Recombinant Francisella tularensis subsp. tularensis Ribosome-recycling factor (frr)

What is the ribosome-recycling factor (frr) in Francisella tularensis and what role does it play in bacterial physiology?

Methodological approach for characterization:

• Comparative genomics using sequence alignment tools to identify the frr gene in F. tularensis genome databases

• Structural prediction using cryo-electron microscopy to determine the 3D conformation of the protein

• Functional domain mapping through site-directed mutagenesis of conserved regions

• In vitro translation assays to quantify recycling activity using purified components

How does the frr protein in F. tularensis compare structurally and functionally to homologous proteins in other bacterial species?

The frr protein belongs to a highly conserved family of bacterial proteins involved in translation. While specific structural details of F. tularensis frr were not provided in the search results, research on bacterial ribosome recycling factors indicates they share common functional domains involved in ribosome binding and dissociation.

Methodological approach for comparative analysis:

• Multiple sequence alignment of frr proteins from F. tularensis subspecies (tularensis, holarctica, novicida) and related species like F. philomiragia

• Phylogenetic analysis using maximum likelihood methods to establish evolutionary relationships

• Structural comparison through homology modeling based on crystallized frr proteins from other bacteria

• Cross-complementation experiments to test functional conservation across species

What expression systems and purification protocols are most effective for producing recombinant F. tularensis frr?

Based on research with other F. tularensis proteins, several expression systems have been successfully employed to produce recombinant proteins from this organism.

Methodological approach for recombinant expression:

• E. coli expression systems using vectors containing appropriate affinity tags (His, GST, MBP)

• Optimization of induction conditions (IPTG concentration, temperature, induction time)

• Cell lysis under native conditions using either sonication or French press

• Purification through affinity chromatography followed by size exclusion chromatography

Sample purification protocol:

• Transform expression vector containing F. tularensis frr gene into E. coli BL21(DE3)

• Culture in LB medium to OD600 of 0.6-0.8 at 37°C

• Induce with 0.5mM IPTG at 18°C for 16-18 hours

• Harvest cells by centrifugation and resuspend in lysis buffer containing protease inhibitors

• Lyse cells and clarify lysate by centrifugation

• Purify using Ni-NTA affinity chromatography for His-tagged protein

• Further purify using ion exchange and size exclusion chromatography

What functional assays can verify the activity of recombinant F. tularensis frr?

Methodological approach for functional verification:

• Ribosome dissociation assay measuring the release of ribosomes from model post-termination complexes

• ATPase activity assay in the presence of elongation factor G

• Circular dichroism spectroscopy to confirm proper protein folding

• Thermal shift assays to assess protein stability

• Complementation studies in conditional frr mutants to verify in vivo functionality

How might the expression of frr in F. tularensis change during different stages of infection?

F. tularensis undergoes significant transcriptional and translational reprogramming during infection cycles. As it transitions from environmental survival to intracellular replication within host cells, the expression of essential genes like frr likely undergoes regulation.

Methodological approach for expression analysis:

• RNA-seq analysis of F. tularensis isolated from different infection stages

• Quantitative proteomics to measure frr protein levels during infection using LC-MS/MS proteome profiling

• Reporter gene fusions to monitor frr promoter activity in real-time during infection

• Single-cell analysis to assess heterogeneity in frr expression within bacterial populations

• Ribosome profiling to determine translational efficiency of frr mRNA during different growth phases

What role might frr play in F. tularensis pathogenesis and intracellular survival?

As a critical component of protein synthesis machinery, frr likely contributes to F. tularensis pathogenesis by enabling rapid adaptation to changing host environments through efficient protein production.

Methodological approach for studying pathogenesis:

• Construction of conditional frr mutants using inducible promoter systems

• Intracellular growth assays in macrophages and other relevant host cells

• Transcriptomic analysis comparing wild-type and frr-depleted strains during infection

• Proteomic analysis to identify proteins whose expression is most affected by frr depletion

• Animal infection models using optimized conditional mutants to assess virulence

How can we develop specific inhibitors targeting F. tularensis frr as potential therapeutics?

The essential nature of frr for bacterial survival makes it a potential target for novel antimicrobials. Developing inhibitors requires detailed understanding of both structure and function.

Methodological approach for inhibitor development:

• Structure-based virtual screening against the ribosome-binding interface of frr

• Fragment-based drug discovery identifying small molecules that bind to functional pockets

• High-throughput screening of compound libraries using in vitro translation assays

• Structure-activity relationship studies optimizing lead compounds

• Validation in cell culture and animal models of F. tularensis infection

How does environmental stress affect frr function in F. tularensis?

F. tularensis can persist in diverse environmental conditions, from soil to water sources, suggesting sophisticated stress response mechanisms . The function of translation machinery, including frr, may be modulated during environmental stress.

Methodological approach for stress studies:

• Exposure of F. tularensis to relevant environmental stressors (temperature, pH, nutrient limitation)

• qRT-PCR analysis of frr expression under different stress conditions

• Proteome analysis using LC-MS/MS to quantify frr levels during stress response

• In vitro translation assays under stress-mimicking conditions

• Analysis of frr protein modifications (phosphorylation, acetylation) during stress response

What experimental approaches can determine the interactome of F. tularensis frr?

Understanding the protein-protein interaction network of frr can provide insights into its regulatory mechanisms and potential moonlighting functions beyond ribosome recycling.

Methodological approach for interactome analysis:

• Pull-down assays using tagged recombinant frr as bait

• Crosslinking mass spectrometry to capture transient interactions

• Bacterial two-hybrid screening to identify protein partners

• Co-immunoprecipitation followed by LC-MS/MS identification of binding partners

• Proximity labeling techniques such as BioID to identify proteins in close proximity to frr in vivo

Comparative analysis of frr across Francisella species and subspecies

Optimization conditions for recombinant F. tularensis frr expression

Functional assays for verifying F. tularensis frr activity

Environmental factors affecting F. tularensis survival and potential impact on frr function

Genetic manipulation approaches for studying frr in F. tularensis

Given that frr is likely essential, conventional knockout approaches may not be viable. Instead, researchers should consider:

• Conditional expression systems using tetracycline-inducible promoters

• Partial depletion through antisense RNA expression

• Domain-specific mutations to affect function without eliminating viability

• Heterologous complementation with frr from other species to identify functional differences

• CRISPR interference (CRISPRi) for tunable gene repression

These approaches must be carefully optimized for F. tularensis, which requires specialized handling in BSL-3 facilities due to its classification as a Category A bioterrorism agent .

Contribution of frr to F. tularensis virulence mechanisms

F. tularensis employs multiple virulence mechanisms, including acid phosphatase production , type VI secretion systems , and immune evasion strategies. The role of frr in supporting these mechanisms could be investigated by:

• Measuring virulence factor production under frr depletion conditions

• Assessing intracellular survival in professional phagocytes with altered frr levels

• Quantifying escape from phagosomes when frr function is compromised

• Evaluating respiratory burst abrogation capacity with frr mutations

• Analyzing the impact of frr depletion on Francisella pathogenicity island protein expression

Integration of frr studies with environmental persistence investigations

The TULAMIBE project's focus on F. tularensis environmental survival could be extended to investigate how frr contributes to persistence in hydro-telluric environments. Key approaches include:

• Correlation of frr expression with survival in various soil compositions

• Assessment of translational efficiency in environmental versus host conditions

• Investigation of potential regulatory mechanisms linking environmental sensing to frr activity

• Development of biosensors using frr promoters to monitor F. tularensis activity in environmental samples

• Comparative analysis of frr function across Francisella species with different environmental niches

Applications of recombinant F. tularensis frr in diagnostic development

The development of rapid, culture-free identification methods for F. tularensis could be enhanced through applications of recombinant frr:

• Generation of specific antibodies against frr for immunodiagnostic applications

• Development of aptamer-based detection systems targeting frr

• Creation of activity-based probes to detect functional frr in environmental samples

• Integration of frr detection into multiplex PCR assays for comprehensive F. tularensis identification

• Exploration of frr sequence variations for subspecies-level discrimination in diagnostic applications