Recombinant Salmonella newport ATP synthase subunit b (atpF)

What is Salmonella newport ATP synthase subunit b (atpF) and what is its role in bacterial physiology?

ATP synthase subunit b (atpF) is a critical component of the F₀ sector of the F₀F₁-ATP synthase complex in Salmonella newport. This protein spans 156 amino acids and functions as a peripheral stalk connecting the membrane-embedded F₀ sector with the catalytic F₁ sector. In Salmonella newport, atpF plays multiple essential roles:

The amino acid sequence of Salmonella newport atpF (MNLNATILGQAIAFILFVWFCMKYVWPPLMAAIEKRQKEIADGLASAERAHKDLDLAKASATDQLKKAKAEAQVIIEQANKRRAQILDEAKTEAEQERTKIVAQAQAEIEAERKRAREELRKQVAILAVAGAEKIIERSVDEAANSDIVDKLVAEL) reveals hydrophobic regions consistent with its membrane-associated function .

How does Salmonella newport atpF differ from ATP synthase subunit b in other bacterial species?

While ATP synthase subunit b maintains similar core functions across bacterial species, several notable differences exist in Salmonella newport atpF compared to other bacteria:

• Sequence variations: Salmonella newport atpF shows high homology (>90%) with other Salmonella species but less similarity with more distant genera

• Structural adaptations: Specific amino acid residues in Salmonella newport atpF may contribute to adaptation to different environmental niches

• Regulatory elements: The expression patterns and regulatory mechanisms of atpF in Salmonella newport show species-specific characteristics

• Immunological distinctions: The protein exhibits unique epitopes that can be exploited for detection and vaccine development

These differences make Salmonella newport atpF an interesting target for comparative studies on bacterial energy metabolism and adaptation strategies. Researchers should consider these species-specific differences when designing experiments or interpreting results from cross-species studies.

What are the key differences between recombinant atpF and native atpF from Salmonella newport?

Recombinant atpF protein differs from the native form in several important aspects that researchers should consider:

The recombinant version, though highly similar in primary structure, may exhibit differences in tertiary structure and functionality. The N-terminal His-tag facilitates purification but may impact protein-protein interactions in some experimental contexts. Researchers should validate that the recombinant protein maintains the biological properties relevant to their specific experiments .

What are the optimal conditions for reconstituting lyophilized recombinant Salmonella newport atpF protein for experimental use?

Proper reconstitution of lyophilized recombinant atpF is critical for maintaining protein integrity and functionality in experiments. Follow these methodological steps:

• Initial preparation: Centrifuge the vial briefly (30 seconds at 10,000g) to collect the powder at the bottom before opening.

• Reconstitution buffer selection: Use deionized sterile water to achieve a concentration of 0.1-1.0 mg/mL. For membrane proteins like atpF, consider adding mild detergents (0.1% DDM or 0.5% CHAPS) to maintain proper folding.

• Reconstitution procedure:

  • Add buffer slowly down the side of the tube

  • Gently rotate the vial until completely dissolved (avoid vortexing)

  • Allow 10-15 minutes at room temperature for complete hydration

• Long-term storage preparation: Add glycerol to a final concentration of 5-50% (with 50% being optimal) and aliquot into smaller volumes to avoid freeze-thaw cycles.

• Storage conditions: Store aliquots at -20°C or -80°C for long-term use, and working aliquots at 4°C for up to one week.

The reconstituted protein should maintain >90% of its activity when properly handled, though activity should be verified using appropriate assays specific to ATP synthase function .

How can researchers verify the structural integrity and functionality of recombinant Salmonella newport atpF after purification?

Verifying both structural integrity and functional activity of purified recombinant atpF requires a multi-method approach:

Structural integrity assessment:

• SDS-PAGE: Confirms the protein's molecular weight (should match the theoretical 156 amino acids plus tag)

• Western blotting: Using anti-His antibodies or atpF-specific antibodies to confirm identity

• Circular dichroism (CD): Evaluates secondary structure elements, particularly important for the alpha-helical regions of atpF

• Size exclusion chromatography: Assesses oligomeric state and aggregation

Functional assessment:

• ATP synthase reconstitution assays: Incorporating recombinant atpF into liposomes with other ATP synthase components

• Proton translocation assays: Measuring pH changes across membranes containing reconstituted ATP synthase

• ATP hydrolysis/synthesis assays: Quantifying enzymatic activity of reconstituted complexes

• Protein-protein interaction studies: Verifying binding to other ATP synthase subunits

Researchers should note that functional assessment requires reconstitution of atpF with other ATP synthase components, as the isolated subunit does not possess catalytic activity on its own. Proper folding can be assessed by comparing activity to native controls or previously validated recombinant preparations .

What approaches can be used to optimize expression of recombinant Salmonella newport atpF in E. coli systems?

Optimizing expression of recombinant atpF in E. coli requires careful consideration of several parameters:

Expression strain selection:

• BL21(DE3): Standard strain for high-level expression

• C41(DE3) or C43(DE3): Specialized for membrane protein expression

• Rosetta or Rosetta2: Helpful if atpF contains rare codons

Expression vector considerations:

• Low-copy number vectors (pACYC-derived) may reduce toxicity

• Inducible promoters (T7 or arabinose-inducible) for controlled expression

• Fusion tags beyond His (such as MBP or SUMO) may improve solubility

Culture conditions optimization:

• Temperature: Lower temperatures (16-25°C) often improve proper folding

• Induction timing: Induce at OD₆₀₀ of 0.6-0.8 for optimal balance

• Inducer concentration: Use lower IPTG concentrations (0.1-0.5 mM)

• Media supplementation: Consider adding membrane-stabilizing components

Extraction and purification strategies:

• Gentle lysis methods (enzymatic rather than sonication)

• Proper detergent selection (DDM, LDAO, or OG) for membrane extraction

• Gradient elution during purification to improve purity

By systematically optimizing these parameters, researchers can improve both yield and quality of recombinant atpF for downstream applications, potentially achieving expression levels of 5-10 mg/L culture with >90% purity .

How can recombinant Salmonella newport atpF be utilized in the development of Salmonella-based vaccines?

Recombinant atpF protein has significant potential in vaccine development strategies, particularly in the context of attenuated Salmonella vaccines:

As an antigenic component:

• The conserved regions of atpF can serve as targets for generating protective immune responses

• Fusion of atpF with other antigens may enhance immunogenicity

• Incorporation into outer membrane vesicles (OMVs) as delivery vehicles

As a genetic manipulation target:

• Introducing controlled mutations in chromosomal atpF can generate attenuated strains

• Using regulated atpF expression to create metabolic bottlenecks in vaccine strains

• Engineering atpF with altered functionality for controlled bacterial persistence

Implementation strategies:

• Identify immunogenic epitopes within atpF using epitope mapping

• Design constructs with optimized codon usage for expression in vaccine strains

• Create fusion proteins with immunostimulatory molecules

• Develop detection methods to track vaccine strain persistence and clearance

Researchers working with live attenuated Salmonella vaccines, such as the CVD 1979 strain (with deletions in guaBA, htrA, and aroA), could potentially incorporate atpF modifications to further refine vaccine characteristics including immunogenicity, persistence, and safety profiles .

What role does atpF play in Salmonella pathogenesis and survival in different environmental conditions?

The ATP synthase b subunit (atpF) contributes significantly to Salmonella pathogenesis and environmental adaptation through several mechanisms:

Acid stress survival:

• ATP synthase activity maintains intracellular pH homeostasis

• atpF function is crucial during gastric passage where Salmonella encounters extreme acidity

• Modulatory effects on proton concentration affect expression of virulence factors

Metabolic adaptation:

• Enables energy production under varying oxygen availability conditions

• Supports survival during nutrient limitation within host cells

• Contributes to rapid growth during infection establishment

Immune evasion strategies:

• Potential involvement in membrane potential maintenance affecting antimicrobial peptide resistance

• May influence outer membrane protein expression patterns

• Interacts with host-derived stress factors

Virulence regulation networks:

• Cross-talks with two-component regulatory systems in stress response

• Energetic status signaling affects virulence gene expression

• May participate in biofilm formation regulatory networks

These multifaceted roles make atpF an interesting target for studying both pathogenesis mechanisms and developing intervention strategies. Researchers investigating environmental adaptation could explore how atpF function varies across different Salmonella serovars to identify potential adaptation signatures .

How can structural analysis of atpF contribute to understanding ATP synthase assembly and function in Salmonella?

Structural analysis of atpF provides critical insights into ATP synthase assembly, stability, and functionality in Salmonella:

Key structural elements for investigation:

• N-terminal membrane-anchoring domain (residues 1-25)

• Central dimerization domain (residues 26-80)

• C-terminal domain interacting with F₁ sector (residues 81-156)

Advanced structural analysis approaches:

• Cryo-electron microscopy: Reveals atpF positioning within the intact ATP synthase complex

• X-ray crystallography: Provides atomic-level details of specific domains

• Hydrogen-deuterium exchange mass spectrometry: Identifies flexible regions and interaction interfaces

• Molecular dynamics simulations: Models conformational changes during ATP synthesis/hydrolysis

Structure-function relationships:

• Identifying critical residues for dimerization and stability

• Mapping interaction surfaces with other ATP synthase components

• Understanding species-specific structural adaptations

Translational applications:

• Design of specific inhibitors targeting Salmonella ATP synthase

• Engineering modified versions with altered stability or assembly properties

• Development of structure-based diagnostics

AlphaFold or similar protein structure prediction tools can serve as starting points for understanding atpF structure, but experimental validation through techniques like site-directed mutagenesis remains essential for confirming functional roles of specific structural elements .

How does Salmonella newport atpF compare with atpF proteins from other clinically relevant Salmonella serovars?

Comparative analysis of atpF across Salmonella serovars reveals important evolutionary patterns and functional implications:

Sequence conservation patterns:

• Core functional domains show >95% conservation across all Salmonella serovars

• Membrane-spanning regions exhibit highest sequence conservation

• Variable regions primarily cluster in solvent-exposed loops

• C-terminal F₁-interacting domain shows serovar-specific variations

Functional implications of variations:

• Subtle differences may affect ATP synthase efficiency under various environmental conditions

• Serovar-specific adaptations correlate with ecological niches and host ranges

• Variations in regulatory elements affect expression patterns during infection

Clinically relevant differences:

• S. Typhi atpF shows specific adaptations related to human-restricted lifestyle

• S. Typhimurium atpF contains modifications supporting broad host range

• S. Newport atpF exhibits characteristics reflective of its environmental persistence

These comparative insights help researchers understand the evolutionary pressures shaping ATP synthase function across different Salmonella lineages and may guide the development of serovar-specific interventions or diagnostic approaches .

What experimental approaches can resolve contradictory findings about atpF function in different research studies?

Resolving contradictory findings about atpF function requires systematic methodological approaches:

Sources of experimental discrepancies:

• Variation in recombinant protein preparation methods

• Differences in experimental conditions (pH, temperature, ionic strength)

• Strain-specific genetic backgrounds affecting phenotypes

• Incomplete reporting of methodological details

Resolution strategies:

• Standardized protocols:

  • Develop consistent expression and purification methodologies

  • Establish reference strains and constructs for community-wide use

  • Create shared repositories of validated reagents

• Multi-laboratory validation:

  • Conduct parallel experiments in different laboratories

  • Use multiple complementary techniques to assess the same parameter

  • Implement blinded analysis of experimental results

• Comprehensive controls:

  • Include positive and negative controls in all experiments

  • Test multiple atpF variants simultaneously

  • Create isogenic strains differing only in atpF sequence

• Systematic parameter variation:

  • Investigate environmental conditions systematically

  • Test response to varying stressors

  • Examine multiple genetic backgrounds

By implementing these approaches, researchers can resolve contradictions and develop a more unified understanding of atpF function across different experimental contexts and Salmonella serovars .

How might atpF modification be utilized in creating attenuated Salmonella strains for vaccine development?

Strategic modification of atpF offers promising approaches for vaccine development:

Attenuation strategies targeting atpF:

• Conditional expression systems (such as rhamnose-inducible promoters) controlling atpF expression

• Point mutations affecting efficiency without completely disrupting function

• Domain swapping with heterologous atpF sequences to create functional but attenuated variants

Benefits of atpF-based attenuation:

• Precise control over bacterial metabolism and growth

• Reduced risk of reversion compared to deletion mutants

• Tunable attenuation level for balancing safety and immunogenicity

Implementation approaches:

• Create genomic replacements using lambda red recombination similar to techniques used for other Salmonella attenuations

• Combine atpF modifications with established attenuating mutations (guaBA, htrA, aroA)

• Design conditional expression systems responding to environmental signals

Evaluation parameters:

• Growth kinetics in various media and conditions

• Persistence in animal models

• Immunogenicity and protective efficacy

• Genetic stability of modifications

This approach could complement existing Salmonella vaccine platforms like CVD 1979, which already incorporates deletions in guaBA, htrA, and aroA, by providing an additional attenuation mechanism targeting energy metabolism .

What potential does atpF have as a target for developing novel antimicrobials against multidrug-resistant Salmonella?

ATP synthase subunit b (atpF) represents a promising but challenging target for antimicrobial development:

Target validation evidence:

• Essential role in bacterial energy metabolism

• Structural differences from human ATP synthase components

• Limited redundancy in function

• Involvement in stress adaptation mechanisms

Antimicrobial development strategies:

• Small molecule inhibitors:

  • Target the dimerization interface of atpF

  • Disrupt interactions with other ATP synthase components

  • Interfere with proper membrane localization

• Peptide-based approaches:

  • Design competing peptides mimicking interaction domains

  • Develop cell-penetrating peptides targeting assembled ATP synthase

  • Create peptide-antibiotic conjugates for targeted delivery

• Combination approaches:

  • Identify synergistic effects with existing antibiotics

  • Target multiple ATP synthase components simultaneously

  • Combine with membrane permeabilizers for enhanced efficacy

Challenges and considerations:

• Developing selectivity for bacterial over mammalian ATP synthase

• Achieving sufficient penetration of the bacterial membrane

• Addressing potential resistance mechanisms

• Optimizing pharmacokinetic properties

Researchers pursuing this direction should implement target validation studies, develop high-throughput screening assays specific for atpF function, and establish appropriate in vitro and in vivo models for evaluating efficacy against multidrug-resistant Salmonella strains .

What are the most significant recent advances in understanding Salmonella newport atpF and its applications in research?

Recent advances in Salmonella newport atpF research have expanded our understanding of this protein's structural properties, functional roles, and potential applications:

Structural insights:

• Improved structural models through computational approaches like AlphaFold

• Better understanding of interaction interfaces with other ATP synthase components

• Identification of critical residues for function through mutational analyses

Functional characterization:

• Elucidation of roles beyond energy production, including stress response

• Understanding of atpF contribution to bacterial persistence in hostile environments

• Recognition of potential involvement in virulence regulation networks

Methodological improvements:

• Enhanced recombinant protein expression and purification protocols

• Development of activity assays specific for atpF function

• Improved in vitro reconstitution systems for ATP synthase complexes

Translational applications:

• Progress in utilizing atpF in vaccine development strategies

• Exploration as a potential antimicrobial target

• Use as a model system for understanding membrane protein complexes

These advances collectively provide researchers with better tools and deeper insights for investigating both fundamental aspects of bacterial bioenergetics and applied topics in bacterial pathogenesis and intervention strategies .

What are the major limitations in current atpF research methodologies and how might they be addressed?

Current research on Salmonella newport atpF faces several methodological limitations that require innovative solutions:

Current limitations:

• Membrane protein challenges:

  • Difficulties in obtaining sufficient quantities of properly folded protein

  • Limited stability outside native membrane environment

  • Challenges in structural analysis of membrane-embedded domains

• Functional assessment constraints:

  • Need for complex reconstitution systems to measure activity

  • Difficulty isolating atpF-specific effects from whole ATP synthase function

  • Limited availability of high-throughput screening approaches

• Translational research barriers:

  • Gap between in vitro findings and in vivo relevance

  • Challenges in developing atpF-specific tools for clinical applications

  • Limited animal models for studying atpF-specific phenomena

Innovative solutions:

• Advanced expression systems:

  • Cell-free protein synthesis optimized for membrane proteins

  • Nanodiscs and other membrane mimetics for improved stability

  • Engineering fusion constructs to enhance folding and solubility

• New analytical approaches:

  • Single-molecule techniques for studying dynamics

  • Native mass spectrometry for intact complex analysis

  • Advanced microscopy methods for visualizing ATP synthase assembly

• Integrative research frameworks:

  • Combining structural, functional, and -omics approaches

  • Developing mathematical models of ATP synthase function

  • Establishing collaborative networks to address multidisciplinary challenges