Recombinant Yersinia pseudotuberculosis serotype IB ATP synthase subunit b (atpF)

What experimental conditions are optimal for studying Y. pseudotuberculosis type III secretion system (T3SS) in relation to ATP-dependent processes?

T3SS expression and function in Y. pseudotuberculosis is highly regulated by environmental conditions that impact ATP utilization. For optimal T3SS expression, culture bacteria at 37°C in calcium-depleted media, which triggers secretion of Yop proteins. During experimental procedures, maintain these conditions for 5 hours to achieve maximum protein secretion . To differentiate between protein synthesis and secretion, compare protein presence in both cell lysates and culture supernatants using Western blotting. To assess if your protein of interest interacts with T3SS components, create mutations in key T3SS genes (yopB, yopD) that form the translocation pore and analyze effects on your target protein's expression or localization .

How do temperature and calcium concentration affect Y. pseudotuberculosis protein expression patterns?

Temperature and calcium availability serve as critical environmental signals that regulate Y. pseudotuberculosis virulence factor expression:

As evidenced in transcriptional studies, Y. pseudotuberculosis undergoes significant reprogramming between virulent (37°C) and persistent (26°C-like) modes . When designing experiments to study recombinant proteins, consider these expression patterns to interpret results in proper physiological context.

What genetic engineering strategies can be used to create recombinant Y. pseudotuberculosis strains for studying membrane proteins like ATP synthase components?

To create recombinant Y. pseudotuberculosis strains for membrane protein studies, implement a multi-step engineering approach:

• Design specific mutations in target genes using site-directed mutagenesis

• For attenuated vaccine strains, introduce multiple mutations like those demonstrated in strain χ10069 (ΔyopK ΔyopJ Δasd)

• Use balanced-lethal host-vector systems with essential gene complementation (e.g., asd gene with Asd+ plasmids) for stable maintenance of expression vectors without antibiotic selection

• For membrane proteins like ATP synthase components, include their native promoters and signal sequences to ensure proper localization

• Validate protein expression using immunoblotting under different growth conditions

• Confirm membrane localization using cellular fractionation techniques followed by Western blotting

This approach has been successfully used for the delivery of recombinant fusion proteins like YopE-LcrV in Y. pseudotuberculosis .

What methods are most effective for assessing the impact of Y. pseudotuberculosis effector proteins on host cell energy metabolism?

To investigate how Y. pseudotuberculosis effector proteins impact host cell energy metabolism:

• Implement proteomics approaches comparing wild-type infection versus infection with strains harboring catalytically inactive effectors (e.g., YopJC172A)

• Use pathway analysis software to identify differentially regulated metabolic networks—research has shown YopJ affects oxidative phosphorylation and mitochondrial function pathways

• Measure cellular ATP levels using luminescence-based assays

• Assess mitochondrial membrane potential using fluorescent probes

• Quantify oxygen consumption rate and extracellular acidification rate using Seahorse technology

• For specific effector proteins, create clean deletion mutants and catalytically inactive point mutants to distinguish between structural and enzymatic contributions

Proteomics studies have revealed that YopJ affects multiple metabolic pathways, including oxidative phosphorylation and mitochondrial dysfunction , suggesting effects on cellular energy production that may involve ATP synthase activity.

How does the SmpB-SsrA system influence the expression and activity of energy metabolism proteins in Y. pseudotuberculosis during infection?

The SmpB-SsrA system plays a critical role in Y. pseudotuberculosis pathogenesis by maintaining proper translational quality control. Research has demonstrated that mutations in smpB-ssrA genes render Y. pseudotuberculosis avirulent and unable to cause mortality in mice . This system's influence on energy metabolism proteins involves:

• Transcriptional regulation: The SmpB-SsrA system affects expression of numerous genes, including those involved in energy production

• Quality control of stalled ribosomes: This prevents accumulation of incomplete proteins that could interfere with energy metabolism complexes

• Stress adaptation: During host infection, this system helps maintain translational fidelity under stress conditions

To investigate relationships between SmpB-SsrA and specific proteins like ATP synthase components:

• Create smpB-ssrA mutants and compare expression levels of target proteins using qRT-PCR and Western blotting

• Perform RNA-seq analysis comparing wild-type and mutant strains during infection

• Use chromatin immunoprecipitation to identify potential regulatory interactions

• Assess ATP production capacity in wild-type versus mutant strains

Research has shown that smpB-ssrA mutants exhibit "severe deficiencies in expression and secretion of Yersinia virulence effector proteins" , suggesting broad impacts on protein expression that likely extend to energy metabolism components.

How does Y. pseudotuberculosis reprogram its energy metabolism during the transition from acute infection to persistence?

Y. pseudotuberculosis undergoes dramatic transcriptional reprogramming during the transition from acute infection to persistence. RNA-seq analysis of bacteria isolated from infected tissues revealed:

• Downregulation of T3SS virulence genes during persistent infection in the cecum

• Shift toward expression patterns resembling in vitro growth at 26°C during persistence

• Upregulation of genes associated with alternative energy utilization pathways

To study changes in specific components like ATP synthase during this transition:

• Perform temporal RNA-seq analysis focusing on energy metabolism genes

• Use reporter strains with fluorescent or luminescent proteins fused to promoters of interest

• Implement metabolomics approaches to track changes in cellular energy carriers

• Use selective inhibitors of energy metabolism to assess bacterial survival during different infection phases

This transcriptional reprogramming likely involves changes in energy metabolism to support long-term survival within host tissues. Interestingly, despite low bacterial numbers recovered from infected tissues (1×10^5 to 2×10^6 CFUs), relatively high amounts of bacterial RNA were detected, suggesting active transcription during persistence .

What roles do Y. pseudotuberculosis T3SS effectors play in modulating host immune responses, and how could this impact research on other bacterial components?

Y. pseudotuberculosis T3SS effectors actively modulate host immune responses through multiple mechanisms:

• YopJ inhibits MAPK/ERK signaling pathways that regulate inflammatory responses

• YopJ specifically downregulates prostaglandin E2 (PGE2) biosynthesis by inhibiting cyclooxygenase-2 (COX-2) expression

• T3SS pore formation triggers NFκB- and type I IFN-regulated gene expression independent of TLR signaling

• Caspase-1 activation by the T3SS is required for IL-1β secretion

When studying other bacterial components like ATP synthase, researchers must consider these immunomodulatory effects as they may indirectly impact results. For example, YopJ-mediated suppression of host metabolism could alter the environment in which membrane proteins function.

To isolate effects of specific bacterial components from these immunomodulatory activities, researchers should use defined mutants lacking specific effectors or the entire T3SS.

How can recombinant Y. pseudotuberculosis strains be engineered as vaccine delivery platforms for heterologous antigens?

Recombinant attenuated Y. pseudotuberculosis strains have demonstrated potential as vaccine vectors through strategic genetic modifications:

• Create attenuated background strains through multiple mutations affecting virulence (e.g., ΔyopK ΔyopJ Δasd)

• Implement balanced-lethal systems (e.g., Δasd mutation complemented with Asd+ plasmid) for stable antigen expression without antibiotic selection

• Express antigens as fusions with T3SS substrates (e.g., YopE amino acids 1-138) to facilitate delivery into host cells

• Optimize antigen expression through appropriate promoter selection and codon optimization

• Confirm immunogenicity through assessment of both mucosal and systemic immune responses

This approach has been demonstrated effective with the YopE-LcrV fusion protein, which provided 80% protection against Y. pestis challenge when delivered by an engineered Y. pseudotuberculosis strain . The protective efficacy suggests this platform could potentially be adapted for delivery of other bacterial antigens.

What emerging technologies could enhance studies of Y. pseudotuberculosis membrane proteins in different growth conditions?

Several cutting-edge technologies show promise for advancing studies of Y. pseudotuberculosis membrane proteins:

• Cryo-electron microscopy (cryo-EM) for high-resolution structural analysis of membrane protein complexes in near-native states

• Single-cell RNA-seq to characterize heterogeneity in bacterial populations during infection

• CRISPR interference (CRISPRi) for tunable gene repression to study essential membrane proteins

• Bio-orthogonal labeling approaches to track protein synthesis and turnover in vivo

• Advanced protein interaction techniques like proximity labeling to identify interaction partners

• Integrin-activating Invasin protein as a defined substrate for culturing epithelial cells in 2D format to study host-pathogen interactions

The recently discovered application of Invasin as an ECM-like ligand opens new possibilities for studying bacterial-host interactions in a controlled 2D environment that facilitates imaging, functional assays, and high-throughput screening .

How might ATP synthase components interact with virulence determinants in Y. pseudotuberculosis during different stages of pathogenesis?

While direct evidence for ATP synthase interactions with virulence factors is limited, several hypothetical mechanisms warrant investigation:

• Energy coupling between ATP synthase and protein secretion systems, particularly during times of high secretory demand

• Potential membrane domain co-localization between ATP synthase and the T3SS apparatus

• Metabolic regulation linking energy status to virulence gene expression

• Adaptation of energy production during different infection phases, particularly during the transition to persistence where Y. pseudotuberculosis undergoes significant transcriptional reprogramming

To investigate these potential relationships, researchers could:

• Perform co-immunoprecipitation experiments with tagged ATP synthase components

• Use super-resolution microscopy to visualize potential co-localization in the bacterial membrane

• Create conditional expression systems to modulate ATP synthase levels and assess impacts on virulence

• Implement metabolic flux analysis to track energy utilization during different infection phases

Understanding these interactions could reveal new therapeutic targets that disrupt the energetics of pathogenesis rather than targeting virulence factors directly.