Recombinant Escherichia fergusonii UPF0761 membrane protein yihY (yihY)

What is the UPF0761 membrane protein yihY and what organisms express it?

UPF0761 membrane protein yihY is a conserved membrane protein found in several Escherichia species, including E. fergusonii and various strains of E. coli. The protein consists of 290 amino acids and is encoded by the yihY gene . The "UPF" designation (Uncharacterized Protein Family) indicates that this protein's function has not been fully characterized, though it is classified as a membrane protein based on sequence analysis and predicted structure .

The protein is expressed in:

• Escherichia fergusonii (strain ATCC 35469 / DSM 13698 / CDC 0568-73)

• Various E. coli strains including O17:K52:H18, O45:K1, and SMS-3-5

What is known about Escherichia fergusonii as a research model?

Escherichia fergusonii is a species closely related to E. coli (with 64% DNA hybridization similarity to E. coli-Shigella group) and has emerged as an important research model for several reasons :

• Clinical relevance: E. fergusonii has been isolated from patients with various conditions including diarrhea, urinary tract infections, bacteremia, and wound infections .

• Antimicrobial resistance: Multiple studies have documented multidrug-resistant E. fergusonii strains, making it an important model for studying antimicrobial resistance mechanisms .

• Virulence factors: Recent research has identified virulence factors in E. fergusonii, including the first isolation of heat-labile enterotoxin 1 (LT1) producing strain from a patient with diarrhea in Japan .

• Genomic research: Complete genome sequences of several E. fergusonii strains have been determined, enabling comparative genomics studies .

• Veterinary importance: E. fergusonii has been isolated from various animals with clinical conditions, including dairy cattle with diarrhea .

• Genetic engineering potential: E. fergusonii has been successfully engineered to express specific metabolic pathways, demonstrating its utility as a genetic engineering platform .

What expression systems are most effective for recombinant production of E. fergusonii yihY protein?

Based on the available research data, several expression systems have been successfully used for recombinant production of E. fergusonii yihY protein:

• E. coli-based expression systems: Most commercial recombinant yihY proteins are expressed in E. coli, which appears to be an effective heterologous expression system . This is likely due to the close genomic relationship between E. fergusonii and E. coli.

• Yeast expression systems: Some suppliers report using yeast-based expression systems for recombinant yihY production . This alternative may be valuable when post-translational modifications are required.

For optimal expression, researchers should consider the following methodological approaches:

• Tags and fusion partners: His-tagged versions of the protein facilitate purification and detection. The tag placement (N-terminal or C-terminal) may be determined during the production process based on protein stability considerations .

• Expression conditions: Since yihY is a membrane protein, expression conditions should be optimized to prevent aggregation and misfolding. Consider using lower induction temperatures (16-25°C) and specialized E. coli strains designed for membrane protein expression.

• Solubilization strategies: As a membrane protein, appropriate detergents will be needed for solubilization during purification. The specific detergents should be selected based on downstream applications.

What purification methods yield the highest purity for recombinant yihY protein?

Based on commercial production protocols, the following purification strategies have proven effective for recombinant yihY:

• Affinity chromatography: His-tagged versions of the protein can be purified using immobilized metal affinity chromatography (IMAC) .

• Quality control methods: SDS-PAGE analysis is commonly used to verify purity, with commercial preparations typically achieving >85-90% purity .

A recommended purification workflow:

• Cell lysis under conditions optimized for membrane proteins

• Membrane fraction isolation via ultracentrifugation

• Detergent solubilization of membrane proteins

• IMAC purification of His-tagged protein

• Size exclusion chromatography as a polishing step

• Quality assessment via SDS-PAGE and/or Western blotting

What storage conditions maintain stability of recombinant yihY protein?

According to multiple commercial sources, the following storage conditions are recommended for maintaining the stability of recombinant yihY protein:

• Short-term storage: Store working aliquots at 4°C for up to one week .

• Long-term storage: Store at -20°C or -80°C .

• Storage buffer composition: Tris-based buffer with 50% glycerol, pH optimized for this specific protein .

• Handling precautions:

  • Avoid repeated freeze-thaw cycles

  • Centrifuge vials briefly before opening

  • Reconstitute lyophilized protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL

  • Consider adding glycerol (5-50% final concentration) for storage

The shelf life is approximately 6 months for liquid formulations at -20°C/-80°C and approximately 12 months for lyophilized preparations at -20°C/-80°C .

How can researchers validate the identity and activity of recombinant yihY protein?

While the search results don't provide specific activity assays for yihY (consistent with its UPF designation as an uncharacterized protein), researchers can validate the identity and integrity of the recombinant protein through several methods:

• Mass spectrometry analysis: Perform peptide mass fingerprinting or LC-MS/MS to confirm the amino acid sequence matches that of yihY.

• Western blotting: Use antibodies against the protein tag (e.g., anti-His antibody) or develop specific antibodies against yihY.

• Sequence verification: Confirm the DNA sequence of the expression construct before protein production.

• Membrane localization studies: As yihY is a membrane protein, researchers can verify its proper localization in membrane fractions using subcellular fractionation techniques followed by Western blotting.

• Size exclusion chromatography: Verify that the protein exists in an appropriately folded state rather than as aggregates.

For functional validation, researchers may need to develop assays based on hypothesized functions or interactions, as the specific function of yihY remains to be fully characterized.

What methods are effective for studying membrane localization and topology of yihY?

As a membrane protein, understanding the localization and topology of yihY is critical. The following methods can be employed:

• Hydropathy plot analysis: Computational prediction of transmembrane domains based on the amino acid sequence.

• Fluorescent protein fusion: Creating fusions with fluorescent proteins (GFP/RFP) at either terminus to visualize cellular localization.

• Protease protection assays: Determining which regions of the protein are protected by the membrane.

• Cysteine scanning mutagenesis: Introducing cysteine residues at different positions to be labeled with membrane-impermeable reagents.

• Epitope insertion: Inserting epitope tags at various positions to determine which regions are accessible for antibody binding.

• Electron microscopy: Using immunogold labeling to visualize the protein's location in the membrane.

• Structural studies: Employing techniques like cryo-EM or X-ray crystallography after detergent solubilization or reconstitution into nanodiscs or liposomes.

What experimental approaches can elucidate the function of yihY in E. fergusonii?

Since yihY is classified as an uncharacterized protein (UPF), determining its function requires a multi-faceted approach:

• Gene knockout/knockdown studies: Creating yihY deletion mutants in E. fergusonii to observe phenotypic changes. This may reveal whether the protein is essential and what cellular processes it affects.

• Protein-protein interaction studies:

  • Co-immunoprecipitation to identify binding partners

  • Bacterial two-hybrid screening

  • Proximity labeling techniques like BioID or APEX2

• Transcriptomic and proteomic analysis: Compare wild-type to yihY knockout strains to identify pathways affected by its absence.

• Metabolomic profiling: Identify metabolic changes in yihY mutants.

• Genetic context analysis: Examining the genomic neighborhood of yihY for functionally related genes.

• Cross-species complementation: Testing if yihY can complement the deletion of homologous genes in related species.

• Structural prediction and modeling: Using computational approaches to predict function based on structural features.

How does E. fergusonii yihY compare structurally and functionally to homologs in other bacterial species?

While specific comparative data for yihY is limited in the search results, sequence analysis shows that the yihY protein is conserved among various Escherichia species:

• Sequence similarity: The yihY protein sequences from E. fergusonii, E. coli O17:K52:H18, and E. coli O45:K1 show high similarity with only minor variations in specific amino acid residues .

• Potential functional conservation: The high sequence conservation suggests functional conservation, though specific functions remain to be fully characterized.

For researchers wanting to conduct comparative analyses:

• Phylogenetic analysis: Perform multiple sequence alignment and construct phylogenetic trees to understand the evolutionary relationships of yihY across different bacterial species.

• Structural modeling: Use homology modeling to predict potential structural differences between yihY proteins from different species.

• Domain architecture analysis: Compare the arrangement of predicted functional domains across species.

• Cross-species complementation experiments: Test whether yihY from one species can functionally replace the homolog in another species.

What is the potential role of yihY in E. fergusonii virulence and pathogenicity?

Given that E. fergusonii has been isolated from various clinical infections, researchers may want to investigate the potential role of yihY in virulence and pathogenicity . Though direct evidence linking yihY to virulence is not provided in the search results, several experimental approaches could be employed:

• Virulence model comparison: Compare the virulence of wild-type E. fergusonii to yihY knockout mutants in appropriate infection models.

• Expression analysis during infection: Monitor yihY expression levels during different stages of infection to determine if it is differentially regulated.

• Host-pathogen interaction studies: Investigate if yihY interacts with host factors during infection.

• Co-expression analysis: Determine if yihY expression correlates with known virulence factors such as the heat-labile enterotoxin (LT1) identified in some E. fergusonii strains .

• Stress response role: Investigate if yihY plays a role in bacterial survival under host-induced stress conditions (e.g., oxidative stress, antimicrobial peptides).

What bioinformatic approaches can predict the structural features and potential functions of yihY?

For uncharacterized proteins like yihY, bioinformatic approaches can provide valuable insights:

• Sequence-based predictions:

  • Transmembrane domain prediction using tools like TMHMM, Phobius, or TOPCONS

  • Signal peptide prediction using SignalP

  • Conserved domain identification using CDD, Pfam, or InterPro

  • Secondary structure prediction using PSIPRED

• Structure prediction:

  • AlphaFold2 for accurate 3D structure prediction

  • Template-based modeling using homologous proteins of known structure

  • Ab initio modeling for regions lacking homology to known structures

• Functional prediction:

  • Gene neighborhood analysis to identify functional associations

  • Co-expression network analysis

  • Protein-protein interaction prediction

  • Gene Ontology term prediction

• Evolutionary analysis:

  • Identification of conserved residues through multiple sequence alignments

  • Positive selection analysis to identify adaptively evolving sites

  • Ancestry reconstruction to understand the protein's evolutionary history

How does research on E. fergusonii yihY contribute to understanding antimicrobial resistance?

E. fergusonii has been identified as an emerging multidrug-resistant pathogen in both human and animal infections . While the specific role of yihY in antimicrobial resistance is not directly established in the search results, researchers can investigate this relationship through:

• Comparative expression analysis: Compare yihY expression levels between antibiotic-resistant and susceptible strains.

• Gene knockout studies: Determine if yihY deletion affects susceptibility to various antibiotics.

• Structural analysis: Investigate if yihY could be a novel target for antimicrobial development.

• Membrane permeability studies: As a membrane protein, yihY may influence membrane permeability and thus antibiotic uptake or efflux.

The search results document antimicrobial resistance patterns in E. fergusonii isolates:

What methodological challenges exist in studying membrane proteins like yihY?

Membrane proteins present unique challenges that researchers should consider when studying yihY:

• Expression challenges:

  • Toxicity to expression hosts

  • Proper membrane insertion and folding

  • Low expression yields compared to soluble proteins

• Purification difficulties:

  • Requirement for detergents or membrane mimetics

  • Protein stability outside the native membrane environment

  • Detergent selection affecting protein structure and function

• Structural analysis limitations:

  • Challenges in crystallization for X-ray crystallography

  • Size limitations for NMR studies

  • Conformational heterogeneity affecting cryo-EM reconstruction

• Functional assay development:

  • Maintaining native-like environment for functional studies

  • Reconstitution into artificial membranes or liposomes

  • Potential requirement for specific lipids or membrane composition

Methodological approaches to address these challenges include:

• Using specialized expression hosts designed for membrane proteins

• Employing fusion partners that enhance membrane protein expression

• Developing native membrane isolation techniques

• Utilizing nanodiscs or other membrane mimetics for structural and functional studies

How can researchers leverage E. fergusonii as a model for studying host-pathogen interactions?

E. fergusonii has been isolated from various clinical sources and has demonstrated pathogenic potential in both humans and animals . Researchers can leverage this organism as a model for studying host-pathogen interactions through:

• Infection models:

  • Development of animal models that recapitulate E. fergusonii infections

  • Cell culture models to study bacterial adhesion, invasion, and intracellular survival

  • Ex vivo tissue models to study tissue-specific interactions

• Virulence factor characterization:

  • Identification and characterization of virulence factors like the recently discovered heat-labile enterotoxin 1 (LT1)

  • Investigation of yihY's potential role in virulence

• Host response studies:

  • Analysis of host immune responses to E. fergusonii infection

  • Identification of host factors that interact with bacterial components

• Comparative pathogenomics:

  • Genomic comparison between clinical and environmental isolates

  • Identification of genetic elements associated with virulence

• One Health approach:

  • Understanding E. fergusonii's role in both human and animal infections

  • Investigation of potential zoonotic transmission

What are the most promising future research directions for understanding yihY function?

Given the current state of knowledge about yihY as an uncharacterized membrane protein, several promising research directions emerge:

• Comprehensive functional characterization:

  • Gene knockout phenotyping under various growth conditions

  • High-throughput screening for conditions where yihY becomes essential

  • Identification of interaction partners through proteomic approaches

• Structural biology approaches:

  • Cryo-EM or X-ray crystallography to determine 3D structure

  • Structure-guided functional hypotheses

  • Molecular dynamics simulations to understand membrane interactions

• Systems biology integration:

  • Transcriptomic and proteomic profiling to position yihY in cellular networks

  • Metabolomic analysis to identify affected metabolic pathways

  • Network analysis to predict functional relationships

• Clinical and environmental significance:

  • Investigation of yihY expression in clinical versus environmental isolates

  • Correlation with virulence or antibiotic resistance phenotypes

  • Potential as a diagnostic biomarker for specific E. fergusonii strains

• Comparative analysis across species:

  • Functional conservation between yihY homologs in different bacterial species

  • Evolutionary analysis to identify selective pressures