Recombinant Yersinia pseudotuberculosis serotype O:3 UPF0761 membrane protein YPK_4186 (YPK_4186)

How does Yersinia pseudotuberculosis relate to other Yersinia species evolutionarily?

Yersinia pseudotuberculosis belongs to the Yersinia genus within the Enterobacteriaceae family. Population genetics studies have revealed that Yersinia pestis evolved from Y. pseudotuberculosis relatively recently, approximately 1,500–20,000 years ago . This represents one of the most rapid documented cases of a new human pathogen emerging from a less virulent ancestor .

Despite their close genetic relationship, Y. pseudotuberculosis and Y. pestis display markedly different ecology, epidemiology, and pathogenicity. Y. pseudotuberculosis functions primarily as a mammalian enteropathogen found widely in the environment, while Y. pestis has evolved into a blood-borne pathogen capable of parasitizing insects and causing systemic disease .

Both Y. pseudotuberculosis and Y. pestis, along with Y. enterocolitica, target lymph tissues during infection and carry a 70-kb virulence plasmid (pYV) that is essential for infection in these tissues and for overcoming host defense mechanisms .

What databases and resources are available for researching YPK_4186?

Researchers investigating YPK_4186 can access information from multiple databases:

• UniProtKB/Swiss-Prot: Contains the reviewed entry (B1JR04) with annotation and sequence data

• EMBL/GenBank/DDBJ: Contains the nucleotide sequence under accession CP000950

• RefSeq: Contains the protein sequence under accession WP_012304781.1

• AlphaFoldDB: Provides structural predictions under identifier B1JR04

• EnsemblBacteria: Contains annotation under identifier ACA70445

• KEGG: Maps the protein in metabolic and signaling pathways under ypy:YPK_4186

• PATRIC: Bacterial bioinformatics database with the entry fig|502800.11.peg.537

• GO (Gene Ontology): Contains functional annotation GO:0005887 (integral component of plasma membrane)

• Protein domain databases: InterPro (IPR023679, IPR017039), PANTHER (PTHR30213), and Pfam (PF03631)

What experimental approaches are recommended for expressing recombinant YPK_4186?

When expressing recombinant YPK_4186, researchers should consider the challenges associated with membrane protein expression:

For specific purification of YPK_4186, researchers can reference established protocols for membrane proteins while customizing the approach based on the unique characteristics of this protein.

How might the UPF0761 membrane protein YPK_4186 contribute to Yersinia pseudotuberculosis virulence?

While direct evidence of YPK_4186's role in virulence is not fully established in the provided search results, several insights can guide hypothesis development:

• Membrane protein function: As a multi-pass membrane protein, YPK_4186 may play a role in nutrient acquisition, signal transduction, or interaction with host cells during infection . The protein contains the Virul_fac_BrkB domain (Pfam: PF03631), which is associated with virulence factors in some bacteria .

• Related virulence mechanisms: Other Yersinia species contain insecticidal toxin complex (TC) genes that contribute to virulence. For example, in Y. enterocolitica biotype 1A, genes such as tcbA, tcaC, and tccC are homologous to insecticidal TC genes and contribute to virulence by facilitating persistence in vivo . Investigating whether YPK_4186 interacts with or modulates the activity of these toxin complexes could be valuable.

• Experimental approach: To investigate YPK_4186's potential role in virulence:

  • Generate YPK_4186 knockout mutants and assess their ability to colonize the gastrointestinal tract in mouse models

  • Perform comparative proteomics between wild-type and knockout strains

  • Assess protein-protein interactions between YPK_4186 and known virulence factors

  • Evaluate differential gene expression in response to host-like conditions

• Regulatory networks: Examine whether YPK_4186 expression changes in response to environmental conditions mimicking the host environment, which would suggest a potential role in adaptation during infection.

What challenges should researchers anticipate when working with YPK_4186 and how can they be addressed?

Researchers working with YPK_4186 should anticipate several technical challenges:

• Membrane protein solubility: As a multi-pass membrane protein, YPK_4186 is highly hydrophobic and may aggregate during expression and purification .

  • Solution: Use appropriate detergents or nanodiscs to maintain solubility; consider fusion partners that enhance solubility such as MBP (maltose-binding protein) or SUMO.

• Expression yield: Membrane proteins often express at lower levels than soluble proteins .

  • Solution: Optimize expression conditions including temperature, induction time, and inducer concentration; consider using specialized expression strains like C41(DE3) or C43(DE3) for toxic membrane proteins.

• Protein truncation: Translation initiation problems may lead to truncated products .

  • Solution: Use dual fusion tags to identify and purify only full-length protein; increase imidazole concentration during elution to separate full-length from truncated versions.

• Functional assays: Determining the functionality of recombinant YPK_4186 may be challenging without knowing its natural substrate or activity.

  • Solution: Develop binding assays with potential ligands; study the protein in reconstituted membrane systems; perform comparative analyses with known UPF0761 family members.

• Structural analysis: Membrane proteins are notoriously difficult to crystallize for structural studies .

  • Solution: Consider alternative structural approaches like cryo-EM or NMR for smaller domains; use computational modeling based on similar proteins; leverage AlphaFold2 predictions as starting points.

How can researchers assess the subcellular localization and topology of YPK_4186?

Confirming the predicted subcellular localization and determining the membrane topology of YPK_4186 requires multiple complementary approaches:

• Fluorescent protein fusions: Create N-terminal and C-terminal GFP fusions to visualize localization in live cells. Compare these results with the predicted cell inner membrane localization .

• Membrane fractionation: Perform subcellular fractionation to separate inner and outer membranes, followed by Western blotting to detect the protein in specific fractions.

• Protease accessibility assays: To determine topology (which regions face the cytoplasm versus periplasm):

  • Create spheroplasts and treat with proteases like trypsin or proteinase K

  • Analyze protected fragments by mass spectrometry

  • Compare results with computational predictions of transmembrane domains

• Cysteine substitution and labeling: Introduce cysteine residues at various positions and assess their accessibility to membrane-impermeable sulfhydryl reagents to map topology.

• Immunogold electron microscopy: Use antibodies against YPK_4186 with gold-conjugated secondary antibodies to visualize localization at high resolution.

• Computational validation: Cross-reference experimental results with predictions from TMHMM, TOPCONS, or other membrane protein topology prediction tools.

This multi-faceted approach will provide robust evidence of both localization and topology, which is crucial for understanding the protein's function in its native context.

What can amino acid sequence analysis reveal about YPK_4186's potential function?

Detailed sequence analysis of YPK_4186 can provide significant insights into its potential function:

• Domain architecture: The protein contains the Virul_fac_BrkB domain (IPR017039) , which has been associated with virulence factors in other bacteria. This suggests potential involvement in pathogenicity or host interaction.

• P2 amino acid analysis: Examining the second amino acid position (P2) can provide insights into protein processing and stability. The table below shows P2 residue frequencies in cytosolic proteins:

YPK_4186 contains alanine at position 2 (see sequence: MASFRFRLLSPLKP...) , which falls into the Ubr-QC-incompatible category according to the P2 amino acid usage data . This suggests the protein may have specific degradation patterns or stability characteristics.

• Transmembrane prediction: Hydrophobicity analysis of the sequence reveals multiple potential transmembrane helices, consistent with its annotation as a multi-pass membrane protein .

• Conservation analysis: Comparison with other UPF0761 family members can identify conserved residues that might be functionally important. This approach can highlight potential active sites or binding interfaces.

• Structural homology: While YPK_4186 is classified as an "uncharacterized protein family" (UPF), structural predictions from AlphaFold2 might reveal structural similarities to proteins of known function, providing functional hypotheses.

What are the recommended protocols for validating antibodies against YPK_4186?

Thorough antibody validation is critical for studies involving YPK_4186. A comprehensive validation approach should include:

• Western blot analysis:

  • Test antibody against recombinant YPK_4186 protein

  • Compare wild-type Y. pseudotuberculosis with YPK_4186 knockout strains

  • Include positive and negative controls (other Yersinia species)

  • Perform peptide competition assays to confirm specificity

• Immunoprecipitation:

  • Perform IP from membrane fractions of Y. pseudotuberculosis

  • Confirm pulled-down protein identity by mass spectrometry

  • Test reciprocal IP if antibodies to interaction partners are available

• Immunofluorescence microscopy:

  • Compare localization patterns with computational predictions

  • Include membrane markers to confirm inner membrane localization

  • Use YPK_4186 knockout strains as negative controls

• Testing across conditions:

  • Evaluate antibody performance under different fixation methods

  • Test antibody recognition under native and denatured conditions

  • Assess cross-reactivity with homologous proteins from related Yersinia species

• Quantitative validation:

  • Determine antibody affinity and specificity parameters

  • Establish optimal working concentrations for different applications

  • Document batch-to-batch variation if using polyclonal antibodies

This systematic approach ensures reliable antibody-based detection of YPK_4186 for various experimental applications.

How can researchers design functional assays for YPK_4186 given its unknown function?

Designing functional assays for a protein of unknown function requires a systematic approach:

• Comparative genomics-based approach:

  • Identify organisms where YPK_4186 homologs are present vs. absent

  • Compare phenotypic differences between these organisms to generate functional hypotheses

  • Investigate genetic context: are nearby genes functionally related?

• Gene knockout studies:

  • Generate YPK_4186 knockout strains using CRISPR-Cas9 or traditional homologous recombination

  • Perform phenotypic screens under various conditions (different nutrients, stressors, host cells)

  • Compare growth rates, membrane integrity, and virulence phenotypes between wild-type and knockout strains

• Protein-protein interaction studies:

  • Perform pull-down assays using tagged YPK_4186 as bait

  • Use proximity labeling methods like BioID or APEX to identify neighboring proteins

  • Validate interaction partners with co-immunoprecipitation and FRET/BRET assays

• Membrane transport assays (given its membrane localization):

  • Reconstitute purified YPK_4186 in liposomes with fluorescent indicators

  • Test for transport of various substrates (ions, small molecules)

  • Measure membrane potential changes in response to different conditions

• Expression profiling:

  • Analyze conditions where YPK_4186 is upregulated or downregulated

  • Use RNA-seq to identify genes co-regulated with YPK_4186

  • Test phenotypes under these specific conditions

This multi-faceted approach increases the likelihood of identifying functional roles of YPK_4186 despite the initial lack of functional annotation.

What comparative genomics approaches would be most informative for studying YPK_4186?

Comparative genomics offers powerful insights for studying proteins of unknown function like YPK_4186:

• Ortholog identification and conservation analysis:

  • Use tools like OrthoMCL, OMA, or KEGG Orthology to identify YPK_4186 orthologs across bacterial species

  • Calculate sequence conservation scores to identify highly conserved regions likely crucial for function

  • Map conservation onto predicted structural models to identify potential functional sites

• Synteny analysis:

  • Examine the genomic context of YPK_4186 across different Yersinia species and other bacteria

  • Identify consistently co-located genes that may be functionally related

  • Look for operonic structures that suggest coordinated expression with other genes

• Phylogenetic profiling:

  • Create a presence/absence matrix of YPK_4186 across diverse bacterial genomes

  • Identify other proteins with similar phylogenetic profiles, suggesting functional relationships

  • Correlate profiles with specific phenotypes or ecological niches

• Selection pressure analysis:

  • Calculate dN/dS ratios across the protein sequence to identify regions under purifying or positive selection

  • Compare these patterns between pathogenic and non-pathogenic Yersinia strains

  • Identify specific codons under selection that may be functionally significant

• Horizontal gene transfer analysis:

  • Assess whether YPK_4186 shows evidence of horizontal acquisition

  • Compare codon usage and GC content with genomic averages

  • Determine if YPK_4186 is associated with mobile genetic elements in any species

• Integration with experimental data:

  • Correlate computational findings with experimental results from knockout studies

  • Use comparative genomics predictions to guide targeted mutagenesis experiments

  • Validate predictions about functional sites through biochemical assays

This integrated comparative genomics approach can provide testable hypotheses about YPK_4186 function, evolutionary history, and potential role in Yersinia pathogenicity.

What are the optimal conditions for long-term storage of purified recombinant YPK_4186?

Membrane proteins like YPK_4186 require special consideration for storage to maintain stability and functionality:

• Buffer composition optimization:

  • Use a buffer containing 20-50 mM Tris or HEPES at pH 7.5-8.0

  • Include 100-150 mM NaCl to maintain ionic strength

  • Add 5-10% glycerol to prevent freezing damage and stabilize the protein

  • Consider adding 1-5 mM reducing agent (DTT or TCEP) to prevent oxidation of cysteine residues

  • Include appropriate detergent at concentrations just above CMC (critical micelle concentration)

• Detergent considerations:

  • Mild detergents like DDM, LMNG, or digitonin are often suitable for membrane protein storage

  • Detergent concentration should be maintained above CMC but not excessively high

  • Consider alternative stabilization systems like nanodiscs, amphipols, or SMALPs for improved stability

• Storage temperature:

  • For short-term storage (1-2 weeks): 4°C is often suitable

  • For medium-term storage (1-3 months): -20°C with 25-50% glycerol

  • For long-term storage: -80°C in small aliquots to avoid freeze-thaw cycles

• Stability assessment:

  • Before long-term storage, perform thermal shift assays to identify optimal buffer conditions

  • Monitor sample homogeneity by dynamic light scattering before and after storage

  • Validate functional activity after storage using established assays

• Additional considerations:

  • Add protease inhibitors for storage at 4°C

  • Avoid repeated freeze-thaw cycles by preparing small aliquots

  • Consider lyophilization only if stability in reconstituted form has been confirmed

How can researchers distinguish between properly folded and misfolded recombinant YPK_4186?

Assessing the folding state of membrane proteins like YPK_4186 requires specialized approaches:

• Circular dichroism (CD) spectroscopy:

  • Far-UV CD (190-250 nm) to assess secondary structure content

  • Compare spectra with theoretical predictions based on the protein sequence

  • Monitor thermal denaturation to assess stability and cooperative unfolding

• Fluorescence spectroscopy:

  • Intrinsic tryptophan fluorescence to monitor tertiary structure

  • Use external fluorescent dyes like ANS that bind to exposed hydrophobic regions in misfolded proteins

  • Perform thermal or chemical denaturation studies to generate unfolding curves

• Size-exclusion chromatography (SEC):

  • Analyze elution profiles to detect aggregation or oligomeric states

  • Couple with multi-angle light scattering (SEC-MALS) for accurate molecular weight determination

  • Compare with known standards of similar membrane proteins

• Limited proteolysis:

  • Properly folded membrane proteins typically show resistance to proteolysis in detergent micelles

  • Compare digestion patterns between different preparation methods

  • Identify proteolytically stable domains through mass spectrometry analysis

• Functional assays:

  • Ligand binding studies if potential ligands are known

  • Membrane reconstitution followed by functional assays

  • Interaction studies with known binding partners

• Computational validation:

  • Compare experimental data with AlphaFold2 predictions

  • Use molecular dynamics simulations to assess stability in membrane environments

  • Validate experimental results against similar well-characterized membrane proteins

This multi-technique approach provides robust evidence for the folding state of recombinant YPK_4186, which is crucial for downstream structural and functional studies.

How should researchers design experiments to investigate potential interactions between YPK_4186 and host cells?

Investigating YPK_4186-host interactions requires a comprehensive experimental design:

• Expression profiling during infection:

  • Measure YPK_4186 expression levels during different stages of host cell infection

  • Compare expression in different host cell types (epithelial cells, macrophages)

  • Use qRT-PCR and Western blotting to quantify expression changes

• Localization during host interaction:

  • Create fluorescently tagged YPK_4186 to track localization during infection

  • Use confocal microscopy to determine if YPK_4186 localizes to the host-pathogen interface

  • Perform immunofluorescence studies in fixed infected cells

• Knockout studies in infection models:

  • Create YPK_4186 knockout strains and assess their ability to:

    • Adhere to host cells

    • Invade epithelial cells

    • Survive within macrophages

    • Establish infection in animal models

  • Complement the knockout with wild-type YPK_4186 to confirm phenotypes

• Identification of host interaction partners:

  • Perform bacterial two-hybrid screening against host protein libraries

  • Use cross-linking approaches followed by mass spectrometry

  • Validate potential interactions using co-immunoprecipitation and FRET assays

• Host response analysis:

  • Compare host cell transcriptome responses to wild-type versus YPK_4186 knockout bacteria

  • Measure cytokine production and inflammatory responses

  • Assess host cell cytoskeletal rearrangements and membrane integrity

• Advanced screening approaches:

  • Perform CRISPR screens in host cells to identify genes involved in YPK_4186 interactions

  • Use transposon mutant libraries to identify bacterial genes that modulate YPK_4186 function

  • Develop high-content imaging assays to quantify phenotypic changes

This systematic approach will reveal whether YPK_4186 plays a direct role in host-pathogen interactions and identify the molecular mechanisms involved.

What strategies should be employed to resolve contradictions in experimental data about YPK_4186?

When faced with contradictory data about YPK_4186, researchers should implement the following resolution strategies:

• Systematic review of experimental conditions:

  • Compare buffer compositions, detergents, and protein constructs used across studies

  • Assess expression systems and purification protocols for differences

  • Evaluate the integrity and quality of protein preparations in each study

• Biological variability assessment:

  • Determine if strain-specific differences exist in YPK_4186 sequence or expression

  • Consider host cell variability in interaction studies

  • Assess if contradictions correlate with different experimental models (in vitro vs. in vivo)

• Technical validation:

  • Reproduce key experiments using identical protocols across different laboratories

  • Implement blind experimental design to reduce observer bias

  • Use multiple orthogonal techniques to measure the same parameter

• Statistical reanalysis:

  • Perform meta-analysis of available data when appropriate

  • Consider sample sizes and statistical power in contradictory studies

  • Implement rigorous statistical methods appropriate for the specific data type

• Targeted hypothesis testing:

  • Design experiments specifically aimed at resolving the contradiction

  • Create experimental conditions that bridge differences between contradictory studies

  • Test whether specific variables explain the observed contradictions

• Computational modeling:

  • Develop mathematical models incorporating competing hypotheses

  • Use systems biology approaches to predict conditions under which different outcomes occur

  • Generate new hypotheses that might explain seemingly contradictory results

• Expert consultation:

  • Organize focused discussions with researchers who produced contradictory results

  • Consider collaborative experiments between groups with differing results

  • Implement standardized protocols agreed upon by multiple research groups