Recombinant Listeria monocytogenes serovar 1/2a DNA translocase FtsK (ftsK)

How does recombinant L. monocytogenes FtsK differ from native protein in terms of structure and activity?

Recombinant L. monocytogenes FtsK is typically expressed with specific tags for purification and detection purposes. The recombinant protein maintains the core functional domains of native FtsK but may include:

• Affinity tags (determined during production process)

• Modified terminal regions

• Storage in optimized buffer conditions (Tris-based buffer with 50% glycerol)

These modifications generally preserve the primary structure and function while enabling laboratory manipulation. Activity comparisons between native and recombinant forms should be experimentally validated in each research context, with particular attention to:

• DNA binding affinity

• ATPase activity

• DNA translocation rates

• Interactions with other cell division proteins

What are the optimal storage and handling conditions for recombinant L. monocytogenes FtsK protein?

For optimal stability and activity, recombinant L. monocytogenes FtsK should be stored according to these guidelines:

The protein is typically supplied at a concentration suitable for most experimental applications (from 50 μg), and additional quantities may be available for larger-scale experiments .

What experimental approaches are most effective for studying FtsK activity in chromosome segregation?

To study FtsK activity in chromosome segregation, researchers should consider these methodological approaches:

• In vitro DNA translocation assays:

  • Using purified recombinant FtsK and fluorescently labeled DNA substrates

  • Measuring ATP-dependent DNA movement using single-molecule techniques

• Coevolution experiments:

  • Monitoring genetic variations that emerge under selective pressure

  • Analyzing both phage and bacterial host adaptations during reciprocal selection

• Comparative genomic analysis:

  • Contrasting FtsK functions across bacterial species (e.g., comparing with SpoIIIE in B. subtilis)

  • Identifying conserved domains and species-specific adaptations

• Live-cell imaging:

  • Tracking fluorescently tagged FtsK localization during cell division

  • Correlating FtsK positioning with chromosome segregation events

These approaches can be complementary, providing a comprehensive understanding of FtsK's role in chromosome dynamics.

How does L. monocytogenes FtsK contribute to bacterial pathogenesis and virulence?

L. monocytogenes FtsK's contribution to pathogenesis extends beyond its primary role in chromosome segregation:

• Cell division and persistence:

  • FtsK ensures faithful chromosome partitioning, maintaining bacterial fitness during infection

  • Proper chromosome segregation supports the persistent colonization of food processing facilities for years

• Potential interaction with virulence factors:

  • While direct evidence is limited, FtsK may influence expression or function of virulence factors

  • Cell division defects can trigger stress responses that modify virulence gene expression

• Role in biofilm formation:

  • Biofilms contribute to L. monocytogenes persistence in food processing environments

  • FtsK-mediated chromosome segregation ensures genomic integrity during biofilm development

• Response to environmental stressors:

  • FtsK function may be modulated during exposure to food preservation methods

  • Adaptations in FtsK could contribute to survival under antimicrobial treatments

These pathogenesis-related functions make FtsK and its recombinant versions important targets for food safety and infection control research.

What is the role of FtsK in phage resistance and coevolution dynamics?

FtsK plays a complex role in phage-host interactions and coevolution dynamics:

• DNA metabolism during phage infection:

  • FtsK-mediated DNA translocation may influence phage DNA packaging or replication

  • Mutations in FtsK could alter susceptibility to phage infection

• Coevolution experiments reveal:

  • L. monocytogenes develops phage resistance through various genetic mechanisms

  • Phages adapt to overcome resistance through mutations and recombination events

  • These dynamics can inform development of more effective phage-based biocontrol strategies

• Evolutionary implications:

  • Phage pressure may drive FtsK sequence diversity across L. monocytogenes strains

  • FtsK variants could influence horizontal gene transfer rates, affecting bacterial evolution

Research shows that in vitro evolution of phages can expand host range and improve long-term efficacy of phage-based control of L. monocytogenes, with potential applications in biocontrol, detection, and phage therapy .

How does L. monocytogenes FtsK compare to homologous proteins in other bacterial species?

L. monocytogenes FtsK belongs to a conserved family of bacterial translocases with homologs across diverse bacterial species. Key comparative insights include:

Unlike E. coli, which has one FtsK protein, B. subtilis contains two distinct FtsK/SpoIIIE-like proteins with specialized functions. SftA plays a role similar to E. coli FtsK during each cell cycle, while SpoIIIE functions in post-septational DNA translocation, especially during sporulation .

The presence of two FtsK/SpoIIIE paralogs is not conserved among all endospore-forming bacteria but is highly conserved within several groups of soil- and plant-associated bacteria .

What evolutionary insights can be gained from studying the genetic diversity of FtsK across L. monocytogenes strains?

Studying FtsK diversity across L. monocytogenes strains reveals important evolutionary insights:

This evolutionary perspective provides context for understanding strain-specific variations in pathogenicity and environmental persistence.

How can recombinant L. monocytogenes FtsK be utilized in vaccine development?

Recombinant L. monocytogenes FtsK offers several potential applications in vaccine development:

• Vector for antigen delivery:

  • L. monocytogenes serves as an effective vaccine vector due to its ability to stimulate robust cellular immune responses

  • Recombinant L. monocytogenes can be engineered to secrete bacterial antigens and tumor antigens

• PEST sequence utilization:

  • PEST sequences (found in proteins with short cellular half-life) can be incorporated into recombinant L. monocytogenes vaccines

  • These sequences target proteins for degradation in the ubiquitin-proteasome pathway, enhancing immunogenicity

• Enhanced antigen processing:

  • FtsK or its domains might be fused to target antigens to improve processing and presentation

  • This approach could potentially enhance CD8+ T cell responses against target antigens

• Experimental findings:

  • Studies show that Listeria expressing fusion proteins containing PEST sequences effectively regress established tumors in mouse models

  • Strong correlation exists between CD8+ T cell induction, tumor homing, and antitumor efficacy of the Listeria-based vaccines

These applications highlight the potential of recombinant L. monocytogenes FtsK in both infectious disease and cancer immunotherapy development.

What are the challenges and solutions in producing high-quality recombinant L. monocytogenes FtsK for research applications?

Production of high-quality recombinant L. monocytogenes FtsK presents several challenges that researchers must address:

Quality control measures should include:

• Verification of protein purity by SDS-PAGE and Western blotting

• Assessment of DNA-binding activity through electrophoretic mobility shift assays

• Evaluation of ATPase activity using colorimetric phosphate release assays

• Testing for endotoxin contamination, especially for immunological applications

When stored properly in Tris-based buffer with 50% glycerol at -20°C or -80°C, high-quality recombinant protein can maintain activity for extended periods .

What are common pitfalls in FtsK functional assays and how can they be addressed?

When conducting functional assays with recombinant L. monocytogenes FtsK, researchers frequently encounter these challenges:

• ATP hydrolysis background levels:

  • Issue: High background ATPase activity in preparations

  • Solution: Include appropriate controls without DNA substrates; purify protein to >95% homogeneity

• DNA substrate specificity:

  • Issue: Inconsistent translocation activity with different DNA templates

  • Solution: Use defined DNA substrates with characterized FtsK recognition sequences; test multiple template designs

• Buffer optimization:

  • Issue: Suboptimal activity due to buffer conditions

  • Solution: Systematically test different buffer compositions, including variations in:

    • Divalent cation concentrations (Mg²⁺, Ca²⁺)

    • pH range (6.5-8.5)

    • Salt concentrations (50-200 mM)

• Protein aggregation during assays:

  • Issue: Loss of activity due to protein aggregation

  • Solution: Include stabilizing agents (glycerol, BSA); avoid freeze-thaw cycles; centrifuge samples before use

• Assay detection limits:

  • Issue: Insufficient sensitivity to detect translocation events

  • Solution: Employ fluorescence-based assays or single-molecule techniques with higher sensitivity

Each of these challenges can be addressed through careful experimental design and appropriate controls.

How can researchers design experiments to study FtsK's role in L. monocytogenes pathogenesis?

To effectively study FtsK's role in L. monocytogenes pathogenesis, researchers should consider these experimental approaches:

• Genetic manipulation strategies:

  • Generate conditional mutants (as complete knockouts may be lethal)

  • Create domain-specific mutations that separate chromosome segregation from other functions

  • Employ CRISPR-Cas9 for precise genetic modifications

• Infection models:

  • Cell culture: Human intestinal epithelial cells for invasion assays

  • Animal models: Guinea pig or mouse models of listeriosis

  • Evaluation parameters: Bacterial burden, dissemination, immune response

• Expression analysis:

  • Measure FtsK expression levels during different infection stages

  • Compare expression in virulent vs. attenuated strains

  • Analyze regulation under infection-relevant stresses

• Coevolution experiments:

  • Setup: L. monocytogenes cultures with phages at multiplicity of infection (MOI) of 1

  • Monitoring: OD₆₀₀ measurements for 55-60 hours

  • Sampling: Isolate bacterial survivors at 6-8 hours post-infection and during early regrowth (OD₆₀₀ 0.05-0.1)

  • Analysis: Whole-genome sequencing to identify mutations and adaptations

• Protein-protein interaction studies:

  • Identify FtsK interaction partners during infection

  • Assess how these interactions change in different host environments

These approaches can be integrated to provide a comprehensive understanding of FtsK's multifaceted roles in L. monocytogenes pathogenesis.

What emerging technologies could advance our understanding of L. monocytogenes FtsK?

Several cutting-edge technologies show promise for deepening our understanding of L. monocytogenes FtsK:

• Cryo-electron microscopy (Cryo-EM):

  • High-resolution structural analysis of FtsK complexes with DNA

  • Visualization of conformational changes during ATP hydrolysis and translocation

• Single-cell sequencing applications:

  • Analysis of FtsK expression heterogeneity within bacterial populations

  • Correlation with cell cycle stages and virulence factor expression

• Microfluidics combined with live-cell imaging:

  • Real-time visualization of FtsK dynamics during cell division

  • Measurement of chromosome segregation kinetics under controlled conditions

• CRISPR interference (CRISPRi):

  • Tunable repression of FtsK expression to study dosage effects

  • Temporal control of FtsK availability during infection

• Synthetic biology approaches:

  • Creation of minimal functional FtsK variants

  • Engineering orthogonal systems to dissect individual FtsK functions

These technologies could resolve longstanding questions about FtsK mechanism and function in L. monocytogenes biology and pathogenesis.

What are the potential implications of FtsK research for developing novel antimicrobial strategies?

Research on L. monocytogenes FtsK has several promising implications for antimicrobial development:

• FtsK as a direct drug target:

  • Essential nature makes it an attractive antibacterial target

  • ATP-binding pocket offers potential binding sites for small molecule inhibitors

  • Species-specific domains could enable selective targeting

• Phage-based biocontrol strategies:

  • Understanding FtsK's role in phage resistance can inform improved phage cocktails

  • In vitro evolution of phages can overcome bacterial resistance mechanisms

  • Engineered phages targeting FtsK-dependent processes could enhance killing efficiency

• Vaccine development applications:

  • Recombinant L. monocytogenes vectors expressing immunogenic epitopes

  • PEST sequence incorporation to enhance antigen processing and presentation

  • Multi-antigen constructs targeting both bacterial and tumor antigens

• Diagnostic applications:

  • FtsK-specific detection methods for environmental or clinical samples

  • Strain-specific core genome MLST schemes including FtsK for outbreak tracking

These applications highlight how fundamental research on L. monocytogenes FtsK can translate into practical tools for addressing food safety concerns and treating listeriosis infections.