Recombinant Salmonella paratyphi A Bifunctional protein aas (aas)

What is the Bifunctional protein aas in Salmonella paratyphi A and what are its key structural features?

The Bifunctional protein aas in Salmonella paratyphi A is a 719-amino acid protein that likely functions in membrane phospholipid metabolism. Based on its designation as "bifunctional," it presumably has dual enzymatic activities, potentially including acyltransferase and acyl-ACP synthetase functions, which are critical for bacterial membrane maintenance .

The protein can be recombinantly expressed with an N-terminal His tag in E. coli and has the following structural characteristics:

The sequence begins with MLFGFFRNLFRVLYRVRV and contains multiple functional domains that contribute to its dual enzymatic activities .

How conserved is the aas gene across different Salmonella strains?

Comparison of the aas protein sequences from S. paratyphi A and S. paratyphi B reveals high conservation, suggesting evolutionary importance. Both proteins contain 719 amino acids with identical N-terminal sequences, indicating strong selective pressure to maintain this protein's function .

Notable differences include amino acid substitutions such as:

• S. paratyphi A: ...RETLYESLLAAQYRYGAGK...

• S. paratyphi B: ...RETLYESLLVAQYRYGAGK...

This level of conservation is consistent with patterns observed in other Salmonella genes. For example, S. paratyphi A flagellin genes show high sequence conservation, with similarities from 99.31 to 99.88% across isolates . Similarly, the spaO gene has shown 97.5% distribution across 196 S. paratyphi A isolates with high conservation .

What expression systems are optimal for producing recombinant Salmonella paratyphi A Bifunctional protein aas?

E. coli has been successfully used as an expression system for recombinant production of Bifunctional protein aas from both S. paratyphi A and B . The methodology typically involves:

• Cloning the full-length aas gene (1-719aa) into an expression vector with an N-terminal His tag

• Transforming into E. coli expression strains

• Inducing protein expression under optimized conditions

• Purifying via affinity chromatography

For researchers working with similar Salmonella proteins, expression parameters can be adapted from successful approaches used with other S. paratyphi A proteins. For example, when expressing the flagellin protein of S. paratyphi A, researchers successfully used PCR techniques to establish an expression plasmid (pSKA-7) that produced a 33.5 kDa recombinant protein .

What are the recommended storage conditions for maintaining stability of recombinant Bifunctional protein aas?

The stability of recombinant Bifunctional protein aas is optimized under the following conditions :

The protein is typically supplied in a Tris/PBS-based buffer with 6% Trehalose at pH 8.0, which contributes to stability .

What techniques can improve the purity and activity of recombinant Bifunctional protein aas?

A multi-step purification strategy is recommended to achieve high purity and activity:

• Initial capture using immobilized metal affinity chromatography (IMAC) leveraging the N-terminal His tag

• Assessment of purity by SDS-PAGE (target: >90%)

• Optional secondary purification steps such as ion exchange or size exclusion chromatography for enhanced purity

• Buffer optimization to maintain protein stability and native conformation

When working with recombinant S. paratyphi A proteins, maintaining a cold chain throughout purification is critical. For example, in studies with outer membrane proteins from S. paratyphi A, temperature control was essential for preserving immunogenicity of the purified components .

What are the presumed enzymatic functions of the Bifunctional protein aas and how might they be characterized?

Based on its classification as a bifunctional protein and sequence analysis, the aas protein likely possesses dual enzymatic activities:

Enzymatic characterization would typically involve:

• Substrate specificity analysis using various fatty acids and acceptor molecules

• Kinetic measurements (Km, Vmax, kcat) for both activities

• Effect of pH, temperature, and ionic conditions on activity

• Inhibition studies with potential competitive inhibitors

Similar enzymatic characterization approaches have been successfully applied to other S. paratyphi A proteins, such as the type III secretion system proteins .

How does the His-tag affect the structure and function of the recombinant Bifunctional protein aas?

While specific data on the effect of the His-tag on this particular protein isn't available, methodological considerations include:

• Potential impacts of the N-terminal His-tag:

  • May affect protein folding, especially if located near catalytic domains

  • Could potentially interfere with enzymatic activity if near active sites

  • May influence protein-protein interactions if the protein functions as a multimer

• Experimental approaches to assess tag effects:

  • Comparing enzymatic activities of tagged vs. untagged versions

  • Structural studies with and without the tag

  • Tag removal using specific proteases (e.g., TEV protease) if needed for functional studies

When working with similar recombinant proteins from S. paratyphi A, researchers have observed that tag position and composition can affect antigenicity and recognition by immune sera .

What potential role might the Bifunctional protein aas play in Salmonella paratyphi A virulence?

While direct evidence for the role of aas in virulence isn't available in the search results, its presumed function in membrane phospholipid metabolism suggests several potential contributions to pathogenesis:

• Membrane integrity maintenance: S. paratyphi A must survive harsh environments during infection, including stomach acid and host defense mechanisms. Proper membrane function is critical for this survival .

• Adaptation to host environments: During infection, S. paratyphi A progresses from the intestinal epithelium to systemic sites including lymphoid tissue, mesenteric lymph nodes, bloodstream, and eventually phagocytes in the spleen, liver, and bone marrow . These transitions likely require membrane remodeling.

• Potential contribution to outer membrane vesicle (OMV) formation: OMVs are important for delivering virulence factors, and membrane composition affects their production. Research has shown that disruption of membrane proteins (e.g., tolR knockout) increases vesicle formation in Salmonella strains .

The importance of membrane components in S. paratyphi A virulence is supported by research showing that outer membrane proteins like LamB, PagC, TolC, NmpC, and FadL demonstrate significant immunoprotection in mice, with protection rates of 95, 95, 85, 80, and 70%, respectively .

Could the Bifunctional protein aas serve as a potential vaccine target or diagnostic marker?

The potential of the Bifunctional protein aas as a vaccine target or diagnostic marker can be evaluated based on similar approaches with other S. paratyphi A proteins:

Research has shown that proteins located in the outer membrane or involved in membrane functions can be effective vaccine candidates. For example, immunization with five different outer membrane proteins from S. paratyphi A conferred significant protection in mouse models . The conservation of the aas gene across strains suggests it could potentially serve as a stable diagnostic target.

How could CRISPR-Cas9 or similar gene editing technologies be applied to study the function of the aas gene?

CRISPR-Cas9 technology offers several sophisticated approaches to investigate the aas gene function:

• Gene knockout studies:

  • Complete deletion of the aas gene to create null mutants

  • Assessment of phenotypic effects on growth, membrane composition, and virulence

  • Complementation studies to confirm specificity of observed effects

• Domain-specific modifications:

  • Targeted mutations in specific functional domains to separate the dual enzymatic activities

  • Creation of point mutations in predicted catalytic residues to selectively inactivate either function

  • Structure-function relationship studies through precise genetic edits

• Regulated expression systems:

  • Integration of inducible promoters to control aas expression levels

  • Creation of temperature-sensitive variants for conditional expression studies

  • Development of reporter fusions to study gene expression under various conditions

Similar genetic manipulation approaches have been successfully applied to other Salmonella genes. For example, researchers deleted guaBA and clpX from S. paratyphi A ATCC 9150 to create attenuated mutants for vaccine development , and tolR knockouts were created to increase vesicle formation for immunization studies .

What comparative genomic approaches could reveal about the evolution of the aas gene across Salmonella species?

Comparative genomic analysis of the aas gene could provide valuable evolutionary insights:

This approach is supported by previous comparative genomic studies on Salmonella. For instance, research has shown that "S. paratyphi C has diverged from a common ancestor with S. choleraesuis by accumulating genomic novelty during adaptation to man" . Similar adaptive processes might have shaped the aas gene across different Salmonella serovars.

How might metabolomic approaches help understand the role of Bifunctional protein aas in Salmonella metabolism?

Metabolomic analysis can provide insights into the role of the aas protein in Salmonella metabolism:

• Comparative metabolomics:

  • Profiling metabolite differences between wild-type and aas-deficient strains

  • Identifying alterations in phospholipid composition and fatty acid metabolism

  • Detecting metabolic bottlenecks created by aas mutation

• Flux analysis:

  • Tracing carbon flow through metabolic pathways using labeled substrates

  • Determining how aas affects flux distribution in phospholipid biosynthesis

  • Measuring quantitative changes in membrane lipid turnover rates

• Host-pathogen metabolic interaction:

  • Investigating how aas function affects adaptation to host metabolic environments

  • Identifying metabolic signatures associated with aas activity during infection

  • Correlating metabolic profiles with virulence phenotypes

The feasibility of this approach is supported by research showing that metabolomic analysis can distinguish S. Typhi from S. Paratyphi A infections based on their distinct metabolite profiles . The study identified 695 individual metabolite peaks and found "highly significant and reproducible metabolite profiles separating S. Typhi cases, S. Paratyphi A cases, and controls" .

How does the Bifunctional protein aas from S. paratyphi A compare with homologs in other Salmonella serovars?

Comparative analysis of the Bifunctional protein aas sequences from S. paratyphi A and S. paratyphi B reveals:

The observed pattern of high conservation with specific amino acid substitutions suggests:

• Essential core functions maintained across serovars

• Subtle functional adaptations potentially related to host specificity or metabolic differences

• Regions under different selective pressures that might correlate with pathogenic traits

This pattern resembles what has been observed with other Salmonella proteins. For example, the flagellin gene of S. paratyphi A shows conserved terminal regions but a variable central region that confers specificity .

What approaches can be used to develop inhibitors targeting the Bifunctional protein aas?

Development of specific inhibitors targeting the Bifunctional protein aas would follow these research stages:

• Target validation:

  • Confirmation of essentiality or importance for virulence through gene knockout studies

  • Demonstration of unique features distinct from host enzymes

  • Assessment of conservation across clinical isolates to ensure broad-spectrum activity

• Inhibitor development strategies:

  • Structure-based drug design utilizing crystal structures or homology models

  • High-throughput screening of compound libraries against purified protein

  • Fragment-based approaches to identify building blocks for inhibitor design

  • Rational design of substrate analogs or transition state mimics

• Validation and optimization:

  • Enzymatic assays to confirm mechanism of action and potency

  • Cellular assays to verify penetration and activity in intact bacteria

  • Structure-activity relationship studies to improve potency and selectivity

  • Assessment of resistance development potential

Similar approaches have been successful with other Salmonella enzymes and virulence factors. Given the potential role of aas in membrane metabolism, inhibitors might disrupt bacterial adaptability during infection, similar to how mutations in other metabolic genes (guaB and guaA) attenuate virulence .