Recombinant Brucella melitensis biotype 1 Putative peptide permease protein BMEII0861 (BMEII0861)

What expression systems are most effective for producing recombinant BMEII0861 protein?

Current research indicates that E. coli is the most commonly used and effective expression system for recombinant BMEII0861 production. The protein has been successfully expressed as a fusion protein with an N-terminal His tag in E. coli .

When designing expression constructs, researchers should consider:

• Expression vector selection: pCold vectors have been used successfully for other Brucella proteins and may be suitable for BMEII0861

• Tag placement: N-terminal His-tagging has been demonstrated to be effective

• Codon optimization: Adaptation to E. coli codon usage may improve expression yield

• Expression conditions: Optimal temperature, IPTG concentration, and induction time should be determined empirically

It's important to note that different expression systems may yield proteins with varying immunological properties. A comparative study of other Brucella recombinant proteins expressed in eukaryotic versus prokaryotic systems showed significant differences in protective effects against Brucella melitensis . Therefore, researchers should consider testing multiple expression systems when studying immunological properties of BMEII0861.

Purification Protocol:

Based on current research practices for similar Brucella proteins, the following purification approach is recommended:

• Affinity chromatography: For His-tagged BMEII0861, Ni-NTA column purification is the primary method

• Further purification: Size exclusion chromatography may be employed to achieve >90% purity as determined by SDS-PAGE

• Buffer optimization: A Tris/PBS-based buffer, 6% Trehalose, pH 8.0 has been demonstrated to be effective for final formulation

Storage Recommendations:

For optimal stability and activity preservation:

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

• Long-term storage:

  • Store at -20°C/-80°C upon receipt

  • Aliquoting is necessary to avoid repeated freeze-thaw cycles

  • Addition of 5-50% glycerol (final concentration) is recommended before freezing

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

Researchers should note that repeated freezing and thawing significantly impacts protein stability and should be avoided .

In Vitro Experimental Designs:

• Protein-Substrate Interaction Studies:

  • Substrate binding assays to identify transported peptides

  • Molecular docking analysis (similar to the approach used for BME_RS12880)

• Cell Culture Models:

  • RAW 264.7 macrophage infection model to assess intracellular survival

  • HeLa cell invasion assays to evaluate bacterial internalization

  • Acidic stress survival assays to assess contribution to stress resistance

• Gene Expression Analysis:

  • qRT-PCR to evaluate expression under different conditions

  • Microarray or RNA-Seq for global transcriptomic profiling

In Vivo Experimental Designs:

• Mouse Infection Models:

  • BALB/c mouse model (most commonly used)

  • Spleen bacterial load assessment at defined timepoints post-infection

  • Evaluation of bacterial clearance kinetics

• Mutational Analysis:

  • Generation of BMEII0861 deletion mutants

  • Complementation studies to confirm phenotypes

  • Competitive infection assays (wild-type vs. mutant)

Statistical Design Considerations:

Based on experimental design principles , researchers should consider:

• Randomized Complete Block Design (RCBD) for experiments with potential confounding variables

• Factorial designs when evaluating multiple factors (e.g., gene deletion × stress condition)

• Sample size calculation to ensure adequate statistical power

• Appropriate controls including wild-type strains and complemented mutants

For statistical analysis, the following approaches are recommended:

• Analysis of variance (ANOVA) for comparing multiple groups

• Student's t-test for two-group comparisons

• Expression of results as mean ± standard deviation

• Consideration of p < 0.05 as statistically significant

How does BMEII0861 compare structurally and functionally with other ABC transporters in Brucella?

BMEII0861 belongs to the broader family of ABC transporters in Brucella that can be categorized based on function and structure. Comparative analysis shows:

Structural Comparison:

BMEII0861 shares the core structural features of ABC transporters, including:

• Transmembrane domains that form the channel for substrate translocation

• Membership in the binding-protein-dependent transport system permease family

Functional Classification:

Within the ABC transporter systems of Brucella, BMEII0861 is classified in the peptide transport systems. The following table shows different ABC transporter systems identified in Brucella melitensis:

Table derived from information in search results

Evolutionary Conservation:

Comparative genomics analysis of Brucella species reveals that ABC transporters are part of the core genome, with most systems being highly conserved across strains and species . This conservation suggests essential roles in bacterial physiology beyond species-specific adaptations.

Methodological Approaches for Mutation Analysis:

The following approaches have been used to study the effects of ABC transporter mutations:

• Gene deletion strategies:

  • Targeted deletion of individual components

  • Deletion of entire operons

  • Generation of complemented strains to confirm phenotypes

• Phenotypic characterization:

  • Growth curve analysis under various conditions

  • Sensitivity to antimicrobial peptides and stress conditions

  • Cell invasion and intracellular replication assays

  • Mouse infection models with bacterial load assessment

Based on these findings, mutations in BMEII0861 would likely impact B. melitensis virulence, particularly under stress conditions or during host infection, while potentially having minimal effects on growth in standard laboratory media.

What is the potential of recombinant BMEII0861 as a component in subunit vaccines against brucellosis?

While BMEII0861 specifically has not been extensively studied as a vaccine candidate, research on other recombinant Brucella proteins provides valuable insights into its potential:

Promising Indicators for BMEII0861 as a Vaccine Component:

• Membrane location: As a transmembrane protein, BMEII0861 is likely exposed to the host immune system during infection

• Conservation: ABC transporters are generally well-conserved across Brucella strains

• Role in virulence: Its potential contribution to survival within hosts suggests it may be a meaningful target for protective immunity

Strategies Based on Similar Recombinant Protein Vaccines:

Research on other Brucella recombinant proteins has demonstrated:

• Combined Subunit Vaccines (CSVs):

  • Combinations of multiple recombinant proteins show superior protection compared to individual proteins

  • A combination of L7/L12, Omp16, Omp19, and Omp28 provided significant protection against B. abortus infection

• Adjuvant Selection:

  • Natural adjuvants like Taishan Pinus massoniana pollen polysaccharides (TPPPS) enhance immune responses to recombinant Brucella proteins

• Immunological Assessment Methods:

  • Antibody levels

  • Spleen lymphocyte proliferation

  • Percentages of CD4+ and CD8+ T cells

  • Cytokine secretion profiles

  • Protection against challenge with virulent strains

Experimental Approach for Testing BMEII0861 as a Vaccine Candidate:

• Expression system selection: Compare eukaryotic vs. prokaryotic expression systems for optimal immunogenicity

• Immunization protocols: Multiple doses (typically three) with appropriate adjuvants

• Challenge studies: Assessment of protection against virulent Brucella melitensis

• Protection measurement: CFU counting in spleens after challenge (expressed as log₁₀ reduction)

Given its characteristics, BMEII0861 could be a valuable addition to multi-component subunit vaccines, particularly when combined with established immunogenic proteins like Omp10, Omp28, and L7/L12 .

How is the expression of BMEII0861 regulated in response to environmental stressors?

While the specific regulation of BMEII0861 expression is not directly addressed in the search results, studies on ABC transporters in Brucella under various environmental conditions provide relevant insights:

Regulation Patterns of ABC Transporters:

• Growth Phase-Dependent Regulation:

  • B. melitensis exhibits differential gene expression between growth phases

  • During late-log phase, 414 genes (91%) were up-regulated compared to stationary phase

  • These included genes associated with membrane transport (56 genes)

• Stress-Responsive Regulation:

  • Under osmotic stress conditions, ABC transporters are significantly enriched in differentially expressed genes

  • Transcriptome profiling identified specific ABC transporters as essential for osmotic stress response in biofilms

• Environmental Sensing:

  • Expression of similar systems (YejABEF) is induced by exposure to antimicrobial peptides like polymyxin B

  • This suggests that these transport systems respond to the presence of their substrates or to relevant stress conditions

Regulatory Mechanisms:

The regulation of ABC transporters in Brucella likely involves:

• Transcription Factors:

  • Several transcription factor families are identified in B. melitensis, including:

    • LuxR and AraC (involved in positive regulation)

    • DeoR and MerR (involved in repression)

    • IclR and LysR families (can be activators or repressors)

• Alternative Sigma Factors:

  • Sigma 32 factor (BMEI0280) - upregulated in stationary phase, involved in general stress response

  • Sigma 54 factor (rpoN, BMEI1789) - upregulated in late-log phase, involved in nitrogen/carbon utilization and energy metabolism

• Small RNA Regulation:

  • Small RNA regulation is implicated in biofilm responses to stress conditions

Based on these patterns, BMEII0861 expression is likely dynamically regulated in response to environmental conditions, particularly those that require peptide transport or antimicrobial peptide resistance.

What are the immunological properties of recombinant BMEII0861 and its interactions with host immune responses?

While the specific immunological properties of BMEII0861 are not directly described in the search results, insights can be drawn from studies on other recombinant Brucella proteins and ABC transporters:

Potential Immunological Properties:

• Antigenicity:

  • As a membrane protein, BMEII0861 likely contains epitopes recognizable by the host immune system

  • Similar Brucella proteins have demonstrated ability to induce both humoral and cell-mediated immune responses

• Immune Response Patterns:
  Based on studies with other Brucella recombinant proteins, BMEII0861 may induce:

  • Antibody production (humoral immunity)

  • T-cell responses, particularly CD4+ and CD8+ T cell activation

  • Cytokine secretion profiles consistent with protective immunity

Assessment Methodologies:

To characterize the immunological properties of recombinant BMEII0861, researchers typically measure:

• Antibody Responses:

  • IgG titers in serum following immunization

  • Isotype distribution (IgG1, IgG2a, etc.) to determine Th1/Th2 balance

• Cell-Mediated Immunity:

  • Spleen lymphocyte proliferation in response to antigen stimulation

  • Percentages of CD4+ and CD8+ T cells

  • Cytokine secretion profiles (IFN-γ, IL-2, IL-4, IL-10, etc.)

• Protective Efficacy:

  • Challenge with virulent Brucella strains

  • Measurement of bacterial load in spleen (expressed as log₁₀ CFU)

  • Calculation of protection units (mean log₁₀ CFU of control group minus log₁₀ CFU of vaccinated group)

Adjuvant Considerations:

The choice of adjuvant significantly impacts the immune response to recombinant proteins:

• Natural adjuvants like Taishan Pinus massoniana pollen polysaccharides (TPPPS) have shown effectiveness in enhancing immune responses to Brucella recombinant proteins

• Adjuvant selection should be optimized based on the desired immune response pattern (Th1 vs. Th2)

What research challenges exist in studying BMEII0861 function and expression?

Researchers face several significant challenges when investigating BMEII0861:

Technical Challenges:

• Membrane Protein Expression:

  • As a transmembrane protein, BMEII0861 may be difficult to express in soluble, correctly folded form

  • Optimization of expression conditions may require extensive troubleshooting

  • Detergent selection for solubilization needs careful consideration

• Functional Characterization:

  • Identifying specific peptide substrates requires specialized transport assays

  • Difficulty in establishing direct links between transport function and virulence phenotypes

  • Potential functional redundancy with other transporters may mask phenotypes in single gene mutants

• Biosafety Considerations:

  • Brucella melitensis is a BSL-3 pathogen, requiring specialized containment facilities

  • Live bacterial manipulation poses safety risks that complicate experimental design

  • Recombinant protein work requires appropriate biosecurity screening

Methodological Challenges:

• Experimental Design:

  • Selection of appropriate controls for mutational studies

  • Designing experiments that isolate specific function from compensatory mechanisms

  • Balancing between in vitro simplicity and in vivo relevance

• Data Analysis and Reporting:

  • Proper statistical analysis and reporting of results

  • Presenting numerical data in technically appropriate terms

  • Expressing data consistently as mean/median ± standard deviation with appropriate ranges

• Reproducibility Issues:

  • Variability in expression systems and purification methods

  • Consistency in infection models and immune response measurements

  • Standardization of protocols across different research groups

Interpretation Challenges:

• Functional Redundancy:

  • Multiple peptide transporters may have overlapping functions

  • Compensatory mechanisms may mask phenotypes in single mutants

  • Distinguishing specific contributions from general ABC transporter functions

• Translating in vitro findings to in vivo significance:

  • Connecting molecular mechanisms to pathogenesis in animal models

  • Extrapolating from model systems to natural infection processes

  • Integrating protein-level findings with systems biology perspectives

What future research directions should be prioritized for understanding BMEII0861's role in Brucella biology?

Based on current knowledge gaps and emerging research trends, several priority areas for future BMEII0861 research can be identified:

Molecular and Structural Studies:

• Structure-Function Analysis:

  • Determination of the three-dimensional structure of BMEII0861

  • Identification of critical residues for substrate binding and transport

  • Molecular docking studies to predict peptide-protein interactions (similar to approaches used for BME_RS12880)

• Substrate Specificity:

  • Identification of specific peptide substrates transported by BMEII0861

  • Investigation of potential role in antimicrobial peptide transport or resistance

  • Comparative analysis with other peptide transporters in Brucella

Functional Genomics Approaches:

• Transcriptomic Profiling:

  • RNA-Seq analysis under various infection-relevant conditions

  • Identification of co-regulated genes and regulatory networks

  • Comparison of expression patterns across different Brucella species and strains

• Comprehensive Mutational Analysis:

  • Generation of deletion mutants and point mutations

  • CRISPR-Cas9 based genome editing for precise modifications

  • Complementation studies with wild-type and mutant variants

• Protein-Protein Interaction Studies:

  • Identification of interaction partners within the ABC transporter complex

  • Investigation of potential interactions with host proteins

  • Construction of protein-protein interaction networks

Translational Research:

• Vaccine Development:

  • Evaluation of BMEII0861 alone and in combination with established immunogens

  • Optimization of expression systems for maximal immunogenicity

  • Assessment of protective efficacy in animal models

• Inhibitor Development:

  • High-throughput screening for inhibitors of BMEII0861 function

  • Structure-based drug design targeting the transport channel

  • Evaluation of inhibitors in cellular and animal infection models

• Diagnostic Applications:

  • Assessment of BMEII0861 as a biomarker for active infection

  • Development of serological assays based on recombinant BMEII0861

  • Exploration of point-of-care diagnostic applications

Systems Biology Integration:

• Multi-omics Approaches:

  • Integration of genomic, transcriptomic, and proteomic data

  • Metabolomic analysis to identify transported substrates

  • Construction of comprehensive systems biology models of Brucella infection

• Comparative Analysis Across Strains:

  • Examination of BMEII0861 conservation and variation across Brucella isolates

  • Correlation of sequence variations with virulence phenotypes

  • Application of findings to strain typing and epidemiological studies