Recombinant Salmonella enteritidis PT4 Bifunctional protein aas (aas)

What is the Salmonella enteritidis PT4 Bifunctional protein aas?

The bifunctional protein aas in Salmonella enteritidis PT4 (strain P125109) is a 719 amino acid protein encoded by the aas gene (locus SEN2853). It functions as a 2-acylglycerophosphoethanolamine acyltransferase (EC 2.3.1.40), also known as 2-acyl-GPE acyltransferase. This enzyme participates in phospholipid metabolism, specifically in the transfer of acyl groups from acyl-carrier proteins to phospholipids . The protein contains multiple functional domains that contribute to its enzymatic activities in bacterial membrane lipid homeostasis.

How does the expression of bifunctional protein aas differ between planktonic and biofilm growth conditions?

While the search results don't specifically address the expression of bifunctional protein aas in different growth conditions, research on S. Enteritidis PT4 has shown significant differences in protein expression between planktonic and biofilm growth states. In a proteomics study, 30 proteins were differentially expressed on an "on-off" basis between biofilm and planktonic growth modes, with 20 proteins detected only in biofilm cells and 10 proteins only in planktonic cells .

These differentially expressed proteins included those involved in global regulation, stress response, nutrient transport, energy metabolism, and detoxification. Though bifunctional protein aas was not specifically mentioned in the differentially expressed proteins, this research paradigm demonstrates how growth conditions can substantially alter protein expression profiles in Salmonella enteritidis PT4.

What are the optimal conditions for expressing and purifying recombinant Salmonella enteritidis PT4 bifunctional protein aas?

The optimal expression and purification of recombinant bifunctional protein aas requires careful consideration of several factors. Based on standard protocols for similar bacterial proteins:

Expression System Selection:

• Prokaryotic systems (E. coli BL21(DE3) or similar strains) are typically preferred for bacterial protein expression

• Vector selection should incorporate appropriate promoters (T7, tac) and affinity tags (His, GST) for efficient purification

Expression Conditions:

Purification Strategy:

• Cell lysis using sonication or pressure-based methods in buffers containing 20-50 mM Tris-HCl (pH 7.5-8.0), 100-300 mM NaCl

• Addition of glycerol (10-20%) and reducing agents may improve stability

• Affinity chromatography based on the incorporated tag

• Size exclusion chromatography for higher purity

• Storage in Tris-based buffer with 50% glycerol at -20°C or -80°C for extended periods

The recombinant protein is typically stored in a Tris-based buffer with 50% glycerol to maintain stability. Repeated freeze-thaw cycles should be avoided, and working aliquots can be stored at 4°C for up to one week .

How does the bifunctional protein aas contribute to Salmonella pathogenicity and host adaptation?

Research has shown that S. Enteritidis PT4 and S. Typhimurium LT2 share >90% of their coding sequences, forming an extensive core gene set with an average nucleotide identity of 98.98% . These core genes, which likely include the aas gene, contribute to the basic cellular functions and potentially to pathogenicity.

S. Enteritidis PT4 harbors multiple functional fimbrial operons that play roles in host colonization and virulence . While the bifunctional protein aas is not directly mentioned as a virulence factor, proteins involved in membrane lipid metabolism often contribute to bacterial adaptation to host environments by:

• Maintaining membrane integrity under stress conditions

• Contributing to biofilm formation capabilities

• Potentially modifying surface structures to evade host immunity

• Supporting bacterial survival under nutrient-limited conditions

The genomic analysis of host-adapted Salmonella strains has revealed that gene degradation through deletion and pseudogene formation is a common mechanism of host adaptation . The preservation of functional aas in S. Enteritidis PT4 suggests its importance for the bacterium's lifecycle and potentially for its pathogenic capabilities.

What are the challenges in developing antibodies against the bifunctional protein aas for detection and research applications?

Developing antibodies against the bifunctional protein aas presents several technical challenges:

Antigenicity Considerations:

• The protein's hydrophobic regions may be poorly immunogenic

• Conserved domains shared with host proteins could lead to cross-reactivity

• Protein folding in the recombinant form may differ from native conformation

Production Challenges:

Validation Requirements:

• Western blot analysis against both recombinant and native protein

• Immunoprecipitation to confirm recognition of the native protein

• Immunofluorescence to verify antibody utility in localization studies

• Testing against related bacterial species to confirm specificity

For detection applications, phage-based approaches may provide alternatives to antibody-based methods. Research has demonstrated the use of phage tail fiber proteins for specific detection of Salmonella enterica, which could be adapted for targeting specific proteins .

What techniques are most effective for studying the enzymatic activity of bifunctional protein aas?

The enzymatic activity of bifunctional protein aas can be studied using several complementary approaches:

In Vitro Enzymatic Assays:

• Acyltransferase Activity Measurement:

  • Radiometric assays using 14C-labeled acyl-CoA or acyl-ACP substrates

  • HPLC-based assays measuring substrate depletion and product formation

  • Colorimetric assays using modified substrates that release detectable products

• Kinetic Analysis:

  • Determination of Km and Vmax values for various substrates

  • Inhibition studies to characterize active site properties

  • pH and temperature optimization

Structural Studies:

• X-ray crystallography of purified protein to determine three-dimensional structure

• NMR spectroscopy for dynamic structural information

• Site-directed mutagenesis of predicted catalytic residues followed by activity assays

In Vivo Functional Studies:

• Gene knockout or knockdown studies in Salmonella

• Complementation assays in mutant strains

• Metabolic labeling to trace phospholipid modifications in living bacteria

For the 2-acylglycerophosphoethanolamine acyltransferase activity, specific assays measuring the transfer of acyl groups from acyl carrier proteins to phospholipids would be particularly relevant. These could be designed using fluorescent or radioisotope-labeled substrates to track the movement of acyl groups.

How can genomic and proteomic approaches be integrated to understand the role of bifunctional protein aas in Salmonella biology?

Integrating genomic and proteomic approaches provides a comprehensive understanding of bifunctional protein aas function:

Multi-omics Integration Strategy:

• Genomic Analysis:

  • Comparative genomics across Salmonella strains to identify conservation patterns and genetic context of the aas gene

  • Identification of regulatory elements controlling aas expression

  • Analysis of single nucleotide polymorphisms or other variations that might affect protein function

• Transcriptomic Studies:

  • RNA-seq to determine expression patterns under different conditions

  • Identification of co-expressed genes to infer functional relationships

  • Analysis of regulatory networks controlling aas expression

• Proteomic Approaches:

  • 2D-PAGE and MALDI-TOF mass spectrometry to identify differential protein expression, as demonstrated in the planktonic versus biofilm growth study

  • Protein-protein interaction studies (pull-down assays, yeast two-hybrid) to identify functional partners

  • Post-translational modification analysis to identify regulatory mechanisms

• Metabolomic Studies:

  • Phospholipid profiling to identify changes in membrane composition

  • Metabolic flux analysis to understand the impact of aas function on cellular metabolism

Integration Framework:

The study of S. Enteritidis protein expression in biofilm versus planktonic growth demonstrates the value of proteomic approaches in understanding bacterial adaptation . Similar approaches could be applied specifically to understand the role of bifunctional protein aas in different growth conditions and stress responses.

How can recombinant bifunctional protein aas be utilized in developing detection methods for Salmonella enteritidis?

Recombinant bifunctional protein aas offers several avenues for developing Salmonella detection methods:

Antibody-Based Detection:

• Generation of monoclonal or polyclonal antibodies against unique epitopes

• Development of ELISA-based detection systems using these antibodies

• Lateral flow immunoassays for rapid field detection

• Immunomagnetic separation combined with other detection methods

Biosensor Development:

• Using the recombinant protein to select aptamers with high binding affinity

• Development of magnetoresistive biosensors similar to those described for phage-based detection systems

• Surface plasmon resonance (SPR) or quartz crystal microbalance (QCM) sensors using immobilized antibodies

Phage-Based Detection Systems:
Research has demonstrated the potential of phage-derived recognition elements for Salmonella detection. Similar approaches could be adapted to target the bifunctional protein aas:

• Selection of phages or phage display peptides that specifically bind to exposed regions of the protein

• Development of recognition peptides similar to the "tail fibre proteins of phage PVP-SE1" that showed "equal binding affinities compared to their parental phage"

• Integration with magnetoresistive sensors for highly sensitive detection systems

The advantage of these approaches is their ability to potentially distinguish between viable and non-viable states of bacteria, including the viable but non-culturable (VBNC) state that poses significant detection challenges in food safety and clinical diagnostics .

What insights can be gained from studying the bifunctional protein aas regarding Salmonella adaptation to different environmental conditions?

Studying the bifunctional protein aas can provide valuable insights into Salmonella adaptation mechanisms:

Membrane Adaptation Insights:

• Changes in phospholipid metabolism may reflect adaptation to varying temperatures, pH, or osmotic conditions

• Modifications in membrane composition could contribute to antimicrobial resistance

• Altered expression or activity of aas may correlate with biofilm formation capability

Evolutionary Perspectives:
Comparative genomic studies between S. Enteritidis PT4 and other Salmonella strains show that while they share extensive core gene sets, specific adaptations occur through gene acquisition, loss, or modification . Analysis of the aas gene across different Salmonella lineages could reveal:

• Conservation patterns indicating functional importance

• Variations correlating with host specificity or niche adaptation

• Changes in expression regulation reflecting environmental adaptation

Host-Pathogen Interaction:
Research has shown that S. Gallinarum 287/91 is likely a recently evolved descendant of S. Enteritidis that has undergone extensive genome degradation through deletion and pseudogene formation, leading to host adaptation . Studying if and how aas function differs between these strains could provide insights into:

• The role of membrane phospholipid composition in host specificity

• Potential contributions to tissue tropism within hosts

• Involvement in survival within host immune environments

The study of proteins differentially expressed during biofilm versus planktonic growth demonstrates how growth conditions affect Salmonella's protein expression patterns . Similar approaches focused specifically on aas expression and activity under different conditions would contribute to understanding its role in environmental adaptation.

What are the emerging techniques for studying the structure-function relationship of bifunctional protein aas?

Several cutting-edge techniques show promise for elucidating the structure-function relationship of bifunctional protein aas:

Advanced Structural Biology Approaches:

• Cryo-electron microscopy (Cryo-EM) for high-resolution structural determination without crystallization

• Integrative structural biology combining multiple techniques (X-ray crystallography, NMR, SAXS, molecular dynamics)

• Hydrogen-deuterium exchange mass spectrometry (HDX-MS) to map protein dynamics and ligand interactions

• AlphaFold2 and related AI-based structure prediction to model protein structure and dynamic states

Functional Characterization:

• CRISPR-Cas9 genome editing for precise manipulation of the aas gene in its native context

• Single-molecule enzymology to observe individual catalytic events and conformational changes

• Microfluidic platforms for high-throughput screening of substrate specificity and inhibitors

• Synthetic biology approaches to create chimeric proteins or minimal functional domains

Integration with Systems Biology:

These emerging techniques could help resolve unanswered questions about the bifunctional nature of the protein, the coordination between its different enzymatic activities, and its regulation under different environmental conditions.

How might understanding the bifunctional protein aas contribute to novel antimicrobial strategies against Salmonella infections?

Understanding the bifunctional protein aas could inform novel antimicrobial approaches through several mechanisms:

Target-Based Drug Design:

• Structural characterization of the active sites to design specific inhibitors

• Identification of allosteric sites that could modulate enzyme activity

• Design of molecules that disrupt essential protein-protein interactions

• Development of prodrugs activated by the enzymatic activity of aas

Membrane-Targeting Strategies:

• Design of antimicrobials that synergize with disruptions in phospholipid metabolism

• Development of compounds that alter membrane fluidity or permeability in aas-compromised bacteria

• Creation of delivery systems that exploit aas-dependent membrane properties

Immunological Approaches:

• Identification of exposed epitopes for vaccine development

• Understanding of how aas-mediated membrane modifications affect immune recognition

• Development of antibody-antibiotic conjugates targeting surface-exposed regions of the protein

Research has demonstrated that biofilm formation in S. Enteritidis involves distinct changes in protein expression . If aas plays a role in biofilm formation or maintenance, targeting its function could potentially disrupt this important virulence mechanism. Similarly, the use of phage-derived recognition elements has shown promise for Salmonella detection , and this approach could potentially be adapted for therapeutic delivery of antimicrobials specifically to Salmonella cells.