Recombinant Shigella sonnei Bifunctional protein aas (aas)

What is the basic structure and function of Shigella sonnei Bifunctional protein aas(aas)?

Shigella sonnei Bifunctional protein aas(aas) is a 719-amino acid protein that plays a role in bacterial metabolism. The protein has multiple functional domains which contribute to its bifunctional nature. When working with the recombinant version, researchers typically use an N-terminal His-tagged form expressed in E. coli .

For structural studies, begin with:

• Secondary structure prediction using algorithms such as PSIPRED

• Domain organization analysis using InterPro or SMART

• Homology modeling if crystal structure is unavailable

• Circular dichroism spectroscopy to experimentally confirm secondary structure elements

Function can be assessed through enzyme activity assays relevant to the bifunctional nature of the protein, complementation studies in knockout strains, and protein-protein interaction analyses.

What are the optimal storage conditions for recombinant Shigella sonnei Bifunctional protein aas(aas)?

The recombinant protein should be stored at -20°C/-80°C upon receipt, with aliquoting necessary for multiple use. Avoid repeated freeze-thaw cycles as they can compromise protein integrity. For working aliquots, storage at 4°C for up to one week is acceptable .

Methodology for proper storage:

• Upon reconstitution in deionized sterile water (concentration of 0.1-1.0 mg/mL), add glycerol to a final concentration of 50%

• Prepare small single-use aliquots in screw-cap microcentrifuge tubes

• Flash freeze aliquots in liquid nitrogen before transferring to -80°C

• Maintain a temperature log of the storage unit

• For short-term use, store working aliquots at 4°C for no more than one week

How should recombinant Shigella sonnei Bifunctional protein aas(aas) be reconstituted for experimental use?

Proper reconstitution ensures optimal protein activity. The lyophilized protein should be briefly centrifuged prior to opening to bring contents to the bottom. Reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL. For long-term storage, add glycerol to a final concentration of 5-50% .

Reconstitution protocol:

• Equilibrate the lyophilized protein to room temperature

• Centrifuge the vial at 10,000 × g for 1 minute

• Add appropriate volume of sterile deionized water

• Gently mix by inversion or mild vortexing until completely dissolved

• Aliquot immediately after reconstitution

• Verify protein concentration using Bradford or BCA assays

• Assess protein activity using functional assays

What expression systems are suitable for producing recombinant Shigella sonnei Bifunctional protein aas(aas)?

Comparison of expression systems:

Select the expression system based on your specific requirements for protein yield, purity, and functional characteristics.

What are the best methods for assessing the purity and integrity of recombinant Shigella sonnei Bifunctional protein aas(aas)?

Purity and integrity assessment is crucial for reliable experimental outcomes. The recombinant protein should achieve greater than 90% purity as determined by SDS-PAGE .

Comprehensive purity analysis methodology:

• SDS-PAGE analysis: Run protein samples on 10-12% gels with appropriate molecular weight markers

• Western blot analysis: Use anti-His antibodies to confirm identity of the recombinant protein

• Size exclusion chromatography: Analyze oligomeric state and detect aggregates

• Mass spectrometry: Confirm molecular weight and sequence coverage

• Dynamic light scattering: Assess homogeneity and detect aggregates

• Analytical ultracentrifugation: Determine sedimentation coefficient and molecular weight in solution

For assessing functional integrity, develop enzyme activity assays specific to the bifunctional nature of the protein.

How can I optimize the yield of soluble recombinant Shigella sonnei Bifunctional protein aas(aas) during expression?

Obtaining high yields of soluble recombinant protein is often challenging. Similar to other Shigella proteins that have traditionally been produced in cell-based heterologous expression systems, aas protein production may face limitations regarding recovery and solubility .

Optimization strategies:

• Expression temperature modulation (16-30°C)

• IPTG concentration titration (0.1-1.0 mM)

• Use of specialized E. coli strains (BL21, Rosetta, Origami)

• Co-expression with chaperones (GroEL/GroES, DnaK/DnaJ)

• Fusion tags beyond His-tag (MBP, GST, SUMO)

• Alternative approaches:

  • Cell-free protein synthesis (CFPS), which has shown success with other Shigella proteins

  • Codon optimization for expression host

  • Autoinduction media instead of IPTG induction

Monitor expression using small-scale test expressions before scaling up to production levels.

What functional assays are appropriate for characterizing recombinant Shigella sonnei Bifunctional protein aas(aas)?

Functional characterization requires assays specific to the bifunctional nature of the protein. While the specific functions of aas in Shigella sonnei aren't detailed in the search results, functional analysis should include:

• Enzyme kinetics assays for both functional domains

• Substrate specificity determination

• pH and temperature optimum characterization

• Cofactor requirements assessment

• Inhibitor screening

• Protein-protein interaction studies using:

  • Pull-down assays with potential binding partners

  • Surface plasmon resonance for binding kinetics

  • Isothermal titration calorimetry for thermodynamic parameters

• Structural changes upon substrate binding using circular dichroism or fluorescence spectroscopy

Develop positive and negative controls for each assay to ensure validity of results.

How can recombinant Shigella sonnei Bifunctional protein aas(aas) be integrated into vaccine development approaches?

While the specific role of aas protein in vaccine development isn't directly mentioned in the search results, Shigella sonnei proteins have been extensively studied for vaccine applications. Recent advances in Shigella vaccine development include multiplex binding assays and chimeric protein approaches .

Methodological considerations for aas protein in vaccine development:

• Epitope mapping to identify immunogenic regions:

  • Use computational prediction tools

  • Experimental validation with peptide arrays

  • B-cell and T-cell epitope identification

• Chimeric protein design strategies:

  • Selection of immunogenic regions (similar to the approach used with IpaD, StxB, and TolC proteins)

  • In silico analysis of physicochemical characteristics and protein structures

  • Assessment of B and T cell epitopes

  • Molecular docking studies

• Adjuvant selection and formulation optimization

• Animal model testing:

  • Immunogenicity assessment

  • Protection studies

  • Dosing optimization

• Assessment of cross-protection against multiple Shigella serotypes

What are the challenges in structural studies of recombinant Shigella sonnei Bifunctional protein aas(aas)?

Structural studies of recombinant proteins face several challenges, particularly for multifunctional bacterial proteins like aas.

Methodological approach to overcome structural study challenges:

• Limited solubility and aggregation:

  • Screen multiple buffer conditions using differential scanning fluorimetry

  • Employ detergents for stabilization if membrane-associated

  • Test truncated constructs focusing on individual domains

• Crystallization difficulties:

  • High-throughput crystallization screening (1000+ conditions)

  • Surface entropy reduction mutations

  • Crystallization chaperones or antibody fragments

  • LCP (Lipidic Cubic Phase) crystallization if membrane-associated

• Alternative structural methods:

  • Cryo-electron microscopy for larger assemblies

  • Small-angle X-ray scattering (SAXS) for solution structure

  • NMR spectroscopy for dynamic regions

  • Hydrogen-deuterium exchange mass spectrometry for conformational changes

• Computational approaches:

  • AlphaFold2 or RoseTTAFold prediction

  • Molecular dynamics simulations

  • Integrative structural modeling combining experimental and computational data

How does recombinant Shigella sonnei Bifunctional protein aas(aas) interact with the host immune system?

Understanding host-pathogen interactions is crucial for vaccine development and therapeutic interventions. While specific information about aas protein's interaction with the immune system isn't provided in the search results, the methodology for studying such interactions follows established approaches.

Comprehensive experimental workflow:

• In silico analysis:

  • Prediction of potential immunogenic epitopes

  • Homology to known immunomodulatory proteins

  • Structural analysis for potential PAMPs (Pathogen-Associated Molecular Patterns)

• In vitro immune cell studies:

  • Dendritic cell activation and maturation assays

  • Cytokine production profiling using ELISA or multiplex assays

  • T-cell proliferation and differentiation analysis

  • Phagocytosis assays with macrophages

  • NET formation with neutrophils

• Signaling pathway analysis:

  • NF-κB activation assays

  • MAPK pathway analysis

  • Pattern recognition receptor engagement studies

• In vivo models:

  • Transgenic mouse models

  • Infection studies with recombinant Shigella strains expressing modified aas protein

  • Adoptive transfer experiments to assess specific immune cell contributions

• Human studies:

  • Analysis of immune responses in infected individuals

  • HLA binding and T-cell epitope validation

How can site-directed mutagenesis be applied to study the functional domains of Shigella sonnei Bifunctional protein aas(aas)?

Site-directed mutagenesis is a powerful approach to dissect protein function. For a bifunctional protein like aas, this technique can help understand the contribution of each domain and identify critical residues.

Systematic mutagenesis protocol:

• Structure-guided target selection:

  • Conserved residues identified through sequence alignment

  • Catalytic site residues predicted through structural analysis

  • Interface residues between domains

  • Surface-exposed residues potentially involved in protein-protein interactions

• Mutagenesis strategy design:

  • Alanine scanning of selected regions

  • Conservative vs. non-conservative substitutions

  • Domain swapping with homologous proteins

  • Creation of truncated constructs

• Functional analysis of mutants:

  • Expression and solubility assessment

  • Activity assays for each functional domain

  • Structural integrity verification (CD spectroscopy, thermal stability)

  • In vivo complementation studies

• Data integration:

  • Correlation of structural features with functional outcomes

  • Computational modeling of mutant effects

  • Evolutionary analysis of mutated positions

What are the best approaches for detecting protein-protein interactions involving Shigella sonnei Bifunctional protein aas(aas)?

Understanding protein-protein interactions is essential for elucidating cellular functions. For studying aas protein interactions, employ both in vitro and in vivo methodologies.

Comprehensive interaction analysis workflow:

• In silico prediction of potential interaction partners:

  • Sequence-based prediction tools

  • Structural docking simulations

  • Co-evolution analysis

• In vitro interaction studies:

  • Pull-down assays using His-tagged aas protein

  • Surface plasmon resonance for binding kinetics

  • Isothermal titration calorimetry for thermodynamic parameters

  • Analytical ultracentrifugation for complex formation

  • Cross-linking coupled with mass spectrometry

• In vivo interaction validation:

  • Bacterial two-hybrid systems

  • Co-immunoprecipitation from Shigella lysates

  • Proximity labeling approaches (BioID, APEX)

  • Fluorescence resonance energy transfer (FRET)

• Functional validation of interactions:

  • Co-expression and co-purification studies

  • Activity assays in presence and absence of partners

  • Mutational analysis of interaction interfaces

How should researchers troubleshoot expression and purification issues with recombinant Shigella sonnei Bifunctional protein aas(aas)?

Troubleshooting expression and purification problems requires systematic analysis of each step in the workflow.

Systematic troubleshooting methodology:

• Expression issues:

  • Verify plasmid sequence integrity

  • Test multiple E. coli strains (BL21, Rosetta, Arctic Express)

  • Optimize induction conditions (temperature, IPTG concentration, duration)

  • Examine protein solubility in different lysis buffers

  • Consider codon optimization for E. coli expression

• Purification challenges:

  • Optimize lysis conditions (detergents, sonication parameters)

  • Adjust imidazole concentration in binding and elution buffers

  • Test different pH conditions for His-tag binding

  • Consider on-column refolding if protein is in inclusion bodies

  • Add stabilizing agents (glycerol, reducing agents, specific ions)

• Protein quality issues:

  • Analyze by dynamic light scattering for aggregation

  • Perform thermal shift assays to identify stabilizing buffer conditions

  • Check for proteolytic degradation with protease inhibitors

  • Verify protein identity by mass spectrometry

  • Assess activity immediately after purification vs. after storage

• Alternative strategies:

  • Consider cell-free protein synthesis systems

  • Explore fusion partners beyond His-tag (MBP, GST, SUMO)

  • Test expression of individual domains separately

What are the considerations for designing antibodies against Shigella sonnei Bifunctional protein aas(aas)?

Antibody development requires careful antigen design and validation strategies. For aas protein, consider both polyclonal and monoclonal approaches.

Antibody development workflow:

• Antigen preparation strategies:

  • Full-length recombinant protein

  • Selected domains expressed separately

  • Synthetic peptides from predicted antigenic regions

  • Multiple antigen peptide (MAP) systems for enhanced immunogenicity

• Immunization protocols:

  • Animal selection (rabbits for polyclonal, mice for monoclonal)

  • Adjuvant selection and optimization

  • Immunization schedule (primary and boosters)

  • Serum collection and titer monitoring

• Antibody purification methods:

  • Protein A/G affinity chromatography

  • Antigen-specific affinity purification

  • Ion exchange chromatography for IgG subclass separation

• Validation studies:

  • Western blot against recombinant protein and native Shigella lysates

  • Immunoprecipitation efficiency

  • Immunofluorescence for localization studies

  • Epitope mapping to confirm specificity

  • Cross-reactivity testing with related bacterial proteins

• Application optimization:

  • Antibody concentration determination for each application

  • Buffer optimization for storage stability

  • Conjugation strategies for detection applications

How can researchers effectively analyze post-translational modifications of recombinant Shigella sonnei Bifunctional protein aas(aas)?

Post-translational modifications (PTMs) can significantly impact protein function. Analysis of PTMs requires specialized techniques and careful sample preparation.

Comprehensive PTM analysis protocol:

• Predictive analysis:

  • In silico prediction of potential modification sites

  • Evolutionary conservation of modification sites

  • Structural context of predicted sites

• Mass spectrometry-based approaches:

  • Sample preparation optimization (enrichment strategies)

  • Proteolytic digestion optimization

  • LC-MS/MS analysis with multiple fragmentation methods

  • Data analysis with PTM-specific search algorithms

• Site-specific validation:

  • Site-directed mutagenesis of modified residues

  • Antibodies specific for the modification

  • Functional assays comparing wild-type and mutant proteins

• PTM-specific analytical techniques:

  • Phosphorylation: Phos-tag gels, phospho-specific antibodies

  • Glycosylation: Lectin blotting, glycosidase treatments

  • Acetylation: Acetyl-lysine antibodies

  • Ubiquitination: Ubiquitin pull-down assays

• Comparative analysis:

  • Native protein from Shigella vs. recombinant protein

  • Modification patterns under different growth conditions

  • Temporal dynamics of modifications

How does Shigella sonnei Bifunctional protein aas(aas) compare structurally and functionally to homologous proteins in other bacterial species?

Comparative analysis provides insights into evolutionary conservation and functional importance. For aas protein, systematic comparison with homologs is essential.

Comparative analysis methodology:

• Homolog identification:

  • BLAST searches against bacterial genomes

  • Profile-based methods (HMMer, PSI-BLAST)

  • Structural homology detection (DALI, FATCAT)

• Sequence-based comparison:

  • Multiple sequence alignment with MUSCLE or MAFFT

  • Conservation analysis with ConSurf or Rate4Site

  • Functional domain prediction and comparison

  • Identification of species-specific insertions/deletions

• Structural comparison:

  • Homology modeling of uncharacterized homologs

  • Superposition and RMSD calculation

  • Active site geometry comparison

  • Surface electrostatics analysis

• Functional comparison:

  • Enzymatic activity assays across species

  • Substrate specificity profiling

  • Complementation studies in knockout strains

  • Temperature and pH optima determination

• Evolutionary analysis:

  • Phylogenetic tree construction

  • Selection pressure analysis (dN/dS ratio)

  • Ancestral sequence reconstruction

  • Correlation of functional differences with evolutionary distance

What is the role of Shigella sonnei Bifunctional protein aas(aas) in the context of virulence and pathogenicity mechanisms?

Understanding the role of specific proteins in pathogenicity provides valuable insights for therapeutic development. While specific information about aas protein's role in virulence isn't provided in the search results, Shigella sonnei employs several virulence mechanisms .

Investigation methodology:

• Mutant construction and analysis:

  • Gene deletion using λ Red recombineering

  • Complementation studies

  • Conditional expression systems

• Virulence phenotype assessment:

  • Invasion assays in cell culture models

  • Intracellular replication quantification

  • Cell-to-cell spread assays

  • Animal infection models

• Interaction with host factors:

  • Pull-down experiments with host cell lysates

  • Yeast two-hybrid screening

  • Proximity labeling in infected cells

  • Co-localization studies during infection

• Expression analysis during infection:

  • qRT-PCR for transcriptional changes

  • Western blot for protein expression levels

  • Reporter fusions for temporal expression patterns

  • Single-cell analysis in infection models

• Comparative analysis across Shigella species:

  • Presence and conservation in S. flexneri and other species

  • Function in different genetic backgrounds

  • Contribution to species-specific virulence traits

How does the genetic context of the aas gene in Shigella sonnei influence its expression and regulation?

Gene expression and regulation are influenced by genomic context and regulatory networks. Understanding these aspects for the aas gene requires integrated analysis approaches.

Investigation protocol:

• Genomic context analysis:

  • Operon structure determination

  • Identification of adjacent genes and potential functional relationships

  • Comparative genomics across Shigella strains and related species

  • Mobile genetic element identification in proximity

• Promoter and regulatory element characterization:

  • Promoter mapping using 5' RACE

  • Transcription start site determination

  • Identification of transcription factor binding sites

  • Reporter gene assays to assess promoter strength

• Expression analysis under various conditions:

  • qRT-PCR under different growth phases

  • Response to environmental stresses (pH, temperature, oxygen)

  • Changes during infection models

  • Single-cell expression heterogeneity

• Regulatory network mapping:

  • Transcriptomics following deletion/overexpression

  • ChIP-seq to identify direct regulators

  • Protein-DNA interaction studies

  • Integration with known Shigella regulatory networks

• Post-transcriptional regulation:

  • mRNA stability assessment

  • Identification of small RNAs affecting expression

  • Ribosome profiling for translation efficiency

  • RNA structure probing for regulatory elements