Recombinant Shigella dysenteriae serotype 1 Universal stress protein B (uspB)

What is Universal stress protein B (uspB) in Shigella dysenteriae serotype 1?

Universal stress protein B (uspB) is a stress-responding protein expressed by Shigella dysenteriae serotype 1 that helps the bacterium combat environmental stressors. Similar to the better-characterized Universal stress protein A (uspA) in E. coli, uspB likely plays a role in bacterial adaptation to adverse conditions such as nutrient limitation, oxidative stress, and exposure to antimicrobial agents . The full-length protein consists of 111 amino acids and has been successfully expressed as a recombinant protein with an N-terminal His tag in E. coli expression systems . uspB is part of a larger stress response system that enables S. dysenteriae to survive hostile host environments during infection.

What is the amino acid sequence of S. dysenteriae serotype 1 uspB?

The full amino acid sequence of Shigella dysenteriae serotype 1 Universal stress protein B (uspB) is:

MISTVALFWALCVVCIVNMARYFSSLRALLVVLRNCDPLLYQYVDGGGFFTSHGQPNKQVRLVWYIYAQRYRDHHDDEFIRRCERVRRQFILTSALCGLVVVSLIALMIWH

This 111-amino acid sequence contains regions typical of stress proteins and likely contributes to the protein's functional properties in responding to environmental stressors. The protein has been assigned the UniProt ID Q32AW3, and its gene is annotated as SDY_3568 in some genomic databases .

How does uspB expression change under different stress conditions?

While specific data on uspB expression dynamics in S. dysenteriae is limited in the provided search results, research on related universal stress proteins suggests that uspB expression is likely upregulated in response to various stressors. In E. coli, universal stress proteins are known to be triggered by adverse environmental factors including starvation, heat, acid exposure, oxidative stress, heavy metals, and antibiotics . Similar to its homologs, S. dysenteriae uspB expression patterns likely vary depending on the specific environmental stressors encountered and may differ between various infection sites . Transcriptomic studies have shown that S. dysenteriae demonstrates differential gene expression profiles when isolated from different anatomical locations during infection, suggesting that uspB may be differentially regulated depending on the specific microenvironment the bacterium encounters .

What are the optimal conditions for recombinant expression of S. dysenteriae serotype 1 uspB?

For recombinant expression of S. dysenteriae serotype 1 uspB, E. coli expression systems have proven successful . While detailed optimization parameters were not specified in the search results, general principles for recombinant protein expression apply. The most common approach involves:

• Vector selection: Vectors containing strong inducible promoters (like T7) and appropriate fusion tags (such as His-tag) facilitate expression and subsequent purification.

• E. coli strain selection: BL21(DE3) or similar strains optimized for protein expression are recommended.

• Induction conditions: Typically, induction with IPTG at 0.1-1.0 mM when culture reaches mid-log phase (OD600 ~0.6-0.8).

• Growth temperature: Lower temperatures (16-25°C) often improve soluble protein yield for stress proteins.

• Growth media: Enriched media like LB or 2XYT supplemented with appropriate antibiotics.

Expression yields can be verified through SDS-PAGE analysis, with successful expression protocols yielding protein purity greater than 90% .

What purification strategy is most effective for isolating recombinant S. dysenteriae serotype 1 uspB?

For His-tagged recombinant S. dysenteriae serotype 1 uspB, immobilized metal affinity chromatography (IMAC) is the most effective initial purification method . A typical purification protocol would include:

• Cell lysis: Using sonication or pressure-based disruption in a suitable buffer (often Tris/PBS-based, pH 8.0).

• IMAC purification: Using Ni-NTA or similar resin with appropriate imidazole gradients for washing and elution.

• Secondary purification: Size exclusion chromatography to achieve higher purity if required.

• Quality control: SDS-PAGE and Western blotting to confirm purity (>90% is typically achievable).

• Storage: Lyophilization or storage in Tris/PBS-based buffer with 6% trehalose at pH 8.0, with the addition of 5-50% glycerol for long-term storage at -20°C/-80°C .

This approach typically yields high-purity protein suitable for downstream functional and structural studies.

How can researchers prevent aggregation of recombinant uspB during expression and purification?

Preventing aggregation of recombinant S. dysenteriae uspB requires careful optimization of several parameters:

• Expression temperature optimization: Lower temperatures (16-20°C) often reduce inclusion body formation.

• Co-expression with chaperones: Molecular chaperones like GroEL/ES can aid proper folding.

• Buffer optimization: Inclusion of mild solubilizing agents (0.1-0.5% Triton X-100 or low concentrations of urea) in lysis buffers.

• Additive screening: Addition of amino acids (arginine, glutamic acid) or osmolytes (glycerol, sucrose) to stabilize the protein.

• pH optimization: Testing different pH conditions to identify optimal stability range.

For storage and reconstitution, avoiding repeated freeze-thaw cycles is critical, and reconstitution should be performed in deionized sterile water to a concentration of 0.1-1.0 mg/mL with glycerol added to a final concentration of 5-50% . When handling lyophilized protein, brief centrifugation prior to opening the vial helps bring contents to the bottom, reducing loss of material.

How does uspB contribute to Shigella dysenteriae serotype 1 pathogenesis?

While the search results don't provide direct evidence of uspB's specific role in S. dysenteriae pathogenesis, insights can be gained from studies of universal stress proteins in related bacteria. Universal stress proteins are critically involved in bacterial adaptation to environmental stressors, which is essential for pathogenesis .

In the context of S. dysenteriae infection:

• Stress adaptation: uspB likely helps the bacterium survive the acidic environment of the stomach and the oxidative burst of host immune cells.

• Virulence regulation: Stress proteins can influence the expression of virulence factors. S. dysenteriae shows differential gene expression patterns between primary infection sites and invasive locations .

• Persistence: By enabling adaptation to nutrient limitation and other stressors in the host environment, uspB may contribute to bacterial persistence.

Transcriptomic studies have shown that S. dysenteriae differentially expresses genes involved in invasion and virulence depending on its location within the host, suggesting that stress response proteins like uspB might play context-dependent roles during infection progression .

What experimental approaches can be used to study uspB function in vitro?

Multiple complementary approaches can be employed to characterize uspB function in vitro:

• Protein-protein interaction studies:

  • Yeast two-hybrid screening

  • Pull-down assays using His-tagged recombinant uspB

  • Surface plasmon resonance (SPR) to identify binding partners

• Structural characterization:

  • X-ray crystallography

  • NMR spectroscopy

  • Circular dichroism to analyze secondary structure

• Functional assays:

  • Stress resistance assays using recombinant uspB in cell-free systems

  • ATP binding/hydrolysis assays

  • Chaperone activity assays

• Comparative studies:

  • Analysis alongside known universal stress proteins like uspA

  • Comparison of activities across different Shigella species and related enterobacteria

These methods can provide complementary insights into uspB's molecular function and its role in the stress response of S. dysenteriae.

How does uspB compare structurally and functionally to uspA in Shigella and related enterobacteria?

While detailed comparative analyses of uspB and uspA in Shigella are not provided in the search results, some insights can be derived from the available information:

• Sequence comparison: uspB in S. dysenteriae serotype 1 consists of 111 amino acids , whereas uspA proteins are typically larger. In related species, sequence variations have been observed - for example, uspA in S. sonnei shows 17 bp mismatches compared to E. coli K-12, with 8 mismatches within the structural gene .

• Functional distinctions:

  • Both proteins respond to environmental stress, but may be triggered by different stimuli

  • uspA is well characterized in responding to starvation, heat, acid, oxidants, heavy metals, and antibiotics in E. coli

  • uspB may have more specialized functions in specific stress conditions

• Evolutionary conservation:

  • Studies of uspA showed that while mismatches between E. coli K-12 and both E. coli O157:H7 and S. sonnei resulted in an alanine to arginine substitution at position 140, mismatches between S. sonnei and E. coli O157:H7 were silent mutations

  • Similar comparative analysis of uspB across species could reveal its evolutionary conservation pattern

A comprehensive comparative analysis would require additional structural studies and functional characterization of both proteins across multiple species.

What are the most effective methods for studying uspB expression patterns during Shigella infection?

Several complementary approaches can be used to study uspB expression during Shigella infection:

• Transcriptomic analysis:

  • RNA-Seq to compare gene expression between bacteria isolated from different infection sites, as demonstrated in studies comparing S. dysenteriae from stool and blood samples

  • qRT-PCR for targeted quantification of uspB expression under various conditions

• Reporter systems:

  • Construction of uspB promoter-reporter fusions (e.g., with GFP or luciferase) to monitor expression in real-time

  • Dual fluorescent protein reporters to study uspB regulation dynamics

• Protein detection:

  • Western blotting with anti-uspB antibodies

  • Immunofluorescence microscopy to visualize uspB in infected tissues

  • Mass spectrometry-based proteomics to quantify protein levels

• Animal models:

  • Using gnotobiotic piglet models, which have been successfully employed for studying S. dysenteriae infections

  • Isolation of bacteria from different anatomical sites for comparative analysis

These methods can provide comprehensive insights into how uspB expression changes during different stages of infection and in response to varying host microenvironments.

How can researchers design effective knockout or knockdown experiments to study uspB function?

To effectively study uspB function through gene disruption approaches:

• CRISPR-Cas9 gene editing:

  • Design guide RNAs targeting uspB

  • Use homology-directed repair to introduce specific mutations

  • Confirm edits by sequencing

• Traditional knockout methods:

  • Homologous recombination with antibiotic resistance cassettes

  • Allelic exchange vectors

  • P1 transduction if applicable

• Conditional approaches:

  • Inducible antisense RNA expression

  • Temperature-sensitive mutants

  • Degradation tag systems for protein-level control

• Validation strategies:

  • RT-PCR and Western blotting to confirm knockdown

  • Complementation studies to verify phenotype specificity

  • Whole genome sequencing to check for off-target effects

• Phenotypic assessment:

  • Stress sensitivity assays (acid, oxidative, nutrient limitation)

  • Invasion assays using cell culture models

  • Competition assays with wild-type strains

  • In vivo virulence studies using appropriate animal models like gnotobiotic piglets

When interpreting results, it's important to consider potential compensatory mechanisms, as other stress response proteins might partially compensate for uspB absence.

What model systems are most appropriate for studying uspB function in the context of Shigella pathogenesis?

Several model systems can be employed to study uspB function in Shigella pathogenesis:

• In vitro cell culture models:

  • Intestinal epithelial cell lines (Caco-2, HT-29)

  • Macrophage cell lines (THP-1, RAW264.7) to study persistence in immune cells

  • Organoid cultures for more physiologically relevant intestinal models

• Ex vivo systems:

  • Human intestinal tissue explants

  • Polarized epithelial cell systems to model intestinal barrier

• Animal models:

  • Gnotobiotic piglets: Proven effective for studying S. dysenteriae infection and proteome analysis in vivo

  • Mouse models: Including streptomycin-treated mice for studying intestinal colonization

  • Guinea pig keratoconjunctivitis model: Useful for assessing invasion and inflammatory response

• Comparative systems:

  • Side-by-side analysis in multiple hosts to identify host-specific aspects of uspB function

  • Comparison of uspB function across different Shigella species and serotypes

Each model offers unique advantages, with gnotobiotic piglets being particularly valuable as they allow for isolation of bacterial proteins directly from infected tissues for comprehensive proteome analysis during infection .

How can high-throughput screening be optimized to identify inhibitors of uspB function?

Optimizing high-throughput screening for uspB inhibitors requires a multi-faceted approach:

• Assay development:

  • Enzymatic assays if uspB exhibits measurable catalytic activity

  • Thermal shift assays to identify compounds that bind and stabilize uspB

  • FRET-based assays to detect uspB interactions with binding partners

  • Cell-based reporter systems to monitor uspB activity in vivo

• Compound library selection:

  • Natural product libraries (particularly antimicrobial compounds)

  • Fragment-based libraries for initial hit identification

  • Focused libraries based on known inhibitors of related stress proteins

  • Repurposing libraries of clinically approved drugs

• Screening strategy:

  • Primary screening at single concentration (10-20 μM typical)

  • Dose-response confirmation of hits

  • Counter-screening against related proteins to assess selectivity

  • Secondary functional assays in bacterial cultures

• Data analysis and hit validation:

  • Statistical methods to identify true positives (Z-factor optimization)

  • Structure-activity relationship studies for hit optimization

  • Binding confirmation via biophysical methods (ITC, SPR, NMR)

  • Validation in infection models

• Practical considerations:

  • Stabilization of purified recombinant uspB during screening

  • Optimizing buffer conditions to minimize false positives

  • Quality control measures for consistent protein activity

This approach can identify chemical probes for studying uspB function and potentially novel antimicrobial agents targeting stress response systems in Shigella.

What structural characteristics of uspB can be leveraged for rational drug design?

Although detailed structural information about S. dysenteriae uspB is not provided in the search results, rational drug design approaches can be developed based on:

• Sequence-based predictions:

  • The full amino acid sequence (MISTVALFWALCVVCIVNMARYFSSLRALLVVLRNCDPLLYQYVDGGGFFTSHGQPNKQVRLVWYIYAQRYRDHHDDEFIRRCERVRRQFILTSALCGLVVVSLIALMIWH) can be used for structural modeling

  • Identification of conserved motifs through alignment with other universal stress proteins

  • Prediction of functional domains and active sites

• Homology modeling:

  • Using crystal structures of related universal stress proteins as templates

  • Validation of models through molecular dynamics simulations

  • Refinement based on experimental data

• Targetable features:

  • Potential ligand binding pockets

  • Protein-protein interaction interfaces

  • Allosteric regulatory sites

  • Post-translational modification sites

• Virtual screening approaches:

  • Structure-based virtual screening against modeled binding sites

  • Pharmacophore modeling based on predicted functional motifs

  • Fragment-based design targeting key structural elements

• Experimental validation:

  • Mutagenesis studies to confirm importance of predicted structural features

  • Biophysical assays to validate binding of designed compounds

  • X-ray crystallography or cryo-EM to determine actual structure

This approach can guide the development of selective inhibitors targeting uspB function in S. dysenteriae.

How does differential expression of uspB contribute to Shigella dysenteriae serotype 1 pathogenesis across different infection sites?

Research on differential gene expression in S. dysenteriae provides insights into how stress response proteins like uspB may contribute to pathogenesis across different infection sites:

• Site-specific adaptation:

  • S. dysenteriae demonstrates differential gene expression profiles when isolated from primary infection sites (intestinal) versus invasive locations (bloodstream)

  • This suggests that uspB may be differentially regulated depending on the specific microenvironment

• Stress response coordination:

  • In the intestinal environment, S. dysenteriae must cope with acid stress, requiring proteins like GadB and AdiA for pH homeostasis

  • Protein disaggregation chaperones (HdeA, HdeB, ClpB) show increased abundance in vivo, suggesting coordinated stress responses

  • uspB may work in concert with these systems in a site-specific manner

• Research findings table:

• Methodological approaches:

  • Transcriptomic analysis comparing isolates from different sites has revealed that genes involved in invasion are highly expressed at primary infection sites

  • Similar approaches can be applied specifically to uspB to understand its site-specific expression patterns

Understanding these differential expression patterns could inform targeted therapeutic approaches that disrupt pathogen adaptation to specific host environments.

What are the current limitations in studying uspB function and how might they be overcome?

Several challenges exist in studying S. dysenteriae uspB function:

• Technical limitations:

  • Difficulty in maintaining stable recombinant protein (current protocols recommend avoiding repeated freeze-thaw cycles)

  • Limited structural data specific to uspB

  • Challenges in mimicking the in vivo intracellular environment in vitro

• Knowledge gaps:

  • Incomplete understanding of the specific stimuli that trigger uspB expression

  • Limited data on protein-protein interactions involving uspB

  • Uncertain relationship between uspB and virulence mechanisms

• Methodological challenges:

  • Difficulty in isolating sufficient bacterial proteins directly from infection sites

  • Limitations of current animal models in replicating human shigellosis

  • Challenges in real-time monitoring of uspB expression during infection

• Suggested approaches to overcome limitations:

  • Development of improved protein stabilization methods

  • Creation of better reporter systems for monitoring uspB expression in vivo

  • Application of single-cell techniques to study uspB expression heterogeneity

  • Integration of multi-omics approaches (transcriptomics, proteomics, metabolomics)

  • Development of in vitro systems that better mimic the intracellular environment

These advances could significantly enhance our understanding of uspB function in S. dysenteriae pathogenesis.

How can computational approaches enhance our understanding of uspB function and regulation?

Computational approaches offer powerful tools to advance understanding of uspB:

• Sequence-based analyses:

  • Phylogenetic analysis to understand evolutionary relationships among uspB proteins

  • Identification of conserved regulatory elements in uspB promoter regions

  • Prediction of post-translational modifications and their functional impact

• Structural bioinformatics:

  • Homology modeling to predict uspB structure

  • Molecular dynamics simulations to study protein dynamics

  • Protein-protein interaction prediction

  • Virtual ligand screening to identify potential binding partners

• Systems biology approaches:

  • Genome-scale metabolic modeling to predict the role of uspB in cellular metabolism

  • Network analysis to place uspB in the context of stress response pathways

  • Integration of transcriptomic data to identify co-regulated genes

  • Machine learning to predict conditions affecting uspB expression

• Comparative genomics:

  • Analysis of uspB conservation across Shigella strains and related enterobacteria

  • Identification of strain-specific variations that might affect function

  • Similar to studies comparing uspA between S. sonnei and E. coli strains

These computational approaches can generate testable hypotheses and guide experimental design, accelerating progress in understanding uspB biology.

What potential exists for targeting uspB in novel antimicrobial development strategies?

Universal stress proteins like uspB represent promising targets for novel antimicrobial development:

• Rationale for targeting uspB:

  • As a stress response protein, uspB likely contributes to bacterial persistence during infection

  • Targeting stress response systems may enhance effectiveness of existing antibiotics

  • S. dysenteriae isolates have shown resistance to multiple antibiotics (dhfr1A, sulII, blaOXA, blaCTX-M-1, qnrS) , necessitating novel targets

• Potential therapeutic strategies:

  • Direct inhibition of uspB function through small molecule inhibitors

  • Disruption of uspB interactions with other stress response proteins

  • Antisense strategies to reduce uspB expression

  • CRISPR-Cas delivery systems targeting uspB gene

• Combination approaches:

  • Pairing uspB inhibitors with conventional antibiotics

  • Targeting multiple stress response proteins simultaneously

  • Combining with virulence inhibitors targeting type III secretion system components

• Challenges and considerations:

  • Need for selectivity to avoid targeting human proteins

  • Potential for resistance development

  • Delivery challenges, particularly for intracellular bacteria

  • Requirement for thorough validation in relevant infection models

• Promising approaches:

  • Structure-based drug design once uspB structure is determined

  • Phenotypic screening using stress conditions relevant to infection

  • Repurposing of existing drugs with potential anti-stress response activity

By targeting bacterial adaptation mechanisms rather than essential functions, anti-uspB therapies might impose less selective pressure for resistance development while enhancing host clearance of the pathogen.