force components separately

• Temporal Studies:

  • Monitor changes immediately following genetic perturbation

  • Establish time-course experiments to separate primary from secondary effects

  • Use inducible systems to trigger ATP synthase disruption and observe immediate consequences

• Biochemical Isolation:

  • Purify ATP synthase complexes from mutant and wild-type strains for direct in vitro comparison

  • Reconstitute purified components in controlled membrane environments

  • Use inhibitors with specific targets to separate ATP synthase effects from other processes

• Systems Biology Approaches:

  • Integrate transcriptomics, proteomics, and metabolomics data

  • Apply computational modeling to identify direct consequence networks

  • Compare observed patterns with predicted effects based on ATP synthase function

These approaches are particularly relevant given the complex phenotypes observed in Salmonella newport strains with varying antimicrobial resistance profiles , which likely involve multiple interacting metabolic adaptations.