Recombinant Yersinia enterocolitica serotype O:8 / biotype 1B Probable intracellular septation protein A (YE2220)

What is YE2220 and what is its primary function in Yersinia enterocolitica?

YE2220, also known as Probable intracellular septation protein A or inner membrane-spanning protein YciB, is a small hydrophobic protein consisting of 180 amino acids found in Yersinia enterocolitica serotype O:8 / biotype 1B . Based on homology studies with similar proteins in related bacterial species, YE2220 appears to function primarily in bacterial cell division and septum formation. The protein shares functional similarity with the ispA gene product in Shigella flexneri, which has been shown to be essential for proper cell division and septum formation . When the related ispA gene is mutated in Shigella, it results in filamentous bacteria lacking proper septa, suggesting a critical role in the cell division process .

What is the cellular localization and topology of YE2220 protein?

YE2220 is predominantly localized in the bacterial inner membrane, as indicated by its highly hydrophobic amino acid sequence and classification as an "inner membrane-spanning protein" . Analysis of its amino acid sequence (MKQLLDFLPLVVFFVFYKMYDIFVASGALIVATLLALAFTWFKYRKVEKMTLVTAIMVLVFGTLTLAFHSDLFIKWKVTVLYVLFAVALLVSQWFMKKPLIQRMLGKELTLPDTVWSTLNMSWAVFFLVCGLLNIYVAFWLPQDIWVNFKVFGLTALTLVFTLISGVYIYRHMPEEQKKS) reveals multiple transmembrane domains consistent with an integral membrane protein . This membrane localization is critical for its function in septum formation during bacterial cell division. The protein likely spans the membrane multiple times with specific domains extending into the cytoplasm and periplasmic space, enabling it to participate in the complex process of coordinating cell division.

How is YE2220 related to bacterial pathogenesis?

While direct evidence for YE2220's role in Yersinia enterocolitica pathogenesis is still being elucidated, insights can be drawn from studies on homologous proteins in related pathogens. In Shigella flexneri, the ispA gene (homologous to YE2220) has been identified as an essential virulence gene . Mutation of ispA in S. flexneri resulted in an avirulent phenotype where bacteria were unable to spread throughout epithelial cell monolayers . The mutant initially spread intercellularly at rates comparable to wild-type but gradually slowed and stopped spreading due to defects in cell division . Additionally, the mutation affected the bacteria's ability to polymerize actin, a prerequisite for intra- and inter-cellular spreading . By extension, YE2220 likely plays a similar role in Yersinia enterocolitica virulence, potentially affecting its ability to divide properly within host cells and spread during infection.

What are the optimal conditions for reconstituting lyophilized recombinant YE2220 protein?

For optimal reconstitution of lyophilized recombinant YE2220 protein, follow these methodological steps:

• Briefly centrifuge the vial containing lyophilized protein to ensure all material is at the bottom of the vial .

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

• For long-term storage stability, add glycerol to a final concentration of 5-50% (50% is recommended as the default concentration) .

• Aliquot the reconstituted protein to avoid repeated freeze-thaw cycles, which can compromise protein integrity .

• Store reconstituted aliquots at -20°C/-80°C for long-term storage, or at 4°C for up to one week if planning immediate use .

Since YE2220 is a membrane protein, consider adding mild detergents (such as n-dodecyl-β-D-maltoside or CHAPS) to the reconstitution buffer if functional studies require the protein to maintain its native conformation. The reconstituted protein should be handled carefully to prevent denaturation, particularly given its hydrophobic nature.

How can researchers validate the functional activity of recombinant YE2220?

Validating the functional activity of recombinant YE2220 requires multiple approaches due to its membrane protein nature and septation-related function:

• Complementation assays: Test whether the recombinant protein can complement YE2220 knockout/mutant strains of Yersinia enterocolitica, restoring normal cell morphology and division patterns. Similar assays with the ispA gene in Shigella demonstrated that the wild-type gene could complement the functional defects in mutant strains .

• Microscopy analysis: Perform fluorescence microscopy with membrane stains to assess the protein's localization to the bacterial septum during cell division.

• Protein interaction studies: Use pull-down assays or co-immunoprecipitation to identify interactions with known septation and cell division proteins.

• In vitro membrane incorporation: Confirm the protein's ability to incorporate into artificial membrane systems, which is crucial for its function.

• Cell division phenotype analysis: In cellular systems, observe whether the presence of functional YE2220 prevents the filamentous growth characteristic of bacteria with septation defects, similar to what was observed with ispA mutants in Shigella .

Remember that the purity of the recombinant protein should be greater than 90% as determined by SDS-PAGE to ensure reliable results in functional assays .

What experimental models are most appropriate for studying YE2220 function?

Several experimental models can be employed to study YE2220 function effectively:

• Bacterial genetic systems: Utilize gene knockout, knockdown, or overexpression systems in Yersinia enterocolitica to study the effects of YE2220 modulation on bacterial physiology and pathogenesis.

• Cell culture infection models: Employ epithelial cell monolayers (similar to those used in Shigella studies) to assess the role of YE2220 in bacterial invasion, intracellular replication, and cell-to-cell spread .

• Reconstituted membrane systems: Use liposomes or nanodiscs incorporating purified YE2220 to study its membrane interactions and potential oligomerization.

• Heterologous expression systems: Express YE2220 in E. coli or other model bacteria to study its effects on cell division in different contexts. The protein has been successfully expressed in E. coli systems as indicated in the product information .

• Animal infection models: For advanced in vivo studies, appropriate animal models of Yersinia infection can be used to assess the contribution of YE2220 to virulence, particularly focusing on bacterial dissemination in tissues.

When selecting an experimental model, consider the specific aspect of YE2220 function you aim to investigate, whether it's basic biochemical properties, cell division mechanisms, or virulence-related functions.

What is the relationship between YE2220 structure and its function in bacterial cell division?

The structure-function relationship of YE2220 can be inferred from its amino acid sequence and homology to related proteins:

The 180-amino acid sequence of YE2220 (MKQLLDFLPLVVFFVFYKMYDIFVASGALIVATLLALAFTWFKYRKVEKMTLVTAIMVLVFGTLTLAFHSDLFIKWKVTVLYVLFAVALLVSQWFMKKPLIQRMLGKELTLPDTVWSTLNMSWAVFFLVCGLLNIYVAFWLPQDIWVNFKVFGLTALTLVFTLISGVYIYRHMPEEQKKS) reveals a highly hydrophobic protein with multiple predicted transmembrane domains . This hydrophobicity is consistent with its role as an integral membrane protein and similar to the characteristics observed in the homologous ispA gene product in Shigella, which was described as a "small (21 kDa), very hydrophobic protein" .

The protein likely functions through specific interactions with other cell division proteins at the septation site. The hydrophobic transmembrane regions anchor the protein in the cell membrane, while hydrophilic loops may interact with cytoplasmic or periplasmic components of the cell division machinery. The exact structural domains responsible for specific functions (such as recruitment to the division site or interaction with other septation proteins) have not been fully characterized and represent an important area for future research.

Advanced structural studies using techniques such as X-ray crystallography or cryo-electron microscopy would provide valuable insights into how the three-dimensional structure of YE2220 facilitates its role in bacterial septation.

How does YE2220 interact with the bacterial cell division machinery?

YE2220 likely interacts with multiple components of the bacterial cell division machinery, although specific interaction partners have not been comprehensively identified. Based on functional similarity to the ispA gene product in Shigella, several hypothetical interaction mechanisms can be proposed:

• FtsZ interaction: YE2220 may interact directly or indirectly with FtsZ, the bacterial tubulin homolog that forms the Z-ring at the division site.

• Membrane remodeling: The protein may facilitate membrane invagination during septum formation through interactions with phospholipids or membrane-remodeling enzymes.

• Peptidoglycan synthesis coordination: YE2220 could coordinate peptidoglycan synthesis at the division site through interactions with cell wall synthesis enzymes.

• Divisome recruitment: The protein may function in recruiting other divisome components to the septation site.

The defects observed in ispA mutants of Shigella, which form long filamentous bacteria lacking septa , suggest that the protein plays a critical role in the proper assembly or function of the division machinery. Research approaches to identify specific interaction partners could include bacterial two-hybrid screens, co-immunoprecipitation followed by mass spectrometry, or fluorescence microscopy to identify co-localization with known divisome components.

What molecular mechanisms link YE2220 function to bacterial virulence?

The connection between YE2220 function and bacterial virulence likely involves several molecular mechanisms:

• Cell division during infection: Proper bacterial cell division, mediated by YE2220, is crucial for maintaining optimal bacterial numbers during infection. The ispA mutant in Shigella was unable to spread throughout epithelial cell monolayers due to increasing defects in cell division .

• Actin polymerization: The ispA mutation in Shigella affected the bacteria's ability to polymerize actin , a process essential for intercellular spread during infection. YE2220 may similarly influence actin-based motility in Yersinia, either directly or through effects on other bacterial factors.

• Stress adaptation: Proper septation may be particularly important for bacteria to adapt to stress conditions encountered during infection.

• Membrane integrity: As a membrane protein, YE2220 may influence membrane properties that affect sensitivity to host defense mechanisms or antimicrobial compounds.

Research focusing on the intersection of cell division and virulence factors would be valuable for understanding how fundamental cellular processes like septation contribute to bacterial pathogenesis. Comparative studies between wild-type and YE2220 mutant strains in infection models could reveal specific virulence phenotypes associated with YE2220 dysfunction.

What are the challenges in expressing and purifying recombinant YE2220?

Expressing and purifying membrane proteins like YE2220 presents several technical challenges:

• Membrane protein solubility: The highly hydrophobic nature of YE2220 can lead to protein aggregation and inclusion body formation during expression.

• Maintaining native conformation: Ensuring the protein retains its native fold and activity during extraction from membranes and subsequent purification steps is challenging.

• Expression system selection: While E. coli has been successfully used for YE2220 expression , optimization of expression conditions (temperature, induction parameters, and strain selection) is crucial for maximizing yield.

• Purification strategy: Effective purification typically requires careful detergent selection for solubilization and may benefit from the His-tag incorporated in recombinant constructs .

• Protein stability: Once purified, maintaining stability during storage is critical, with recommendations including lyophilization in Tris/PBS-based buffer with 6% trehalose at pH 8.0 .

To overcome these challenges, researchers should consider:

• Using specialized E. coli strains designed for membrane protein expression

• Optimizing induction conditions (lower temperatures, reduced inducer concentrations)

• Screening multiple detergents for optimal solubilization

• Utilizing the incorporated His-tag for affinity purification

• Implementing quality control steps to verify protein integrity and purity (>90% by SDS-PAGE)

How can researchers design effective knockout experiments to study YE2220 function?

Designing effective knockout experiments for YE2220 requires careful consideration of several factors:

• Knockout strategy selection:

  • Complete gene deletion using homologous recombination

  • CRISPR-Cas9 mediated genome editing

  • Insertion mutagenesis (similar to the Tn10 mutagenesis used in Shigella ispA studies)

  • Conditional knockout systems for essential genes

• Phenotypic validation:

  • Microscopic examination for filamentous morphology and septation defects

  • Growth curve analysis to identify division abnormalities

  • Complementation assays to confirm phenotype specificity

• Experimental controls:

  • Wild-type strain controls

  • Complementation with wild-type YE2220 to rescue phenotypes

  • Controls for polar effects on neighboring genes

• Advanced phenotypic characterization:

  • Electron microscopy to visualize septum formation

  • Fluorescent D-amino acid labeling to monitor peptidoglycan synthesis

  • Live-cell imaging to track division dynamics

  • Virulence assays in cell culture models

When interpreting results, researchers should consider that complete knockout may be lethal if the gene is essential, as suggested by the severe growth defects in ispA mutants of Shigella . In such cases, conditional knockout systems or partial loss-of-function mutations may be more informative.

What analytical techniques are most suitable for studying YE2220 interactions with other proteins?

Several analytical techniques are particularly valuable for studying interactions of membrane proteins like YE2220:

• Membrane-based protein-protein interaction techniques:

  • Split-ubiquitin membrane yeast two-hybrid system

  • Bacterial two-hybrid systems adapted for membrane proteins

  • FRET/BRET analysis in bacterial systems

  • Proximity labeling approaches (BioID, APEX)

• Biochemical approaches:

  • Co-immunoprecipitation with membrane-compatible detergents

  • Pull-down assays using His-tagged YE2220

  • Chemical crosslinking followed by mass spectrometry

  • Label transfer proximity assays

• Structural and biophysical methods:

  • Hydrogen-deuterium exchange mass spectrometry

  • Surface plasmon resonance with membrane mimetics

  • Microscale thermophoresis

  • Isothermal titration calorimetry adapted for membrane proteins

• Imaging approaches:

  • Super-resolution microscopy to track co-localization

  • Fluorescence correlation spectroscopy

  • Single-molecule tracking in live bacteria

When designing interaction studies, consider that membrane proteins like YE2220 require special handling to maintain their native environment. The use of mild detergents, membrane mimetics (nanodiscs, liposomes), or in-cell approaches can help preserve physiologically relevant interactions that might be disrupted in more harsh extraction conditions.

What are promising approaches for elucidating the three-dimensional structure of YE2220?

Determining the structure of membrane proteins like YE2220 presents unique challenges. Several promising approaches include:

• X-ray crystallography: While challenging for membrane proteins, successful crystallization might be achieved using:

  • Lipidic cubic phase crystallization

  • Detergent screening for optimal solubilization

  • Fusion with crystallization chaperones

  • Antibody fragment co-crystallization to stabilize specific conformations

• Cryo-electron microscopy (cryo-EM): Increasingly powerful for membrane proteins, especially when:

  • Reconstituted into nanodiscs or amphipols

  • Assembled into larger complexes with binding partners

  • Combined with computational approaches for smaller proteins

• NMR spectroscopy: Suitable for smaller membrane proteins or domains:

  • Solution NMR with detergent-solubilized protein

  • Solid-state NMR with reconstituted membranes

  • Selective isotope labeling to focus on specific regions

• Integrative structural biology:

  • Combining lower-resolution techniques with computational modeling

  • Cross-linking mass spectrometry to identify distance constraints

  • Evolutionary coupling analysis to predict contacts between residues

• AlphaFold and other AI-based structure prediction: Recent advances in protein structure prediction may provide valuable structural models, especially when combined with experimental validation.

Success in structural studies would significantly advance understanding of YE2220 function by revealing the spatial arrangement of transmembrane domains and potential interaction surfaces relevant to septation and cell division.

How might YE2220 function be targeted for antimicrobial development?

The essential nature of YE2220 for proper bacterial cell division and virulence, as suggested by studies on the homologous ispA gene in Shigella , makes it a potential target for novel antimicrobial strategies:

• Small molecule inhibitors:

  • Target specific protein-protein interactions between YE2220 and other divisome components

  • Disrupt membrane integration or proper folding of YE2220

  • Interfere with potential enzymatic activities

• Peptide-based approaches:

  • Develop peptides mimicking interaction interfaces

  • Create membrane-penetrating peptides targeting YE2220-specific sequences

• Combination approaches:

  • Target YE2220 in combination with other cell division proteins

  • Develop adjuvants that enhance susceptibility to existing antibiotics

• Screening strategies:

  • High-throughput screens using bacterial growth as a readout

  • Target-based screens using purified recombinant YE2220

  • Phenotypic screens focusing on division defects

• Structure-based drug design:

  • Once structural information becomes available, utilize rational design approaches

  • Virtual screening against predicted binding pockets

The potential advantage of targeting YE2220 lies in its apparent importance for virulence , which might allow for the development of anti-virulence agents that disrupt pathogenesis without directly killing bacteria, potentially reducing selective pressure for resistance development.

What is the evolutionary conservation of YE2220 across bacterial species?

Understanding the evolutionary conservation of YE2220 provides insights into its fundamental importance and potential as a broad-spectrum antimicrobial target:

• Homology across Enterobacteriaceae:

  • YE2220 shares functional homology with the ispA gene product in Shigella flexneri

  • The gene is also referred to as yciB, a designation used in E. coli and other Enterobacteriaceae

• Structural conservation:

  • The hydrophobic nature and membrane localization appear conserved across species

  • Transmembrane domain organization likely maintains similar topology

• Functional conservation:

  • The role in cell division appears conserved between Yersinia and Shigella

  • The connection to virulence may vary in different pathogens

• Evolutionary analysis approaches:

  • Phylogenetic analysis across bacterial phyla

  • Synteny analysis to examine conservation of genomic context

  • Selection pressure analysis to identify critically conserved residues

Comparative genomic analyses could reveal whether YE2220 represents a core bacterial function present across diverse species or is more specialized to certain bacterial lineages. This information would be valuable for understanding the fundamental biology of bacterial cell division and for evaluating the protein's potential as a broad-spectrum drug target.