Recombinant Salmonella choleraesuis Bifunctional protein aas (aas)

What is the basic structure of Salmonella choleraesuis Bifunctional protein aas (aas)?

The Salmonella choleraesuis Bifunctional protein aas (aas) is a full-length protein consisting of 719 amino acids (1-719aa), identified by the UniProt accession number Q57KA7. The protein contains multiple functional domains that enable its bifunctional nature. The amino acid sequence includes distinct regions responsible for different enzymatic activities within a single protein structure .

The primary sequence analysis reveals characteristic features of bifunctional enzymes, including conserved active site regions and binding domains. Similar to other bifunctional enzymes studied in bacterial systems, the aas protein likely contains separate structural domains with distinct catalytic functions while maintaining a unified tertiary structure that coordinates these activities .

How does the bifunctionality of aas protein manifest at the molecular level?

The bifunctionality of the aas protein manifests through distinct catalytic domains within the same polypeptide chain. Based on analysis of similar bifunctional proteins, the aas protein contains separate active sites for each of its functions, though these sites may communicate allosterically .

From the amino acid sequence (MLFGFFRNLFRVLYR...), we can identify regions rich in hydrophobic residues that likely form critical binding interfaces, as well as more polar regions that may constitute catalytic centers . The sequence contains multiple potential binding motifs (e.g., TSGSEGHPKG) that may interact with different substrates, enabling the protein to perform separate but related enzymatic functions. The structure likely allows for conformational changes that regulate the switch between different catalytic functions.

What expression systems are most effective for producing recombinant Salmonella choleraesuis Bifunctional protein aas?

The most effective expression system documented for Salmonella choleraesuis Bifunctional protein aas is Escherichia coli. The recombinant protein is typically expressed with an N-terminal His-tag to facilitate purification . This expression system provides several advantages:

• High yield production of soluble protein

• Compatibility with the bacterial origin of the protein

• Established purification protocols using His-tag affinity chromatography

• Scalability for research applications

For optimal expression, consider the following methodological parameters:

This approach draws upon established protocols for similar bifunctional bacterial proteins and minimizes the formation of inclusion bodies while maintaining functional integrity .

What purification methods provide the highest yield and purity for recombinant aas protein?

For purifying recombinant Salmonella choleraesuis Bifunctional protein aas with His-tag, a multi-step purification protocol yields optimal results:

• Initial Immobilized Metal Affinity Chromatography (IMAC): Using Ni-NTA or Co-NTA resins with a gradient elution (50-250 mM imidazole in Tris/PBS-based buffer, pH 8.0) to capture the His-tagged protein .

• Size Exclusion Chromatography (SEC): To remove aggregates and ensure monodispersity of the protein sample.

• Ion Exchange Chromatography (optional): For removing contaminants with different charge properties.

The purification process should yield protein with greater than 90% purity as determined by SDS-PAGE . For long-term storage, the purified protein should be formulated in Tris/PBS-based buffer with 6% trehalose at pH 8.0, and stored with 5-50% glycerol (recommended final concentration 50%) at -20°C/-80°C to prevent activity loss through freeze-thaw cycles .

How can researchers validate the dual functionality of recombinant aas protein in vitro?

Validating the dual functionality of recombinant aas protein requires separate assays for each catalytic function. Based on structural homology with other bifunctional enzymes, a comprehensive validation approach should include:

Similar validation approaches have been successful for other bifunctional enzymes like the alanine racemase from Taibaiella chishuiensis, which required comprehensive analysis of both activities to confirm its bifunctional nature .

What are the critical parameters for maintaining stability and activity of the recombinant aas protein?

Maintaining the stability and activity of recombinant Salmonella choleraesuis Bifunctional protein aas requires careful attention to several parameters:

For experimental applications, we recommend reconstituting the lyophilized protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL . The addition of 50% glycerol and storage in small aliquots can prevent repeated freeze-thaw cycles that would compromise protein activity.

How does the aas protein from Salmonella choleraesuis compare structurally and functionally to homologous proteins in other bacterial species?

Comparative analysis of the aas protein with homologous bifunctional proteins reveals important evolutionary and functional relationships. While specific comparison data for the aas protein is limited in the search results, we can draw parallels from studies of other bifunctional enzymes:

• Sequence Conservation: Multiple sequence alignment of aas with homologous proteins from related bacterial species would likely reveal highly conserved active site residues indicated by asterisks (*), conservation between groups with highly similar characteristics indicated by colons (:), and conservation between groups with less similar characteristics indicated by periods (.) .

• Structural Domains: Similar to the bifunctional alanine racemase from Taibaiella chishuiensis, the aas protein likely contains distinct structural domains that evolved to carry out separate functions while maintaining structural integrity .

• Functional Adaptation: The bifunctionality may represent an evolutionary adaptation that allows for coordinated regulation of related metabolic processes, as seen in other bifunctional bacterial enzymes .

• Species-Specific Variations: Variations in non-catalytic regions likely reflect adaptation to different bacterial lifestyles and environmental niches.

A thorough comparative study would employ phylogenetic analysis, homology modeling, and functional assays to map the evolutionary trajectory of these bifunctional proteins across bacterial species and identify species-specific functional adaptations.

What are the potential roles of aas protein in Salmonella choleraesuis pathogenicity and host-pathogen interactions?

The role of aas protein in Salmonella choleraesuis pathogenicity may be significant, though direct evidence from the search results is limited. Drawing parallels with other Salmonella proteins:

• Metabolic Adaptation: As a bifunctional protein, aas may help the pathogen adapt to different host environments by efficiently coordinating related metabolic functions, similar to how other Salmonella proteins mediate survival in host cells .

• Immune Modulation: Like the Salmonella effector protein SopD that modulates inflammatory responses by targeting Rab8 , aas might influence host signaling pathways through its enzymatic activities.

• Virulence Regulation: The bifunctional nature could allow for coordinated regulation of virulence factors depending on environmental cues within the host.

• Survival under Stress: The protein may contribute to bacterial survival under host-imposed stress conditions by maintaining essential metabolic functions.

To investigate these potential roles, researchers should consider experimental approaches such as:

• Creating knock-out mutants to assess virulence attenuation

• Immunoprecipitation studies to identify host interaction partners

• Infection studies in cell culture and animal models

• Transcriptomic analysis to identify conditions that regulate aas expression

Understanding the role of aas in pathogenicity could provide insights for vaccine development approaches, similar to how recombinant attenuated Salmonella strains have been used to express heterologous antigens for vaccine purposes .

How might researchers design inhibitors specific to the bifunctional activities of aas protein for therapeutic applications?

Designing inhibitors specific to the bifunctional activities of the aas protein requires a sophisticated structure-based approach. Based on strategies used for other bifunctional enzymes, researchers should consider:

• Active Site Mapping: Determine the precise architecture of both active sites using X-ray crystallography or cryo-EM, potentially following approaches used for other bifunctional enzymes like alanine racemase .

• Fragment-Based Drug Design: Screen small molecule libraries against each active site independently to identify fragments with high binding affinity and specificity.

• Dual-Target Inhibitor Design: Two approaches are possible:

  • Design single molecules that simultaneously inhibit both functions

  • Develop separate inhibitors for each function and assess synergistic effects

• Allosteric Inhibition: Target non-catalytic sites that influence both functions through conformational changes.

• Structure-Activity Relationship (SAR) Studies: Systematically modify lead compounds to optimize:

  • Binding affinity

  • Selectivity over host homologs

  • Pharmacokinetic properties

The inhibitor design process should incorporate molecular dynamics simulations to predict binding energies and conformational changes. Validation of inhibitors should include both in vitro enzyme assays and cellular models of infection to confirm target engagement and efficacy.

What are common challenges in expressing and purifying active recombinant aas protein, and how can they be addressed?

Researchers frequently encounter several challenges when working with recombinant Salmonella choleraesuis Bifunctional protein aas. Here are systematic approaches to address each issue:

Additionally, for storage and handling, avoid repeated freeze-thaw cycles by storing working aliquots at 4°C for up to one week and keep long-term stocks at -20°C/-80°C with 50% glycerol .

How can researchers overcome the challenges of studying the distinct catalytic functions of aas protein independently?

Studying the distinct catalytic functions of bifunctional proteins like aas independently requires sophisticated experimental approaches. Based on methodologies applied to other bifunctional enzymes:

• Domain Separation and Expression:

  • Perform bioinformatic analysis to predict domain boundaries

  • Express individual domains separately to study isolated functions

  • Create chimeric proteins with domains from homologous proteins to test functional compatibility

• Site-Directed Mutagenesis:

  • Identify catalytic residues specific to each function through sequence alignment with single-function homologs

  • Create point mutations that selectively inactivate one function while preserving the other

  • Validate functional changes through specific enzyme assays for each activity

• Selective Inhibition:

  • Identify inhibitors specific to one function but not the other

  • Use these inhibitors to study the remaining function in isolation

  • Develop assay conditions that favor one activity over the other

• Structural Analysis:

  • Use X-ray crystallography or cryo-EM to capture the protein in different conformational states

  • Perform molecular dynamics simulations to understand the conformational changes associated with each function

  • Apply hydrogen-deuterium exchange mass spectrometry to identify regions with different dynamics related to each function

These approaches would follow similar methodologies to those used for studying other bifunctional enzymes like alanine racemase, where researchers successfully differentiated between racemization and ligation functions .

What methodological approaches can help resolve contradictory experimental results when studying aas protein interactions with host systems?

When facing contradictory experimental results regarding aas protein interactions with host systems, researchers should implement a systematic troubleshooting approach:

• Standardize Experimental Conditions:

  • Ensure consistent protein preparation methods across experiments

  • Control for batch-to-batch variations with appropriate quality control measures

  • Document and control environmental variables (temperature, pH, buffer composition)

• Employ Multiple Detection Methods:

  • Validate protein-protein interactions using complementary techniques:

    • Co-immunoprecipitation

    • Surface plasmon resonance

    • Yeast two-hybrid assays

    • FRET or BRET assays

  • Each method has different strengths and limitations that may explain contradictory results

• Consider Cellular Context:

  • Test interactions in multiple cell types relevant to Salmonella infection

  • Examine the influence of cellular activation states

  • Assess the impact of other bacterial factors that may be present during infection

• Perform Dose-Response and Time-Course Studies:

  • Contradictory results often stem from differences in protein concentration or timing

  • Systematically vary protein concentrations and exposure times

  • Generate comprehensive dose-response and time-course data

• Develop Appropriate Controls:

  • Include inactive mutants of aas protein

  • Use closely related proteins that lack the specific functions being studied

  • Include host cells with knocked-out potential interaction partners

This multifaceted approach draws on techniques similar to those used for studying other bacterial effector proteins like SopD, where researchers identified both activating and inhibitory effects on host signaling pathways depending on experimental conditions .

What emerging technologies might advance our understanding of the bifunctional mechanisms of aas protein?

Several cutting-edge technologies show promise for elucidating the bifunctional mechanisms of proteins like Salmonella choleraesuis aas:

• Cryo-Electron Microscopy (Cryo-EM):

  • Captures proteins in native-like environments without crystallization

  • Reveals conformational ensembles representing different functional states

  • Can visualize the protein during catalytic cycles at near-atomic resolution

• Time-Resolved X-ray Crystallography:

  • Captures structural changes during catalysis

  • Provides insights into the coordination between different functional domains

  • Reveals transitional states that may explain the bifunctional mechanism

• Single-Molecule FRET:

  • Monitors conformational changes in real-time

  • Tracks the dynamic switching between different functional states

  • Identifies potential allosteric communication between active sites

• AlphaFold2 and Deep Learning Approaches:

  • Predicts structures with high accuracy, including functionally relevant conformational states

  • Models protein-substrate interactions for each catalytic function

  • Simulates conformational changes associated with functional switching

• Integrative Structural Biology:

  • Combines multiple experimental approaches (X-ray, NMR, SAXS, EM) with computational modeling

  • Provides comprehensive understanding of structure-function relationships

  • Resolves contradictions between different experimental approaches

These technologies could overcome the limitations of traditional structural biology approaches that have been applied to other bifunctional enzymes like alanine racemase , providing unprecedented insights into the dynamic nature of bifunctional proteins.

How might CRISPR/Cas9 genome editing be applied to study the physiological roles of aas protein in Salmonella choleraesuis?

CRISPR/Cas9 genome editing offers powerful approaches for investigating the physiological roles of aas protein in Salmonella choleraesuis:

• Precise Gene Knockout:

  • Generate complete aas gene deletions to assess effects on bacterial viability and virulence

  • Create conditional knockouts for essential genes using inducible systems

  • Introduce specific point mutations to disable one function while preserving the other

• Domain-Specific Modifications:

  • Selectively delete or modify individual functional domains

  • Replace domains with homologous sequences from related proteins

  • Introduce epitope or fluorescent tags for tracking protein localization

• Regulatory Element Editing:

  • Modify promoters to alter expression levels

  • Disrupt or enhance regulatory elements to understand expression patterns during infection

  • Create reporter fusions to monitor expression under different conditions

• Host Cell Engineering:

  • Edit potential host target genes (identified through interaction studies)

  • Create reporter cell lines to monitor effects of aas protein on host signaling

  • Generate cell lines with modified potential interaction partners

Similar CRISPR/Cas9 approaches have been successfully applied to study other bacterial proteins like Rab8, which was edited to understand its role in Salmonella-induced signaling pathways . These genome editing techniques provide precise tools for dissecting the complex functions of bifunctional proteins in both bacterial and host contexts.

What are the potential applications of engineering modified versions of aas protein for biotechnology and basic research?

The bifunctional nature of the Salmonella choleraesuis aas protein presents numerous opportunities for engineering applications in biotechnology and research:

• Designer Bifunctional Enzymes:

  • Create chimeric proteins with novel combinations of enzymatic activities

  • Optimize catalytic efficiencies for specific biotechnological processes

  • Develop switchable enzymes that respond to environmental cues

• Vaccine Development:

  • Engineer attenuated Salmonella strains with modified aas for improved safety and immunogenicity

  • Use the protein as a carrier for heterologous antigens, similar to approaches with recombinant attenuated Salmonella Typhimurium expressing heterologous O-antigens

  • Develop subunit vaccines targeting conserved epitopes from aas

• Protein Scaffolds:

  • Utilize the bifunctional architecture as a scaffold for protein engineering

  • Create fusion proteins with novel combinations of activities

  • Develop protein-based biosensors that exploit the dual functionality

• Drug Discovery Platforms:

  • Engineer the protein for high-throughput screening of potential inhibitors

  • Develop assay systems to identify compounds that selectively inhibit one function

  • Create reporter systems for monitoring protein-protein interactions in vivo

• Synthetic Biology Applications:

  • Incorporate the bifunctional protein into synthetic metabolic pathways

  • Design genetic circuits that exploit the dual functionality for complex cellular computations

  • Create bacterial biosensors for environmental monitoring

These applications draw on approaches similar to those used for other bifunctional proteins and recombinant Salmonella systems, where researchers have successfully engineered bacteria to express heterologous antigens for vaccine development and studied complex enzymatic systems for biotechnological applications .