Recombinant Salmonella schwarzengrund UPF0756 membrane protein YeaL (yeaL)

How is the recombinant YeaL protein typically expressed and purified?

The recombinant YeaL protein is typically expressed in E. coli expression systems, which provide an efficient platform for producing bacterial membrane proteins. The general methodology involves:

• Cloning: The yeaL gene (UniProt ID: B4TU95) is cloned into an expression vector that contains an N-terminal His-tag sequence.

• Expression: The construct is transformed into E. coli cells and protein expression is induced under optimized conditions.

• Extraction: As a membrane protein, extraction requires careful solubilization using detergents that preserve the protein's native conformation.

• Purification: The His-tagged protein is purified using nickel affinity chromatography, exploiting the high affinity of the His-tag for Ni²⁺ ions.

• Quality control: The purified protein undergoes SDS-PAGE analysis to confirm purity (typically >90%).

• Lyophilization: The purified protein is lyophilized to form a powder, which improves stability for storage .

For optimal results, researchers should reconstitute the lyophilized protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL and add glycerol (5-50% final concentration) before aliquoting for long-term storage at -20°C/-80°C .

What is the predicted membrane topology of YeaL protein?

While specific experimental data on YeaL topology is limited in the available literature, computational analysis of the amino acid sequence suggests a multi-pass transmembrane protein structure. The sequence "MFDVTLLILLGLAALGFISHNTTVAVSILVLIIVRVTPLNTFFPWIEKQGLTVGIIILTIGVMAPIASGTLPPSTLIHSFVNWKSLVAIAVGVFVSWLGGRGITLMGNQPQLVAGLLVGTVLGVALFRGVPVGPLIAAGLVSLIVGKQ" contains several hydrophobic stretches typical of transmembrane domains.

The protein likely contains:

• 3-4 transmembrane helices

• Short hydrophilic loops connecting the transmembrane segments

• N-terminal and C-terminal domains with different cellular localizations

To experimentally confirm this topology, researchers typically employ:

• Protease accessibility assays

• Cysteine scanning mutagenesis coupled with accessibility studies

• Fusion reporter systems (such as PhoA or GFP)

• Epitope tagging at predicted loop regions followed by immunofluorescence microscopy

Understanding the membrane topology is crucial for functional studies as it determines which portions of the protein interact with the extracellular environment versus the cytoplasm .

What are the optimal storage conditions for recombinant YeaL protein?

The optimal storage conditions for recombinant Salmonella schwarzengrund UPF0756 membrane protein YeaL are crucial for maintaining its structural integrity and biological activity. Based on the manufacturer's recommendations, the following protocol should be followed:

• Short-term storage: Working aliquots can be stored at 4°C for up to one week.

• Long-term storage: Store the lyophilized powder at -20°C/-80°C upon receipt.

• Reconstitution protocol:

  • Briefly centrifuge the vial before opening to ensure all material is at the bottom

  • Reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL

  • Add glycerol to a final concentration of 5-50% (with 50% being optimal)

  • Prepare multiple aliquots to avoid repeated freeze-thaw cycles

• Buffer conditions: The protein is typically supplied in a Tris/PBS-based buffer with 6% Trehalose at pH 8.0, which helps maintain stability.

It's important to note that repeated freezing and thawing significantly reduces protein integrity and should be avoided. Instead, prepare smaller working aliquots during the initial reconstitution. The presence of trehalose in the storage buffer provides cryoprotection by preventing protein denaturation during freeze-thaw cycles .

How can I validate the activity of recombinant YeaL protein in experimental settings?

Validating the activity of recombinant YeaL protein requires multiple complementary approaches since its specific function remains incompletely characterized. The following methodological workflow is recommended:

• Structural integrity assessment:

  • SDS-PAGE analysis to confirm correct molecular weight (~16 kDa plus tag size)

  • Circular dichroism spectroscopy to verify secondary structure elements

  • Limited proteolysis to assess proper folding

• Membrane incorporation assays:

  • Liposome reconstitution experiments

  • Detergent solubility profiling

  • Blue native PAGE to assess oligomeric state

• Binding studies:

  • Pull-down assays to identify potential binding partners

  • Surface plasmon resonance (SPR) to quantify interaction kinetics

  • Isothermal titration calorimetry (ITC) for thermodynamic binding parameters

• Functional assays (based on comparative analyses with other bacterial membrane proteins):

  • Membrane permeability assays

  • Assessment of ion flux in reconstituted proteoliposomes

  • Bacterial complementation studies using yeaL-deficient strains

• Immunological activity validation:

  • T-cell proliferation assays, similar to those described for OmpA

  • Cytokine production measurement following exposure to immune cells

  • Assessment of antibody recognition using sera from infected hosts

The selection of appropriate validation methods should be guided by experimental hypotheses about YeaL's function, drawing parallels with better-characterized bacterial membrane proteins like OmpA and OmpD .

What methodological approaches are recommended for studying protein-protein interactions involving YeaL?

To effectively study protein-protein interactions involving YeaL, researchers should employ multiple complementary techniques that account for its membrane-embedded nature. The following methodological approach is recommended:

• Co-immunoprecipitation (Co-IP) with membrane-specific modifications:

  • Use mild detergents (DDM, CHAPS, or digitonin) for solubilization

  • Employ anti-His antibodies to pull down YeaL complexes

  • Analyze by mass spectrometry to identify binding partners

  • Validate findings with reciprocal Co-IP experiments

• Membrane-based yeast two-hybrid systems:

  • MYTH (Membrane Yeast Two-Hybrid) system

  • Split-ubiquitin yeast two-hybrid assay

  • These systems are specifically designed for membrane proteins

• Proximity-based labeling techniques:

  • BioID or TurboID fusions to YeaL for in vivo proximity labeling

  • APEX2-based proximity labeling

  • These methods can identify transient or weak interactors

• Microscopy-based interaction studies:

  • Fluorescence Resonance Energy Transfer (FRET)

  • Bimolecular Fluorescence Complementation (BiFC)

  • Super-resolution microscopy to visualize interaction domains

• Crosslinking mass spectrometry (XL-MS):

  • Chemical crosslinking followed by MS analysis

  • Particularly useful for capturing transient interactions

  • Can provide structural information about interaction interfaces

A multi-technique approach is essential as each method has inherent limitations when applied to membrane proteins. For instance, techniques requiring extensive washing may disrupt weak but physiologically relevant interactions. Control experiments with mutant versions of YeaL should be conducted to validate specificity of observed interactions .

What is the role of membrane proteins like YeaL in Salmonella pathogenesis?

Membrane proteins play crucial roles in Salmonella pathogenesis, serving as interfaces between the bacterium and its environment. While the specific role of YeaL has not been fully characterized in the provided search results, we can draw insights from studies of other Salmonella membrane proteins:

• Environmental sensing and adaptation: Membrane proteins often function as sensors that detect environmental changes, including pH shifts. This is particularly relevant as Salmonella encounters acidic stress in the stomach and within macrophage phagosomes. Similar to the acid-induced phenotype (AIP) associated with the FliC protein, YeaL might participate in acid response mechanisms .

• Host-pathogen interactions: Outer membrane proteins of Salmonella serve as pathogen-associated molecular patterns (PAMPs) that interact with host immune receptors. Studies with OmpA showed that it stimulates proinflammatory cytokine production and elicits T-cell responses in synovial fluid of patients with reactive arthritis .

• Virulence regulation: Some membrane proteins modulate virulence by influencing signaling pathways. For instance, IgaA has been shown to contribute to virulence by repressing the RcsC-YojN-RcsB phosphorelay system in host tissues and attenuating intracellular growth in fibroblasts .

• Immune evasion and survival: Membrane proteins can contribute to bacterial survival within host cells by modifying the intracellular compartment or resisting antimicrobial peptides.

• Adhesion and invasion: Several outer membrane proteins facilitate attachment to and invasion of host cells.

To investigate YeaL's specific role in pathogenesis, researchers should consider:

• Creating yeaL deletion mutants and assessing virulence in cell culture and animal models

• Evaluating protein expression levels under various infection-relevant conditions

• Examining interactions with host proteins using pull-down assays

• Analyzing immune responses to purified YeaL protein

How might YeaL contribute to Salmonella schwarzengrund virulence compared to other Salmonella strains?

Understanding the potential contribution of YeaL to Salmonella schwarzengrund virulence requires a comparative approach that considers both protein sequence conservation and the epidemiological context of this particular serovar:

• Sequence conservation analysis:

  • Perform multiple sequence alignments of YeaL homologs across Salmonella serovars

  • Identify schwarzengrund-specific variations that might affect protein function

  • Map these variations onto predicted functional domains

• Expression pattern differences:

  • Compare yeaL expression levels between S. schwarzengrund and other serovars under various infection-relevant conditions (acid stress, macrophage infection, etc.)

  • Analyze transcriptomic data for co-expression patterns with known virulence factors

• Serovar-specific interactions:

  • Investigate if YeaL from S. schwarzengrund interacts with unique partner proteins

  • Examine if its membrane localization differs from homologs in other serovars

• Epidemiological context:

  • S. schwarzengrund has been associated with specific infection patterns and outbreaks

  • Some Salmonella serovars, like the S. enterica subsp. II serovar 4,5,12:a:- described in search result , can cause clusters of infection despite being previously considered rare in humans

  • Similarly, YeaL might contribute to specific adaptation strategies in S. schwarzengrund

• Comparative virulence studies:

  • Generate isogenic mutants lacking yeaL in multiple Salmonella serovars

  • Compare phenotypes in cellular and animal infection models

  • Evaluate competitive indices between wild-type and mutant strains

In the absence of direct experimental data on YeaL's role in S. schwarzengrund specifically, researchers should adapt methodologies used to study other membrane proteins like OmpA and IgaA, which have established roles in pathogenesis. Techniques such as whole-genome sequencing and comparative genomics can reveal evolutionary patterns that might indicate serovar-specific adaptations in YeaL structure or function .

What experimental methods can be used to assess YeaL's potential role in bacterial stress response?

Assessing YeaL's potential role in bacterial stress response requires a systematic approach that combines genetic, physiological, and biochemical methods. The following experimental framework is recommended:

• Genetic manipulation strategies:

  • Generate a clean deletion mutant (ΔyeaL) in Salmonella schwarzengrund

  • Create complemented strains expressing wild-type yeaL from a plasmid

  • Develop conditional expression systems for controlled yeaL expression

  • Construct reporter fusions (yeaL-gfp, yeaL-lux) to monitor expression

• Stress exposure and phenotypic characterization:

  • Expose wild-type and ΔyeaL strains to various stresses relevant to Salmonella's lifecycle:

    • Acid stress (pH 3.0-5.0) mimicking stomach conditions

    • Oxidative stress (H₂O₂, paraquat)

    • Antimicrobial peptides resembling host defense molecules

    • Bile salts encountered in the intestine

    • Osmotic stress with varying NaCl concentrations

    • Temperature shifts (cold shock, heat shock)

  • Measure survival rates, growth kinetics, and morphological changes

• Transcriptional response analysis:

  • Perform RNA-Seq comparing wild-type and ΔyeaL strains under stress conditions

  • Quantify yeaL expression using qRT-PCR across stress conditions

  • Use promoter-reporter fusions to identify stress-responsive regulatory elements

• Protein interaction studies during stress:

  • Conduct pull-down assays under stress and non-stress conditions

  • Identify stress-specific binding partners using mass spectrometry

  • Verify interactions using bacterial two-hybrid or FRET analyses

• Membrane integrity assessment:

  • Measure membrane permeability using fluorescent dyes (SYTOX Green)

  • Assess membrane potential with voltage-sensitive probes

  • Analyze membrane lipid composition changes in response to stress

• In vivo relevance:

  • Evaluate ΔyeaL mutant virulence in animal models under stress conditions

  • Measure bacterial loads in tissues following infection

  • Compare competitive indices between wild-type and mutant strains

This approach is informed by studies of acid stress response in Salmonella, which have identified membrane proteins like FliC that contribute to acid-induced phenotypes. Given that Salmonella encounters acidic environments in the stomach and within macrophage phagosomes, investigating YeaL's role in acid stress response is particularly relevant .

How can researchers assess the immunogenicity of recombinant YeaL protein?

Assessing the immunogenicity of recombinant YeaL protein requires a multi-dimensional approach that examines both humoral and cellular immune responses. Based on methodologies used for other Salmonella membrane proteins, the following comprehensive protocol is recommended:

• Humoral immunity assessment:

  • ELISA-based antibody detection:

    • Coat plates with purified rYeaL protein

    • Test sera from infected animals or patients

    • Determine antibody titers for different isotypes (IgG, IgM, IgA)

    • Perform competitive ELISA to assess epitope specificity

  • Western blot analysis:

    • Run rYeaL on SDS-PAGE and transfer to membranes

    • Probe with sera from infected subjects

    • Compare reactivity patterns between different infection stages

  • Epitope mapping:

    • Generate overlapping peptides spanning the YeaL sequence

    • Identify immunodominant regions using antibody binding assays

• Cellular immunity assessment:

  • T cell proliferation assays:

    • Isolate peripheral blood mononuclear cells (PBMCs) or spleen cells

    • Stimulate with rYeaL and measure proliferation using [³H]-thymidine incorporation or CFSE dilution

    • Determine stimulation indices compared to unstimulated controls

  • Flow cytometry for antigen-specific T cells:

    • Use intracellular cytokine staining to detect IFN-γ production

    • Assess CD4+ and CD8+ T cell activation (CD69 expression)

    • Quantify the frequency of YeaL-specific T cells

  • ELISPOT assays:

    • Enumerate cytokine-producing cells at the single-cell level

    • Detect IFN-γ, IL-2, IL-4, or IL-17 to characterize the response type

• Cytokine profiling:

  • Measure cytokine production in culture supernatants using ELISA or multiplex assays

  • Compare cytokine patterns induced by YeaL with those induced by other Salmonella antigens

  • Assess the balance between pro-inflammatory and regulatory cytokines

This methodological approach is based on successful techniques used to characterize the immunogenicity of Salmonella OmpA, which was found to stimulate CD8+ T cells to produce IFN-γ and induce proinflammatory cytokines in synovial fluid mononuclear cells from patients with reactive arthritis .

What is the potential of YeaL as a diagnostic marker for Salmonella infections?

Evaluating YeaL's potential as a diagnostic marker for Salmonella infections requires a systematic assessment of its specificity, sensitivity, and practical applicability in clinical settings. The following methodological approach would be appropriate:

• Specificity assessment:

  • Sequence homology analysis:

    • Compare YeaL sequences across Salmonella serovars to identify conserved regions

    • Conduct BLAST searches against other bacterial genera to identify potential cross-reactivity

    • Select unique peptide regions specific to Salmonella for antibody development

  • Cross-reactivity testing:

    • Test rYeaL-based assays against a panel of non-Salmonella enteric pathogens

    • Include closely related Enterobacteriaceae (E. coli, Shigella, Klebsiella)

    • Evaluate false positive rates in diverse clinical samples

• Sensitivity evaluation:

  • Expression profiling during infection:

    • Determine if YeaL is expressed at detectable levels during different stages of infection

    • Assess expression in various growth conditions mimicking host environments

    • Quantify protein abundance relative to other potential diagnostic targets

  • Detection limit studies:

    • Determine the minimum concentration of YeaL detectable by antibody-based methods

    • Compare with bacterial load thresholds in clinical infections

    • Evaluate detection in complex biological matrices (blood, stool, urine)

• Diagnostic assay development:

  • ELISA-based detection systems:

    • Develop sandwich ELISA using anti-YeaL antibodies for antigen capture

    • Optimize signal amplification methods for improved sensitivity

    • Determine appropriate cutoff values using ROC curve analysis

  • Point-of-care test formats:

    • Adapt YeaL detection to lateral flow immunoassay formats

    • Evaluate stability and performance under field conditions

    • Assess time-to-result and user-friendliness

• Clinical validation:

  • Retrospective studies:

    • Test archived samples from confirmed Salmonella cases and controls

    • Calculate sensitivity, specificity, positive and negative predictive values

    • Compare performance against current gold standard methods

  • Prospective clinical trials:

    • Implement YeaL-based assays alongside standard diagnostic methods

    • Evaluate performance across diverse patient populations and infection severities

    • Assess utility in detecting specific Salmonella serovars

Drawing parallels from studies of other Salmonella proteins, such as the FliC protein that showed reactivity with sera from typhoid patients (Widal positive) but not with sera from patients with non-typhoidal fever, YeaL should be evaluated for its ability to distinguish between Salmonella and non-Salmonella infections as well as between different Salmonella serovars .

How does the immune response to YeaL compare with responses to other Salmonella membrane proteins?

Comparing the immune response to YeaL with responses to other Salmonella membrane proteins requires a systematic investigation across multiple immune parameters. Based on the available research on Salmonella membrane proteins, particularly OmpA and FliC, the following comparative analysis approach is recommended:

• Comparative T cell response analysis:

  • T cell subset activation patterns:

    • Compare CD4+ versus CD8+ T cell responses to YeaL, OmpA, and other membrane proteins

    • Research indicates that OmpA preferentially activates CD8+ T cells in synovial fluid of reactive arthritis patients

    • Determine if YeaL follows a similar pattern or activates different T cell populations

  • Cytokine profile comparison:

    • Measure IFN-γ, TNF-α, IL-2, IL-4, IL-17 production in response to different proteins

    • OmpA stimulates IFN-γ production, suggesting a Th1-biased response

    • Assess whether YeaL induces similar or distinct cytokine patterns

• Antibody response characteristics:

  • Isotype distribution:

    • Compare IgG, IgM, and IgA responses to different membrane proteins

    • Analyze IgG subclass patterns (IgG1, IgG2, IgG3, IgG4)

    • Determine if YeaL elicits a distinct antibody isotype profile

  • Epitope recognition patterns:

    • Map immunodominant epitopes across different membrane proteins

    • Compare linear versus conformational epitope recognition

    • Assess epitope conservation across Salmonella serovars

• Host cell interaction differences:

  • Antigen presentation pathways:

    • Determine MHC class I versus class II presentation of different proteins

    • OmpA shows evidence of CD8+ T cell activation, suggesting MHC-I presentation

    • Investigate if YeaL follows similar or different presentation pathways

  • Innate immune activation:

    • Compare PRR (Pattern Recognition Receptor) engagement by different proteins

    • Measure activation of dendritic cells, macrophages, and neutrophils

    • Assess inflammasome activation potential

• Methodological comparison table:

This comparative approach would provide insights into whether YeaL plays a unique immunological role or shares functional redundancy with other Salmonella membrane proteins. Understanding these differences could inform the development of diagnostic tests or vaccine candidates targeting specific immune responses .

What are the potential applications of YeaL protein in vaccine development?

Evaluating YeaL's potential as a vaccine candidate requires a comprehensive assessment of its immunogenicity, conservation, and protective capacity. Based on approaches used for other Salmonella membrane proteins, the following research methodology is recommended:

• Antigen conservation and expression analysis:

  • Sequence conservation assessment:

    • Analyze YeaL sequence conservation across multiple Salmonella serovars

    • Identify conserved epitopes that could provide broad protection

    • Assess natural variation in circulating strains

  • Expression analysis during infection:

    • Determine if YeaL is expressed in vivo during infection

    • Quantify expression levels in different host microenvironments

    • Confirm accessibility to the immune system in intact bacteria

• Immunogenicity studies:

  • Animal immunization protocols:

    • Immunize mice with purified rYeaL using different adjuvants

    • Test multiple immunization routes (subcutaneous, intranasal, oral)

    • Assess dose-dependent immune responses

    • Measure antibody titers and T cell responses

  • Immune response characterization:

    • Determine the balance between humoral and cellular immunity

    • Characterize cytokine profiles to assess Th1/Th2/Th17 polarization

    • Evaluate mucosal immune responses critical for enteric pathogens

• Protective efficacy assessment:

  • Challenge studies:

    • Challenge immunized animals with virulent Salmonella

    • Measure bacterial loads in tissues and survival rates

    • Compare protection against homologous and heterologous strains

  • Passive immunization:

    • Transfer serum from immunized to naïve animals

    • Assess protection to determine antibody contribution

    • Perform T cell adoptive transfer to evaluate cellular protection

• Adjuvant and delivery optimization:

  • Adjuvant comparison:

    • Test aluminum salts, oil-in-water emulsions, and TLR agonists

    • Assess impact on immunogenicity and protection

    • Evaluate safety profiles of different formulations

  • Advanced delivery platforms:

    • Evaluate YeaL incorporation into nanoparticles or liposomes

    • Test DNA vaccines encoding YeaL

    • Assess vectored vaccines using viral or bacterial vectors

• Combination vaccine strategies:

  • Multi-antigen formulations:

    • Combine YeaL with other immunogenic Salmonella proteins (OmpA, FliC)

    • Assess additive or synergistic protection

    • Evaluate epitope competition or interference

Drawing from research on Salmonella OmpA, which has shown significant immunogenicity and T cell responses in patients with reactive arthritis, YeaL could be evaluated for similar properties. OmpA's ability to stimulate CD8+ T cells and induce IFN-γ production suggests potential for cellular immunity, which is critical for protection against intracellular pathogens like Salmonella .

How can structural biology techniques be applied to elucidate YeaL's function?

Elucidating the structure-function relationship of YeaL requires an integrated structural biology approach that accommodates the challenges associated with membrane protein analysis. The following methodological framework is recommended:

• X-ray crystallography approach:

  • Protein production optimization:

    • Screen detergents for optimal solubilization (DDM, LDAO, OG)

    • Test truncated constructs to remove flexible regions

    • Explore fusion partners (T4 lysozyme, BRIL) to aid crystallization

  • Crystallization screening:

    • Utilize sparse matrix and lipidic cubic phase (LCP) methods

    • Optimize temperature, pH, and precipitant conditions

    • Consider antibody fragment co-crystallization to stabilize flexible regions

  • Data collection and structure determination:

    • Use synchrotron radiation for high-resolution diffraction data

    • Apply molecular replacement or experimental phasing methods

    • Refine structure with membrane protein-specific parameters

• Cryo-electron microscopy (cryo-EM):

  • Sample preparation strategies:

    • Reconstitute YeaL into nanodiscs or amphipols

    • Optimize protein concentration and buffer conditions

    • Screen grid types and vitrification parameters

  • Data acquisition and processing:

    • Collect images on high-end cryo-EM systems with energy filters

    • Apply 2D and 3D classification to separate conformational states

    • Perform 3D refinement to obtain high-resolution reconstructions

• NMR spectroscopy applications:

  • Sample preparation:

    • Express isotopically labeled protein (¹⁵N, ¹³C, ²H)

    • Optimize detergent micelles or nanodiscs for solution NMR

    • Prepare oriented samples for solid-state NMR

  • Experimental approaches:

    • Conduct HSQC experiments to assess protein folding

    • Perform backbone and side-chain assignments

    • Apply relaxation measurements to identify dynamic regions

    • Use paramagnetic probes to determine topology

• Integrative structural biology:

  • Computational modeling:

    • Apply homology modeling based on related membrane proteins

    • Perform molecular dynamics simulations in lipid bilayers

    • Use evolutionary coupling analysis to predict contacts

  • Complementary techniques:

    • Hydrogen-deuterium exchange mass spectrometry (HDX-MS)

    • Cross-linking mass spectrometry (XL-MS)

    • Small-angle X-ray scattering (SAXS) with detergent-solubilized protein

    • Electron paramagnetic resonance (EPR) spectroscopy

• Structure-function validation:

  • Site-directed mutagenesis:

    • Target predicted functional residues based on structural data

    • Assess impact on protein stability and function

    • Perform activity assays with mutants to validate mechanistic hypotheses

  • Ligand binding studies:

    • Use surface plasmon resonance or isothermal titration calorimetry

    • Perform computational docking to identify potential binding sites

    • Validate interactions with co-crystallization or NMR titration experiments

This comprehensive approach draws on methodologies that have successfully elucidated structures of other bacterial membrane proteins. Understanding YeaL's structure would provide crucial insights into its membrane topology, potential binding partners, and mechanistic role in Salmonella pathogenesis .

What cutting-edge genome editing techniques can be applied to study YeaL function in Salmonella?

To comprehensively investigate YeaL function in Salmonella, researchers can leverage several cutting-edge genome editing techniques that offer precision, efficiency, and versatility. The following methodological framework provides a systematic approach:

• CRISPR-Cas9 based approaches:

  • Complete gene knockout:

    • Design sgRNAs targeting the yeaL coding sequence

    • Introduce frameshift mutations or complete gene deletions

    • Include scarless editing to minimize polar effects on adjacent genes

  • Point mutation generation:

    • Create specific amino acid substitutions to test structure-function hypotheses

    • Target conserved residues identified through sequence analysis

    • Generate variants mimicking naturally occurring polymorphisms

  • CRISPRi for conditional repression:

    • Use catalytically dead Cas9 (dCas9) fused to repressors

    • Enable tunable and reversible gene repression

    • Apply inducible systems for temporal control of expression

• Recombineering techniques:

  • Lambda Red recombination:

    • Generate precise deletions, insertions, or point mutations

    • Incorporate unmarked mutations using counterselection methods

    • Design allelic exchange constructs with flanking homology regions

  • FRUIT (Flexible Recombineering Using Integration of thyA):

    • Leverage thyA-based selection/counterselection for seamless modifications

    • Generate multiple sequential mutations in the same strain

    • Create precise chromosomal fusions for localization studies

• Advanced reporter systems:

  • Transcriptional reporters:

    • Create yeaL promoter fusions with fluorescent proteins

    • Use dual-reporter systems to normalize expression data

    • Apply destabilized reporters for temporal expression dynamics

  • Translational fusions:

    • Generate C-terminal protein fusions preserving membrane localization

    • Incorporate split fluorescent proteins for protein interaction studies

    • Develop FRET-based sensors to monitor conformational changes

• Genome-wide interaction mapping:

  • Transposon insertion sequencing (TIS):

    • Perform TIS in yeaL mutant backgrounds to identify synthetic phenotypes

    • Compare genetic interaction networks across infection-relevant conditions

    • Identify compensatory pathways activated in yeaL mutants

  • CRISPR interference screens:

    • Conduct genome-wide CRISPRi screens in yeaL mutant backgrounds

    • Identify condition-specific genetic interactions

    • Map the functional network surrounding YeaL

• In vivo studies with engineered strains:

  • Infection model applications:

    • Challenge models with yeaL variants to assess virulence

    • Use dual-strain competition assays to measure fitness effects

    • Implement tissue-specific or temporal gene control during infection

  • Host-pathogen interaction mapping:

    • Apply proximity labeling techniques (BioID, APEX) in vivo

    • Identify host proteins interacting with YeaL during infection

    • Create reporter strains for visualizing YeaL expression in host tissues

This methodological framework draws upon approaches used to study other Salmonella membrane proteins like IgaA, which was shown to modulate the RcsC-YojN-RcsB phosphorelay system affecting virulence. Similar approaches could reveal whether YeaL participates in stress response pathways, virulence regulation, or host-pathogen interactions .