Recombinant UPF0114 protein YqhA (yqhA)

What is UPF0114 protein YqhA and in which organisms is it found?

UPF0114 protein YqhA is a bacterial protein classified in the UPF (Uncharacterized Protein Family) 0114 group. It has been identified in several Gram-negative bacterial species, including Shigella dysenteriae, Salmonella paratyphi A, and Escherichia coli. Shigella dysenteriae, first discovered in 1897, is a non-motile, facultative aerobic, rod-shaped bacterium that causes disease in primates but not other mammals. It's closely related to E. coli and is one of the leading bacterial causes of diarrhea worldwide . The protein is particularly found in pathogenic strains like Salmonella paratyphi A (strain AKU_12601) and Escherichia coli O7:K1 (strain IAI39 / ExPEC), suggesting potential involvement in bacterial pathogenicity .

What are the gene identifiers and nomenclature for YqhA?

The gene encoding YqhA is officially named "yqhA". In Salmonella paratyphi A, it has the ordered locus name SSPA2818 according to genome annotation . For Escherichia coli O7:K1 (strain IAI39 / ExPEC), the protein can be found in the UniProt database under accession number B7NJ05 . The gene is consistently named "yqhA" across different bacterial species, indicating evolutionary conservation of this genetic element.

What purification methods are most effective for recombinant YqhA?

While specific purification protocols are not detailed in the available data, standard methodologies for membrane-associated bacterial proteins would be applicable. Based on general principles for similar proteins, a multi-step purification process would typically include:

• Cell lysis under conditions that solubilize membrane proteins (detergent-based)

• Initial purification using affinity chromatography (utilizing tags determined during production)

• Further purification through size exclusion or ion-exchange chromatography

• Final polishing step if needed

The commercially available YqhA products have documented purity levels of >85% as determined by SDS-PAGE , suggesting that high purity can be achieved with appropriate methodology.

What are the optimal storage conditions for maintaining YqhA stability?

For optimal stability of recombinant YqhA protein, storage at -20°C is recommended for routine use, with -80°C preferable for extended storage periods. The protein is typically maintained in a Tris-based buffer with 50% glycerol to optimize stability . Working aliquots should be stored at 4°C and used within one week, as repeated freeze-thaw cycles can compromise protein integrity and are specifically not recommended . For lyophilized preparations, a shelf life of approximately 12 months at -20°C/-80°C can be expected, while liquid formulations typically remain stable for about 6 months under similar conditions .

What is the predicted membrane topology of YqhA protein?

Based on the amino acid sequence analysis of YqhA from Salmonella paratyphi A, the protein contains multiple hydrophobic regions consistent with transmembrane domains. The sequence "MERFLENVMYASRWLLAPVYFGLSLALIALALKFFQEILHVLPNVFALAEADLILVLLSLVDMTLVGGLLVMVMFSGYENFVSQLDISAGKEKLNWLGKMDATSLKNKVAASIVAISSIHLLRVFMDAKNVPDNKLMWYVIIHLTFVLSAFVMGYLDRLTRHNH" suggests a membrane protein with several potential transmembrane helices . The high proportion of hydrophobic amino acids (including leucine, isoleucine, valine, and phenylalanine) and the presence of motifs like "SLALIALALK" are characteristic of membrane-spanning regions.

What functional domains have been identified in YqhA?

YqhA belongs to the UPF0114 protein family, a group of proteins whose functions are not yet fully characterized (hence the "Uncharacterized Protein Family" designation). While specific functional domains have not been explicitly identified in the available data, sequence analysis and comparison with similar bacterial membrane proteins suggest potential roles in:

• Membrane transport or channel activity

• Signal transduction

• Cell envelope integrity

• Response to environmental stressors

Further experimental characterization through site-directed mutagenesis and functional assays would be required to definitively identify functional domains.

How does YqhA structure compare across different bacterial species?

A comparative analysis of YqhA sequences from Shigella dysenteriae, Salmonella paratyphi A, and Escherichia coli would likely reveal high conservation, given their close evolutionary relationships. Shigella is closely related to E. coli, with significant genomic similarity . The conservation of the gene name (yqhA) and classification (UPF0114) across these species suggests structural and functional conservation. A detailed sequence alignment would identify conserved residues that may be critical for protein function and could guide site-directed mutagenesis studies.

How can recombinant YqhA be used in vaccine development research?

Recombinant YqhA protein has potential applications in vaccine development, particularly for Shigella dysenteriae, which is one of the leading bacterial causes of diarrhea worldwide . For vaccine research applications, consider the following methodological approach:

• Antigen preparation: Express and purify recombinant YqhA at high purity (>90%)

• Immunogenicity assessment:

  • Evaluate antibody production in animal models

  • Assess both humoral and cell-mediated immune responses

• Protection studies:

  • Challenge immunized animals with virulent bacterial strains

  • Evaluate protection metrics including bacterial load, clinical scores, and survival

• Formulation optimization:

  • Test various adjuvants to enhance immunogenicity

  • Evaluate different delivery routes (subcutaneous, intranasal, oral)

The use of properly folded, full-length protein is critical for mimicking native epitopes and generating protective immunity.

What protocols are recommended for structural studies of YqhA?

For structural characterization of YqhA, consider a multi-technique approach:

• X-ray crystallography preparation:

  • Express protein with optimal tags for crystallization

  • Use detergent screening to identify conditions that maintain native conformation while promoting crystal formation

  • Implement vapor diffusion techniques with various precipitants

• NMR spectroscopy:

  • Isotopically label protein (15N, 13C) during expression

  • Optimize sample conditions (temperature, pH, salt concentration)

  • Acquire multi-dimensional spectra for backbone and side-chain assignments

• Cryo-electron microscopy:

  • Prepare protein in detergent micelles or nanodiscs

  • Apply to grids with optimal ice thickness

  • Collect data at various defocus values

Each method requires specific sample preparation techniques and has distinct advantages for membrane protein structural analysis.

How can molecular dynamics simulations complement experimental studies of YqhA?

Molecular dynamics (MD) simulations provide valuable insights into protein behavior that may be difficult to observe experimentally. For YqhA research, MD simulations can:

• Predict stability of transmembrane domains in lipid bilayers

• Identify potential conformational changes during function

• Evaluate effects of mutations on protein dynamics

• Model interactions with potential binding partners or substrates

The simulation protocol should include:

Results from MD simulations should be validated against experimental data whenever possible and can guide the design of future experiments.

What are common challenges in expressing recombinant YqhA and how can they be addressed?

Expression of membrane proteins like YqhA presents several challenges. Common issues and their solutions include:

• Low expression levels:

  • Optimize codon usage for expression host

  • Test different promoters (T7, tac, arabinose-inducible)

  • Reduce expression temperature (18-25°C)

  • Use specialized E. coli strains (C41/C43, Lemo21)

• Protein misfolding and aggregation:

  • Co-express with chaperones (GroEL/GroES, DnaK)

  • Include fusion partners (MBP, SUMO, Trx)

  • Optimize induction conditions (lower IPTG concentration, slower induction)

  • Screen detergents for solubilization

• Degradation during expression:

  • Use protease-deficient strains

  • Include protease inhibitors during purification

  • Optimize cell lysis conditions

For YqhA specifically, expression in E. coli appears to be feasible , though optimization may be required for high yields of functional protein.

How can researchers verify the proper folding and functionality of purified YqhA?

Assessing proper folding and functionality of membrane proteins like YqhA requires multiple analytical approaches:

• Biophysical characterization:

  • Circular dichroism (CD) spectroscopy to assess secondary structure content

  • Thermal shift assays to evaluate stability

  • Size exclusion chromatography to confirm monodispersity

• Functional assays (based on predicted functions):

  • Liposome reconstitution and permeability assays

  • Binding studies with potential interaction partners

  • Activity assays if enzymatic function is identified

• Structural integrity:

  • Limited proteolysis to evaluate compact folding

  • Tryptophan/tyrosine fluorescence for tertiary structure assessment

The specific assays would need to be adapted once the function of YqhA is better characterized.

What quality control measures are essential before using YqhA in critical experiments?

Before using purified YqhA in downstream applications, implement these quality control measures:

• Purity assessment:

  • SDS-PAGE with both Coomassie and silver staining (aim for >90% purity)

  • Western blot with anti-tag or specific antibodies

  • Mass spectrometry to confirm protein identity and detect contaminants

• Homogeneity evaluation:

  • Dynamic light scattering to assess aggregation state

  • Size exclusion chromatography with multi-angle light scattering

  • Analytical ultracentrifugation for oligomeric state determination

• Stability testing:

  • Short-term stability at experimental conditions

  • Freeze-thaw stability if storage is required

  • Assessment after buffer exchange or concentration

Following recommended storage guidelines is essential: -20°C for routine storage, -80°C for long-term, with 50% glycerol as a cryoprotectant, and avoiding repeated freeze-thaw cycles .

How conserved is YqhA across different bacterial pathogens?

YqhA appears in multiple pathogenic bacteria, including Shigella dysenteriae, Salmonella paratyphi A, and Escherichia coli O7:K1 . This conservation suggests functional importance, possibly in pathogenicity or basic cellular processes. Researchers should consider performing multiple sequence alignments and phylogenetic analyses to identify highly conserved residues, which may indicate functional importance. The UPF0114 classification across these species further supports evolutionary conservation of this protein family.

What approaches are recommended for studying potential roles of YqhA in pathogenesis?

To investigate YqhA's potential role in bacterial pathogenesis, consider these methodological approaches:

• Gene knockout studies:

  • Generate yqhA deletion mutants using CRISPR-Cas9 or homologous recombination

  • Assess phenotypic changes in growth, stress response, and virulence

  • Perform complementation studies to confirm specificity

• Infection models:

  • Compare wild-type and yqhA mutant strains in cell culture infection models

  • Evaluate adhesion, invasion, and intracellular survival

  • Assess impact on host immune response (cytokine production, inflammasome activation)

• Interaction studies:

  • Identify protein-protein interactions using pull-down assays or bacterial two-hybrid systems

  • Characterize interactions with host factors using techniques like BioID or APEX proximity labeling

  • Validate interactions with co-immunoprecipitation and microscopy

These approaches can provide insights into whether YqhA contributes to virulence and host-pathogen interactions.