Recombinant UPF0283 membrane protein YPTB2265 (YPTB2265)

What is UPF0283 membrane protein YPTB2265 and what organism does it originate from?

UPF0283 membrane protein YPTB2265 is a multi-pass transmembrane protein belonging to the UPF0283 family. It originates from Yersinia pseudotuberculosis serotype I (strain IP32953), a gram-negative bacterium . The protein consists of 353 amino acids with a molecular weight of approximately 39.3 kDa . According to sequence analysis, YPTB2265 is classified as a cell inner membrane protein with multiple membrane-spanning domains .

What are the structural characteristics of the UPF0283 family of proteins?

The UPF0283 family comprises uncharacterized membrane proteins with similar structural features. Based on bioinformatic analyses, these proteins typically contain:

• Multiple transmembrane helices (multi-pass membrane proteins)

• A subcellular localization in the cell inner membrane

• Conserved sequence motifs across different bacterial species

Comparative analysis with other UPF0283 family members shows structural similarities with proteins from various bacterial species, including Proteus mirabilis (PMI1371) and Rhizobium loti (mlr0776) . The structural homology suggests possible conserved functions across different bacterial species, although specific functional roles remain to be fully characterized.

What are the optimal expression systems for recombinant YPTB2265 production?

Several expression systems have been evaluated for YPTB2265 production with varying efficiencies:

How can culture conditions be optimized to improve YPTB2265 expression?

Optimizing culture conditions is crucial for maximizing membrane protein yields. Research indicates several key considerations:

• Growth rate control: The most rapid growth conditions are often not optimal for membrane protein production. Moderate growth rates typically yield better protein expression .

• Harvest timing: It is crucial to harvest cells prior to glucose exhaustion, just before the diauxic shift. This timing significantly impacts membrane protein yields .

• Temperature: Lower induction temperatures (16-25°C) often improve membrane protein folding by slowing down protein synthesis and allowing more time for proper membrane insertion.

• Media composition: Supplementing media with specific components like glycerol (50%) can improve protein stability, as indicated in several recombinant protein preparations .

• Expression inducers: Optimizing inducer concentration and induction timing based on cell density measurements is critical for maximizing yield while minimizing cellular stress.

The differences in membrane protein yields under different culture conditions are not necessarily reflected in corresponding changes in mRNA levels but may be related to differential expression of genes involved in membrane protein secretion and cellular physiology .

What methods are most effective for solubilizing and purifying YPTB2265?

Effective solubilization and purification of membrane proteins like YPTB2265 typically involve:

• Membrane fraction preparation: After cell lysis, the membrane fraction should be separated by ultracentrifugation.

• Solubilization: YPTB2265 can be solubilized using:

  • Mild detergents like n-dodecyl-β-D-maltoside (DDM) or lauryl maltose neopentyl glycol (LMNG)

  • A buffer system containing Tris-based buffer with 50% glycerol, which has been optimized for YPTB2265 stability

• Purification strategies:

  • Affinity chromatography using the appropriate tag (selected during the production process)

  • Size exclusion chromatography to remove aggregates

  • Ion exchange chromatography for further purification if needed

• Quality assessment: SDS-PAGE analysis should confirm purity of ≥85%, which is standard for research-grade recombinant membrane proteins .

• Storage considerations: YPTB2265 should be stored at -20°C for short-term or -80°C for extended storage. Repeated freeze-thaw cycles should be avoided, and working aliquots can be maintained at 4°C for up to one week .

What is known about the membrane topology and structure of YPTB2265?

The membrane topology of YPTB2265 is characterized by multiple transmembrane domains (TMDs). Based on sequence analysis and comparison with other UPF0283 family members:

• YPTB2265 is predicted to be a multi-pass membrane protein with several membrane-spanning segments

• It is localized to the cell inner membrane

• Hydrophobicity analysis suggests the presence of multiple hydrophobic transmembrane regions separated by hydrophilic loops

While a high-resolution three-dimensional structure of YPTB2265 is not currently available in the Protein Data Bank, computational models can be generated using ModBase 3D structure prediction tools, as referenced for similar UPF0283 proteins .

For experimental structure determination, approaches used for similar membrane proteins include:

• X-ray crystallography of protein-detergent complexes

• Cryo-electron microscopy

• Solution NMR for specific domains or fragments

How do polar and charged residues in transmembrane domains affect membrane protein integration?

The presence of polar and charged residues in transmembrane domains has significant implications for membrane protein integration and stability:

• Membrane integration challenges: Transmembrane domains (TMDs) with polar and/or charged residues present challenges for membrane integration . The presence of residues such as serine (S), threonine (T), asparagine (N), glutamine (Q), arginine (R), and lysine (K) in TMDs can reduce the efficiency of membrane insertion.

• Role of membrane insertases: The endoplasmic reticulum membrane protein complex (EMC) and other membrane insertases are particularly important for the integration of proteins containing TMDs with polar/charged residues . Analysis of YPTB2265's sequence reveals several polar and charged residues within predicted transmembrane regions, which may require specialized membrane insertion machinery.

• Experimental evidence from mutagenesis studies: Research has demonstrated that:

  • Converting polar/charged residues to hydrophobic ones (e.g., S→L, R→L) can make EMC-dependent proteins become EMC-independent

  • Conversely, introducing polar residues (e.g., L→N, I→T, M→Q) into hydrophobic TMDs can convert EMC-independent proteins to become EMC-dependent

• Relevance to YPTB2265: Examining the YPTB2265 sequence for polar/charged residues within predicted transmembrane regions can provide insights into potential challenges for its membrane integration and expression.

What advanced techniques can be used to study YPTB2265 structure-function relationships?

Several sophisticated techniques can be employed to investigate the structure-function relationships of YPTB2265:

• Single-molecule forced unfolding experiments:

  • Magnetic tweezers can be used to study membrane protein folding under native-like bicelle conditions

  • This approach has been successfully used to map the folding energy landscape, folding kinetic rate, and folding intermediates of membrane proteins

  • For YPTB2265, this could reveal the cooperative nature of folding and unfolding transitions

• Membrane protein topology mapping:

  • Using paired constraints during folding simulations can enrich the population of near-native models

  • This approach has been validated for membrane proteins with diverse topologies and lengths ranging from 190-300 residues

  • YPTB2265, with its 353 amino acids, would be an appropriate candidate for such analysis

• Mutagenesis studies:

  • Systematic mutagenesis of polar/charged residues within TMDs can help identify critical residues for folding and function

  • Converting polar to hydrophobic residues or vice versa can provide insights into the role of specific amino acids in membrane integration and protein stability

• Membrane insertase dependency analysis:

  • Proteomic analysis comparing membrane protein levels in cells with or without specific membrane insertases

  • This can determine whether YPTB2265 depends on specific membrane insertion machinery like the EMC

How can researchers overcome low expression yields of YPTB2265?

Low expression yields are a common challenge when working with membrane proteins like YPTB2265. Several strategies can help overcome this limitation:

• Optimization of expression constructs:

  • Consider using different affinity tags or fusion partners that can enhance expression

  • Optimize codon usage for the expression host

  • Test different promoter strengths and induction systems

• Host strain selection:

  • Use bacterial strains specifically designed for membrane protein expression (e.g., C41(DE3), C43(DE3), or Lemo21(DE3))

  • Consider bacterial mutants adapted to the production of the target membrane protein

  • Test eukaryotic expression systems if bacterial expression fails

• Culture condition optimization:

  • Grow cells under tightly-controlled conditions in high-performance bioreactors

  • Harvest cells prior to glucose exhaustion, just before the diauxic shift

  • Adjust temperature, pH, and dissolved oxygen levels to optimize membrane protein production

• Membrane proliferation strategies:

  • Induce membrane proliferation to increase the capacity for membrane protein integration

  • This approach has been shown to enhance membrane protein yields in E. coli expression systems

• Co-expression with chaperones:

  • Co-express molecular chaperones that can assist in proper folding

  • Consider co-expression with components of membrane insertase complexes if YPTB2265 contains challenging TMDs with polar/charged residues

What methods can be used to verify correct folding and membrane insertion of YPTB2265?

Verifying the correct folding and membrane insertion of recombinant YPTB2265 is critical for functional studies. Several complementary approaches can be used:

• Subcellular fractionation and localization:

  • Separate membrane fractions from cytosolic components

  • Confirm YPTB2265 presence in the membrane fraction by immunoblotting

  • Compare with known inner membrane markers

• Protease accessibility assays:

  • Limited proteolysis can reveal the accessibility of different protein regions

  • Protected regions likely correspond to membrane-embedded domains

  • Comparison of digestion patterns between native and denatured samples provides insights into folding status

• Detergent solubility profiles:

  • Properly folded membrane proteins show characteristic solubility in specific detergents

  • Misfolded proteins often aggregate or show atypical detergent solubility

  • Test a panel of detergents with varying properties to establish a solubility profile

• Thermostability assays:

  • Correctly folded proteins typically show cooperative unfolding transitions

  • Methods like differential scanning fluorimetry can assess thermal stability

  • Comparative analysis with known properly folded membrane proteins can serve as a benchmark

• Membrane topology validation:

  • Engineered tag accessibility assays

  • Cysteine scanning mutagenesis coupled with labeling reagents

  • These approaches can verify the predicted orientation of transmembrane segments

What are the specific challenges in studying interactions of YPTB2265 with other proteins?

Studying protein-protein interactions involving membrane proteins like YPTB2265 presents unique challenges:

• Maintaining native membrane environment:

  • Interactions may depend on the lipid environment

  • Consider using nanodiscs, bicelles, or native membrane vesicles to preserve the lipid context

  • Single-molecule forced unfolding experiments in bicelle conditions can provide insights into native interactions

• Identifying weakly associated partners:

  • Cross-linking strategies coupled with mass spectrometry

  • Proximity labeling approaches (BioID, APEX)

  • Co-immunoprecipitation with optimized detergent conditions to maintain interactions

• Distinguishing direct vs. indirect interactions:

  • In vitro reconstitution with purified components

  • Yeast two-hybrid membrane systems or split-ubiquitin assays specifically designed for membrane proteins

  • FRET-based approaches to detect direct interactions in membrane environments

• Temporal dynamics of interactions:

  • Real-time binding assays using surface plasmon resonance with membrane mimetics

  • Single-molecule tracking in native membranes

  • Optogenetic approaches to trigger interactions with temporal control

• Functional validation of interactions:

  • Mutagenesis of interaction interfaces identified through structural analysis

  • Assessment of functional consequences when interactions are disrupted

  • Correlation with phenotypic changes in cellular assays

How can researchers study potential roles of YPTB2265 in bacterial physiology and pathogenesis?

Understanding the functional role of YPTB2265 in Yersinia pseudotuberculosis requires multiple complementary approaches:

• Gene knockout and phenotypic analysis:

  • Generate YPTB2265 deletion mutants

  • Assess growth under various conditions (temperature, pH, nutrient limitation)

  • Evaluate stress resistance, biofilm formation, and virulence properties

  • Compare with other UPF0283 family mutants in related species

• Transcriptomic and proteomic profiling:

  • Compare wild-type and YPTB2265 mutant strains under various conditions

  • Identify pathways affected by YPTB2265 deletion

  • Apply quantitative proteomics approaches similar to those used for membrane protein dependency studies

• Interaction network mapping:

  • Identify protein-protein interactions involving YPTB2265

  • Map genetic interactions through synthetic genetic arrays

  • Use proximity-dependent labeling to identify proteins in the same subcellular neighborhood

• Localization studies during infection:

  • Track YPTB2265 localization during bacterial interaction with host cells

  • Assess redistribution under different infection stages

  • Evaluate co-localization with virulence factors

• Structural comparison with homologs:

  • Compare YPTB2265 with homologs in other pathogenic bacteria

  • Identify conserved features that may indicate functional importance

  • Use this information to guide targeted functional studies

What computational tools and approaches are most useful for predicting YPTB2265 function?

Several computational approaches can provide insights into the potential functions of uncharacterized proteins like YPTB2265:

• Sequence-based function prediction:

  • PSI-BLAST for distant homology detection

  • Hidden Markov Model profiles of protein families

  • Analysis of conserved domains and motifs across UPF0283 family members

• Structural bioinformatics:

  • ModBase 3D structure prediction as referenced for UPF0283 proteins

  • Molecular dynamics simulations in membrane environments

  • Prediction of binding sites and functional residues based on structural conservation

• Co-evolution analysis:

  • Direct coupling analysis to identify co-evolving residue pairs

  • These often correspond to physically interacting residues or functionally linked positions

  • This information can guide experimental design for mutagenesis studies

• Genomic context analysis:

  • Examination of conserved gene neighborhoods across bacterial species

  • Identification of operons containing YPTB2265 homologs

  • These associations often provide functional context

• Network-based approaches:

  • Integration of protein-protein interaction data, gene co-expression, and genetic interactions

  • Prediction of function based on the "guilt by association" principle

  • This can place YPTB2265 in specific biological pathways or processes