Recombinant Yersinia pseudotuberculosis serotype IB Bifunctional protein aas (aas)

What is the bifunctional protein aas in Yersinia pseudotuberculosis and what are its primary functions?

The bifunctional protein aas in Y. pseudotuberculosis is a membrane-associated protein with dual enzymatic activities. It functions in bacterial membrane homeostasis and phospholipid metabolism, playing roles in both membrane biogenesis and remodeling. The protein demonstrates 2-acylglycerophosphoethanolamine acyltransferase and acyl-acyl carrier protein synthetase activities, enabling it to participate in phospholipid recycling pathways that are critical for bacterial membrane integrity and adaptation to environmental stresses .

Research methods to characterize these functions include:

• Site-directed mutagenesis to identify catalytic residues

• Radiolabeled substrate assays to measure enzymatic activity

• Membrane fraction isolation and activity reconstitution

• Complementation studies in bacterial knockout strains

How does the structure of the aas protein relate to its bifunctional properties?

The aas protein contains distinct domains that confer its bifunctional properties:

• An N-terminal domain with multiple transmembrane segments anchoring the protein to the bacterial membrane

• A central acyltransferase domain responsible for lipid remodeling

• A C-terminal acyl-ACP synthetase domain that activates fatty acids

These domains work cooperatively but maintain structural independence, allowing the protein to coordinate membrane lipid metabolism through dual catalytic activities. Structural analysis approaches include X-ray crystallography of soluble domains, cryo-EM for membrane-embedded regions, and molecular dynamics simulations to understand interdomain interactions .

What are the optimal expression systems for producing recombinant Y. pseudotuberculosis aas protein?

The optimal expression systems for producing recombinant Y. pseudotuberculosis aas protein depend on research objectives:

For membrane proteins like aas, specialized E. coli strains (C41, C43) may provide better expression outcomes by managing toxicity. Codon optimization for the expression host and incorporation of Ala or Ser at the +2 position after the initiation codon can increase expression yields by up to 10-fold .

What strategies can optimize the solubility and yield of recombinant aas protein?

To optimize solubility and yield of this challenging membrane-associated protein:

• Fusion tags selection:

  • N-terminal solubility tags (MBP, SUMO, TrxA) to improve folding

  • C-terminal affinity tags (His6) for purification

  • Careful consideration of tag removal strategies

• Expression conditions optimization:

  • Lower temperature cultivation (16-20°C) to slow folding

  • Reduced inducer concentration to prevent aggregation

  • Addition of membrane-mimicking detergents during cell lysis

• Protein engineering approaches:

  • Domain-based expression for difficult regions

  • Deletion of transmembrane regions for soluble domain studies

  • Surface entropy reduction mutagenesis

• Media formulation:

  • Auto-induction media for controlled expression

  • Supplementation with phospholipids or membrane components

Implementing a high-throughput process development (HTPD) strategy allows for parallel screening of multiple parameters to rapidly identify optimal conditions .

How can researchers distinguish between the dual catalytic activities of the aas protein in experimental settings?

Distinguishing between the dual catalytic activities requires specialized biochemical approaches:

• Domain-specific mutants:

  • Generate point mutations in catalytic residues of each domain

  • Express and purify variants with single active domains

  • Compare activities of wild-type vs. mutant proteins

• Substrate specificity analysis:

  • Acyltransferase activity: monitored using fluorescent phospholipid analogs

  • Acyl-ACP synthetase activity: measured through ATP consumption or radiolabeled fatty acid incorporation

• Sequential reaction blocking:

  • Utilize domain-specific inhibitors

  • Employ competing substrates to selectively impede one activity

  • Design reaction conditions favoring single activity assessment

• Coupled enzyme assays:

  • Develop spectrophotometric assays linking activity to measurable outputs

  • Employ biosensors for real-time activity monitoring

These methods allow for quantitative assessment of each function independently, enabling structure-function correlation studies .

What are the advanced approaches for studying membrane association of the aas protein?

Advanced approaches for studying membrane association include:

• Nanodiscs and liposome reconstitution:

  • Incorporation of purified protein into synthetic lipid bilayers

  • Assessment of activity in membrane-mimetic environments

  • Evaluation of lipid preferences for optimal function

• Fluorescence microscopy techniques:

  • FRET analysis of protein-lipid interactions

  • Single-molecule tracking in model membranes

  • Super-resolution imaging of membrane localization

• Neutron reflectometry and scattering:

  • Determination of protein orientation in membranes

  • Measurement of penetration depth into lipid bilayers

  • Analysis of protein-induced membrane perturbations

• Atomic force microscopy:

  • Topographical mapping of protein in membranes

  • Force spectroscopy to measure membrane-protein interactions

  • Time-lapse imaging of functional dynamics

These techniques provide complementary data that collectively reveal how the protein interfaces with bacterial membranes in its native environment .

How does the aas protein contribute to Y. pseudotuberculosis pathogenesis and survival in host environments?

The aas protein contributes to Y. pseudotuberculosis pathogenesis through multiple mechanisms:

• Membrane adaptation during infection:

  • Modifies phospholipid composition in response to host environments

  • Facilitates resistance to host-derived antimicrobial peptides

  • Contributes to membrane integrity under stress conditions

• Metabolic adaptation:

  • Enables recycling of fatty acids from damaged membranes

  • Conserves energy during nutrient limitation in host tissues

  • Supports membrane remodeling during temperature transitions

• Virulence factor regulation:

  • Indirectly affects membrane-associated virulence factors

  • May influence type III secretion system function through membrane composition

  • Potentially interacts with the virulence plasmid pYV components

Research methodologies to establish these connections include infection models with aas-deficient mutants, transcriptomic profiling during host cell interaction, and membrane composition analysis during various infection stages .

What methodological approaches can link aas protein function to bacterial survival in immunocompromised hosts?

Given the reported cases of Y. pseudotuberculosis septicemia in immunocompromised patients, particularly those with HIV infection , several methodological approaches can investigate the relationship between aas function and bacterial survival:

• In vitro immune cell interaction studies:

  • Bacterial survival assays in primary human macrophages

  • Comparison of wild-type vs. aas mutant phagocytosis resistance

  • Assessment of membrane integrity under oxidative stress conditions

• Ex vivo tissue modeling:

  • Organoid cultures mimicking intestinal or lymphatic tissues

  • Bacterial transcriptomics to analyze aas expression in tissue environments

  • Competitive infection experiments with tagged bacterial strains

• Animal models of immunodeficiency:

  • Humanized mouse models with controlled immune deficits

  • Sequential sampling to track membrane adaptation during infection

  • Histopathological analysis of tissue tropism correlating with aas expression

• Clinical isolate comparative genomics:

  • Analysis of aas sequence variations among clinical isolates

  • Correlation of expression levels with clinical outcomes

  • Functional genomics to identify compensatory pathways

These approaches help establish whether aas contributes to the particular virulence of Y. pseudotuberculosis in immunocompromised hosts, potentially identifying new therapeutic targets .

How can synthetic biology approaches be used to modify the bifunctional properties of the aas protein for research applications?

Synthetic biology offers powerful tools to engineer the bifunctional properties of aas:

• Domain shuffling and protein chimeras:

  • Creation of hybrid proteins with combined functionalities

  • Fusion of aas domains with reporter proteins for activity monitoring

  • Development of orthogonal bifunctional systems for metabolic engineering

• Activity tuning through directed evolution:

  • Error-prone PCR to generate variant libraries

  • Activity-based screening methods to identify improved variants

  • Compartmentalized self-replication techniques for membrane protein evolution

• Computational design approaches:

  • In silico modeling of substrate binding sites

  • Rational design of altered substrate specificity

  • Prediction of allosteric regulation mechanisms

• Optogenetic and chemogenetic control:

  • Integration of light-sensitive domains for activity modulation

  • Development of chemically-inducible dimerization systems

  • Creation of conditionally active protein variants

These engineering approaches enable the development of research tools for studying membrane biology and potentially therapeutic applications targeting bacterial membrane homeostasis .

What considerations are important when designing experiments to study the interaction between aas and other virulence factors?

When designing experiments to study interactions between aas and other virulence factors, researchers should consider:

• Temporal expression dynamics:

  • Coordinate measurement of aas and virulence factor expression

  • Time-course analyses during infection progression

  • Inducible expression systems for controlled protein production

• Spatial localization in bacteria:

  • Membrane microdomain analysis through super-resolution microscopy

  • Co-localization studies with fluorescently tagged proteins

  • Biochemical fractionation to identify protein-protein interactions

• Functional dependencies:

  • Construction of conditional expression strains

  • Epistasis analysis through double mutant characterization

  • Protein-protein interaction mapping using bacterial two-hybrid systems

• Environmental context:

  • Simulation of host microenvironments (pH, temperature, nutrients)

  • Host cell co-culture systems for relevant biological context

  • In vivo imaging of bacterial protein dynamics during infection

• Data integration approaches:

  • Multi-omics integration (proteomics, lipidomics, transcriptomics)

  • Network analysis of virulence factor dependencies

  • Mathematical modeling of membrane dynamics and virulence

These experimental considerations help establish causal relationships between membrane homeostasis and virulence mechanisms, particularly in the context of the virulence plasmid pYV and its encoded type III secretion system .

What are the major challenges in purifying active recombinant aas protein and how can they be overcome?

Purifying active recombinant aas protein presents several challenges due to its membrane association:

Implementation of high-throughput screening approaches allows systematic testing of conditions that preserve both acyltransferase and acyl-ACP synthetase activities after purification. For structural studies, limited proteolysis followed by mass spectrometry can identify stable domains suitable for crystallization .

How can researchers develop reliable functional assays for both activities of the aas protein?

Developing reliable functional assays for both activities requires careful consideration of reaction conditions:

• Acyltransferase activity assays:

  • Radioactive assays: [14C]-labeled lysophospholipid substrate incorporation

  • Fluorescence-based: FRET-labeled phospholipid analogs

  • Coupled enzyme systems: linking acyl transfer to NAD(P)H consumption

  • High-throughput: Colorimetric detection of released products

• Acyl-ACP synthetase activity assays:

  • ATP consumption measurement via luciferase-coupled assay

  • AMP formation detection through coupled enzyme systems

  • Direct monitoring of acylated ACP by gel shift or mass spectrometry

  • Isothermal titration calorimetry for binding energetics

• Assay validation approaches:

  • Use of specific inhibitors to confirm activity specificity

  • Controls with catalytically inactive mutants

  • Correlation of activity with protein concentration

  • Assessment of kinetic parameters (Km, Vmax, kcat)

• Scaling considerations:

  • Miniaturization for 96/384-well format compatibility

  • Automation of reaction setup and measurement

  • Development of continuous rather than endpoint assays

  • Statistical validation for reproducibility

These assays enable quantitative assessment of structure-function relationships and provide tools for inhibitor screening that may lead to new antimicrobial strategies .

How can understanding the aas protein advance our knowledge of Y. pseudotuberculosis infection in immunocompromised patients?

Understanding the aas protein can significantly advance knowledge of Y. pseudotuberculosis pathogenesis in immunocompromised patients through several research avenues:

• Membrane adaptation mechanisms:

  • Analysis of membrane composition changes in bacterial isolates from immunocompromised patients

  • Correlation between aas activity levels and bacterial persistence

  • Investigation of membrane remodeling as a stress response to host immunity

• Host-pathogen interface studies:

  • Examination of aas-dependent resistance to host antimicrobial peptides

  • Analysis of membrane modifications that evade immune recognition

  • Investigation of phospholipid metabolism as a virulence determinant

• Therapeutic targeting approaches:

  • Identification of aas inhibitors that synergize with compromised immunity

  • Development of membrane-targeted therapeutics specific to pathogenic Yersinia

  • Design of combination therapies addressing membrane homeostasis disruption

• Diagnostic applications:

  • Monitoring of aas expression as a marker of active infection

  • Development of molecular diagnostics targeting aas sequence variants

  • Correlation of aas activity with clinical outcomes

Given the documented cases of Y. pseudotuberculosis septicemia in HIV-positive patients , research into aas function may reveal specific adaptations that enable bacterial survival in immunocompromised hosts and provide new therapeutic approaches for these vulnerable populations.

What methodological approaches can determine if aas protein interacts with the virulence plasmid pYV components?

To investigate potential interactions between the aas protein and pYV virulence plasmid components, researchers can employ these methodological approaches:

• Protein-protein interaction detection:

  • Bacterial two-hybrid screening against pYV-encoded proteins

  • Co-immunoprecipitation with tagged aas protein

  • Cross-linking mass spectrometry to capture transient interactions

  • Surface plasmon resonance for direct binding assessment

• Functional genomics approaches:

  • Transcriptomic analysis of pYV gene expression in aas mutants

  • Suppressor mutation screening to identify genetic interactions

  • Synthetic lethality analysis between aas and pYV components

  • CRISPRi knockdown of aas during activation of virulence mechanisms

• Spatial organization studies:

  • Fluorescence microscopy to track co-localization of aas with T3SS components

  • Super-resolution imaging of membrane domains during virulence activation

  • Biochemical fractionation to identify membrane microdomains containing both elements

  • Electron microscopy to visualize membrane architecture at injection sites

• Functional outcome measurements:

  • Type III secretion efficiency in aas mutants vs. wild-type

  • Impact of altered membrane composition on effector translocation

  • Assessment of Yop delivery into host cells with manipulated aas expression

These methodologies can determine whether aas-mediated membrane homeostasis directly or indirectly affects the function of the T3SS and other virulence mechanisms encoded by the pYV plasmid .

How do aas proteins from different Yersinia species compare functionally and structurally?

Comparative analysis of aas proteins across Yersinia species reveals evolutionary insights:

Research methodologies for comparative analysis include:

• Heterologous expression and functional complementation

• Domain swapping between species variants

• Phylogenetic analysis correlated with functional characterization

• Structural homology modeling and molecular dynamics simulations

These comparative approaches can reveal how aas adaptation has contributed to the divergent evolution of pathogenic Yersinia species from common ancestors .

What experimental design would best determine if aas protein function correlates with serotype-specific virulence?

To establish correlation between aas function and serotype-specific virulence, a comprehensive experimental design would include:

• Systematic strain collection and categorization:

  • Obtain clinical isolates representing all major serotypes

  • Document virulence phenotypes in standardized infection models

  • Sequence aas genes to identify serotype-specific variations

• Structure-function analysis across serotypes:

  • Express and purify aas proteins from different serotypes

  • Compare biochemical activities using standardized assays

  • Analyze membrane lipid profiles associated with each serotype

• Genetic complementation experiments:

  • Generate aas knockout strains in multiple serotype backgrounds

  • Cross-complement with aas variants from different serotypes

  • Assess restoration of virulence phenotypes

• Host-interaction phenotyping:

  • Compare serotype-specific membrane properties during host cell contact

  • Analyze aas expression during infection across serotypes

  • Measure immune evasion capabilities correlated with aas variants

• Statistical analysis and modeling:

  • Multivariate analysis to correlate aas sequence/activity with virulence metrics

  • Machine learning approaches to identify predictive features

  • Population genetics analysis of aas evolution within serotypes

This research design would enable statistical determination of whether serotype IB-specific features of the aas protein contribute to distinctive virulence characteristics compared to other Y. pseudotuberculosis serotypes .