Recombinant Squalus acanthias Proteolipid protein DM gamma

What expression systems are available for Recombinant Squalus acanthias Proteolipid Protein DM gamma?

The documented expression system for this protein is E. coli with an N-terminal His-tag . For researchers considering expression system selection, a methodological approach includes:

• Bacterial expression systems:

  • E. coli BL21(DE3) - Provides high yield but may require optimization for membrane proteins

  • Specialized strains like C41/C43(DE3) designed specifically for membrane protein expression

  • Expression parameters: Growth at 37°C to OD600 0.6-0.8, followed by temperature reduction to 16-18°C before induction with 0.1-0.5 mM IPTG

• Vector selection:

  • pET vector systems with T7 promoter for controlled expression

  • Inclusion of N-terminal His-tag for IMAC purification

  • Consider fusion tags like SUMO or MBP for enhanced solubility if initial expression is problematic

• Alternative expression systems:

  • Insect cell expression systems may provide better folding for complex membrane proteins

  • Cell-free expression systems allowing direct incorporation into nanodiscs or liposomes

The choice should be guided by experimental requirements, with E. coli being well-documented for this particular protein .

What are the optimal storage conditions for maintaining protein stability?

To maintain stability of purified Recombinant Squalus acanthias Proteolipid Protein DM gamma, the following evidence-based storage protocol is recommended:

• Lyophilization approach:

  • The protein is typically supplied as a lyophilized powder, providing long-term stability

  • Reconstitution should be performed in deionized sterile water to a concentration of 0.1-1.0 mg/mL

  • Addition of 5-50% glycerol (with 50% being standard) as a cryoprotectant

• Buffer composition:

  • Tris/PBS-based buffer system at pH 8.0

  • Inclusion of 6% trehalose as a stabilizing agent

  • Consider addition of appropriate detergent above critical micelle concentration for membrane proteins

• Storage temperature and handling:

  • Store at -20°C/-80°C upon receipt

  • Aliquoting is necessary to avoid repeated freeze-thaw cycles

  • Working aliquots can be maintained at 4°C for up to one week

• Quality control:

  • Monitor protein integrity after storage by SDS-PAGE

  • Assess functional activity after reconstitution through appropriate assays

This storage protocol maintains protein stability while minimizing aggregation and degradation during freeze-thaw cycles .

What strategies can address low expression yields of this membrane protein?

When encountering low expression yields with Recombinant Squalus acanthias Proteolipid Protein DM gamma, a systematic troubleshooting approach includes:

• Construct optimization:

  • Codon optimization for E. coli expression systems

  • Adjustment of fusion tag position (N-terminal His-tag is documented)

  • Evaluation of alternative promoter systems (T7, tac, araBAD)

  • Incorporation of signal sequences for membrane targeting

• Host strain selection:

  • C41(DE3)/C43(DE3) for membrane protein expression

  • Rosetta strains if rare codons are present in the sequence

  • SHuffle strains if disulfide bond formation is critical

• Expression condition optimization:

  • Temperature series: Test expression at 37°C, 30°C, 25°C, 18°C, 16°C

  • IPTG concentration gradient (0.1-1.0 mM)

  • Induction at different growth phases (early, mid, late log)

  • Extended expression times (overnight or longer) at lower temperatures

• Media modification:

  • Rich media formulations (TB, 2×YT)

  • Addition of glucose (0.5-1%) to suppress basal expression

  • Supplementation with specific amino acids or metabolic precursors

This systematic approach allows identification of optimal conditions for maximal protein yield while maintaining proper folding.

What purification strategy is most effective for obtaining high-purity protein?

A comprehensive purification strategy for His-tagged Recombinant Squalus acanthias Proteolipid Protein DM gamma should include:

• Cell lysis and membrane protein extraction:

  • Mechanical disruption via sonication or high-pressure homogenization

  • Buffer composition: Tris/PBS-based buffer at pH 8.0 with protease inhibitors

  • Detergent selection for membrane solubilization (DDM, LDAO, or C12E8)

  • Gentle extraction conditions to maintain native conformation

• Primary purification via IMAC:

  • Ni-NTA resin loading in batch or column format

  • Sequential washes with increasing imidazole concentrations

  • Elution with 250-300 mM imidazole

  • On-column detergent exchange if required

• Secondary purification steps:

  • Size exclusion chromatography to remove aggregates

  • Ion exchange chromatography if charge-based separation is beneficial

  • Affinity purification with specific ligands if applicable

• Quality control benchmarks:

  • SDS-PAGE analysis to confirm >90% purity as specified

  • Western blot verification with anti-His antibodies

  • Mass spectrometry to confirm protein identity

The purified protein can then be prepared for storage as a lyophilized powder or maintained in Tris/PBS buffer with 6% trehalose as stabilizer .

How can researchers overcome challenges in membrane protein folding and aggregation?

Addressing folding and aggregation challenges with Squalus acanthias Proteolipid Protein DM gamma requires a multi-faceted approach:

• Buffer optimization:

  • Incorporate stabilizing agents: 6% trehalose as documented for this protein

  • Screen multiple detergents at concentrations above their critical micelle concentration

  • Adjust pH conditions (typically 7.0-8.5) to identify optimal stability range

  • Include reducing agents if disulfide-mediated aggregation occurs

• Expression modification strategies:

  • Reduce expression temperature to 16-18°C to slow protein synthesis

  • Co-expression with molecular chaperones (GroEL/GroES)

  • Fusion with solubility-enhancing partners (MBP, SUMO)

• Advanced solubilization approaches:

  • Stepwise detergent exchange during purification

  • Addition of lipids during extraction to stabilize native conformation

  • Reconstitution into nanodiscs or proteoliposomes

• Analytical assessment:

  • Size exclusion chromatography to monitor aggregation states

  • Dynamic light scattering to assess particle size distribution

  • Circular dichroism to verify secondary structure formation

Implementing these strategies can significantly improve protein quality and reduce aggregation, particularly important for structural and functional studies of this membrane protein.

What analytical techniques are most appropriate for confirming protein identity and integrity?

A comprehensive analytical workflow for Recombinant Squalus acanthias Proteolipid Protein DM gamma should include:

• Protein identity confirmation:

  • SDS-PAGE analysis to verify molecular weight (~27 kDa plus tag)

  • Western blotting with anti-His antibodies to confirm the tagged protein

  • Mass spectrometry (MALDI-TOF or ESI-MS) for accurate mass determination

  • Peptide mapping via LC-MS/MS after proteolytic digestion

• Sequence integrity verification:

  • N-terminal sequencing to confirm intact protein

  • Coverage analysis through peptide mapping

  • Verification of the complete 246 amino acid sequence

• Structural integrity assessment:

  • Circular dichroism spectroscopy to evaluate secondary structure

  • Fluorescence spectroscopy to monitor tertiary structure

  • Thermal shift assays to measure stability

  • Limited proteolysis to identify stable domains

• Homogeneity evaluation:

  • Size exclusion chromatography profiles

  • Dynamic light scattering for size distribution

  • Analytical ultracentrifugation to determine oligomeric state

This analytical cascade provides complementary information about protein quality, ensuring reliable results in subsequent experimental applications.

What are the methodological considerations for membrane protein reconstitution?

For successful reconstitution of Recombinant Squalus acanthias Proteolipid Protein DM gamma into membrane-mimetic systems:

• Selection of reconstitution system:

  • Liposomes - suitable for bulk functional studies

  • Nanodiscs - ideal for structural studies with defined size

  • Bicelles - useful for NMR-based structural studies

  • Amphipols - alternative for stabilizing membrane proteins

• Protocol optimization parameters:

  • Detergent removal methods (dialysis, Bio-Beads, cyclodextrin)

  • Lipid composition tailoring (phosphatidylcholine, phosphatidylethanolamine ratios)

  • Protein:lipid ratio optimization (typically 1:50 to 1:200)

  • Buffer composition (Tris/PBS-based, pH 8.0)

• Quality control criteria:

  • Negative stain electron microscopy to confirm homogeneity

  • Dynamic light scattering to assess size distribution

  • Flotation assays to confirm successful reconstitution

  • Circular dichroism to verify structural integrity maintenance

• Functional validation approaches:

  • Accessibility assays to confirm correct orientation

  • Fluorescence-based assays to monitor protein activity

  • Comparison with native membrane behavior

These methodological considerations ensure that the reconstituted protein maintains its native structure and function for subsequent studies.

How can advanced biophysical techniques be applied to characterize this protein?

Advanced biophysical characterization of Squalus acanthias Proteolipid Protein DM gamma requires specialized techniques:

• High-resolution structural analysis:

  • X-ray crystallography (challenging for membrane proteins)

  • Cryo-electron microscopy in detergent micelles or nanodiscs

  • NMR spectroscopy for dynamic structural information

  • EPR spectroscopy with site-directed spin labeling for topology studies

• Membrane topology investigation:

  • Cysteine scanning mutagenesis with accessibility assays

  • Fluorescence resonance energy transfer (FRET) for distance measurements

  • Hydrogen-deuterium exchange mass spectrometry (HDX-MS)

  • Cross-linking mass spectrometry to map protein-lipid interfaces

• Thermodynamic and kinetic characterization:

  • Isothermal titration calorimetry for binding thermodynamics

  • Surface plasmon resonance for interaction kinetics

  • Differential scanning calorimetry for thermal stability

  • Stopped-flow spectroscopy for conformational changes

• Computational analysis integration:

  • Molecular dynamics simulations in lipid bilayers

  • Homology modeling based on related proteolipid proteins

  • Prediction and validation of functional sites

The integration of these complementary approaches provides comprehensive structural and functional insights into this challenging membrane protein.

What experimental approaches can determine the lipid binding properties of this proteolipid protein?

A systematic approach to characterize the lipid binding properties of Squalus acanthias Proteolipid Protein DM gamma includes:

• Direct binding assays:

  • Liposome co-sedimentation with varying lipid compositions

  • Fluorescence anisotropy with labeled lipids

  • Surface plasmon resonance with immobilized protein

  • Isothermal titration calorimetry for binding thermodynamics

• Membrane integration studies:

  • Reconstitution into liposomes of defined composition

  • Flotation assays to confirm membrane integration

  • Freeze-fracture electron microscopy to visualize distribution

  • Accessibility assays to determine topology

• Lipid specificity determination:

  • Lipid overlay assays with different phospholipid species

  • Competition binding assays with various lipids

  • Native mass spectrometry to identify bound lipids

  • Fluorescence spectroscopy to monitor conformational changes

• Structure-function correlation:

  • Site-directed mutagenesis of predicted lipid-binding residues

  • Molecular dynamics simulations to identify stable lipid-protein interactions

  • Comparative analysis with other proteolipid proteins

These methodologies provide complementary information about the lipid interactions that are likely critical for the physiological function of this proteolipid protein in myelin membranes.

How can researchers design experiments to investigate potential interaction partners?

A comprehensive approach to identify protein-protein interactions for Squalus acanthias Proteolipid Protein DM gamma includes:

• In vitro interaction screening:

  • Pull-down assays using His-tagged protein as bait

  • Surface plasmon resonance with immobilized protein

  • Protein-protein crosslinking followed by mass spectrometry

  • Yeast two-hybrid screening with appropriate membrane protein systems

• Proximity-based interaction methods:

  • BioID or APEX2 proximity labeling in heterologous expression systems

  • Fluorescence resonance energy transfer (FRET) with candidate partners

  • Bimolecular fluorescence complementation assays

• Computational prediction and validation:

  • Homology-based prediction from known mammalian proteolipid protein interactors

  • Structural docking with candidate binding partners

  • Co-evolution analysis to identify potential functional partners

• Functional validation of interactions:

  • Co-immunoprecipitation confirmation

  • Mutagenesis of predicted interaction interfaces

  • Reconstitution of protein complexes in artificial membrane systems

  • Functional assays to assess biological relevance of interactions

This systematic approach allows researchers to identify physiologically relevant interaction partners and understand their functional significance in the context of myelin biology.

What functional assays can assess the biological activity of this protein?

To characterize the biological functions of Squalus acanthias Proteolipid Protein DM gamma, researchers can implement:

• Membrane integration and organization assays:

  • Proteoliposome permeability studies

  • Membrane fluidity measurements using fluorescent probes

  • Lipid domain organization analysis

  • Electron microscopy of membrane ultrastructure

• Comparative functional analysis:

  • Functional comparison with mammalian proteolipid proteins

  • Heterologous expression in mammalian cell lines

  • Complementation assays in proteolipid protein-deficient cells

  • Chimeric protein studies to map functional domains

• Biophysical characterization:

  • Ion conductance measurements in planar lipid bilayers

  • Fluorescence quenching to assess transmembrane topology

  • EPR spectroscopy to monitor conformational changes

  • Dielectric spectroscopy for electrical properties

• Advanced imaging techniques:

  • Super-resolution microscopy of labeled protein

  • Atomic force microscopy of membrane organization

  • Cryo-electron microscopy for structural arrangement

  • Live-cell imaging with fluorescent protein fusions

These functional approaches should be selected based on hypotheses about the protein's role in membrane structure, myelin formation, or other potential functions in the dogfish nervous system.

How can this protein be used in comparative evolutionary studies of myelin proteins?

A methodological framework for evolutionary studies using Squalus acanthias Proteolipid Protein DM gamma includes:

• Phylogenetic analysis:

  • Multiple sequence alignment with proteolipid proteins across vertebrate lineages

  • Construction of phylogenetic trees to trace evolutionary relationships

  • Analysis of selection pressure on specific domains

  • Identification of conserved motifs versus species-specific adaptations

• Structural comparison:

  • Comparative modeling of proteolipid proteins from different species

  • Analysis of structural conservation across evolutionary distance

  • Correlation of structural differences with habitat and nervous system complexity

  • Mapping of functional domains to evolutionary conservation patterns

• Functional conservation assessment:

  • Heterologous expression in mammalian myelinating cells

  • Cross-species complementation assays

  • Domain swapping experiments to identify functionally conserved regions

  • Analysis of lipid binding preferences across species

• Experimental design approach:

  • Expression of recombinant proteins from multiple species

  • Standardized functional assays across homologs

  • Controlled lipid environment to normalize membrane interactions

  • Integration of structural and functional data with evolutionary timelines

This systematic approach provides insights into the evolution of myelin proteins from cartilaginous fish to mammals, potentially revealing fundamental aspects of myelin structure and function.

What considerations are important when designing site-directed mutagenesis experiments?

A strategic approach to site-directed mutagenesis of Squalus acanthias Proteolipid Protein DM gamma includes:

• Target selection rationale:

  • Conserved residues identified through multiple sequence alignment

  • Predicted functional residues based on structural modeling

  • Charged or polar residues within transmembrane domains

  • Cysteine residues that may form disulfide bonds

  • Interface residues from protein-protein interaction predictions

• Mutation design principles:

  • Conservative substitutions to maintain structure (e.g., Leu→Ile)

  • Non-conservative substitutions to test function (e.g., Asp→Ala)

  • Cysteine-scanning mutagenesis for accessibility studies

  • Charge reversal to test electrostatic interactions

  • Introduction of reporter groups (fluorophore attachment sites)

• Technical implementation:

  • PCR-based mutagenesis of the expression construct

  • Verification by sequencing

  • Expression screening of multiple mutants

  • Purification using established protocols with His-tag

• Functional analysis framework:

  • Structural integrity assessment (CD spectroscopy, thermal stability)

  • Membrane integration efficiency

  • Lipid binding properties compared to wild-type

  • Oligomerization state analysis

  • Specific activity measurements for each mutation

This comprehensive mutagenesis strategy allows systematic investigation of structure-function relationships in this proteolipid protein.

How can researchers address the challenges of structural determination for this membrane protein?

Overcoming the challenges of structural determination for Squalus acanthias Proteolipid Protein DM gamma requires a multi-technique approach:

• Sample preparation optimization:

  • Detergent screening for optimal protein stability

  • Incorporation into membrane mimetics (nanodiscs, amphipols)

  • Lipid composition optimization to maintain native conformation

  • Construct engineering to remove flexible regions if necessary

• Crystallization strategies:

  • Lipidic cubic phase (LCP) crystallization

  • Antibody fragment co-crystallization to increase hydrophilic surface area

  • In meso crystallization approaches

  • Systematic screening of temperature, pH, and precipitants

• Cryo-EM approaches:

  • Single particle analysis in detergent micelles or nanodiscs

  • Subtomogram averaging in 2D crystals or reconstituted membranes

  • Sample vitrification optimization

  • Data collection parameters for membrane proteins

• NMR methodology:

  • Solution NMR with detergent-solubilized protein

  • Solid-state NMR with reconstituted proteoliposomes

  • Selective isotope labeling to simplify spectra

  • Fragment-based approaches for challenging regions

• Integrative structural biology:

  • Combining low-resolution data from multiple techniques

  • Validation with crosslinking mass spectrometry

  • Computational modeling constrained by experimental data

  • AlphaFold2 prediction with experimental validation

This systematic approach addresses the specific challenges of membrane protein structural determination while maximizing the chances of success.

What approaches can resolve protein aggregation during purification?

To address aggregation of Recombinant Squalus acanthias Proteolipid Protein DM gamma during purification:

• Buffer optimization:

  • Incorporate stabilizing agents like 6% trehalose as documented for this protein

  • Screen detergent type and concentration systematically

  • Adjust ionic strength and pH (typically pH 8.0 is used)

  • Add glycerol (5-50%) to prevent aggregation

• Purification condition modifications:

  • Maintain temperature at 4°C throughout purification

  • Include reducing agents if disulfide-mediated aggregation occurs

  • Perform size exclusion chromatography immediately after IMAC

  • Consider on-column detergent exchange

• Analytical monitoring:

  • Dynamic light scattering to detect early aggregation

  • Size exclusion chromatography profiles to quantify aggregate formation

  • SDS-PAGE under reducing and non-reducing conditions

  • Negative stain electron microscopy to visualize protein particles

• Intervention strategies:

  • Filtration through 0.22 μm membranes to remove large aggregates

  • Ultracentrifugation to pellet insoluble material

  • Addition of arginine (50-100 mM) as aggregation suppressor

  • Mild detergent adjustment during concentration steps

Implementation of these approaches requires systematic testing and optimization based on the specific properties of this proteolipid protein.

How can researchers validate the correct folding of the purified protein?

A comprehensive validation strategy for properly folded Squalus acanthias Proteolipid Protein DM gamma includes:

• Spectroscopic techniques:

  • Circular dichroism to confirm secondary structure content

  • Intrinsic tryptophan fluorescence for tertiary structure assessment

  • FTIR spectroscopy for secondary structure in membrane mimetics

  • Near-UV CD to probe tertiary interactions

• Thermal stability analysis:

  • Differential scanning calorimetry to measure transition temperatures

  • Thermal shift assays with fluorescent dyes

  • Temperature-dependent circular dichroism

  • Aggregation monitoring during thermal denaturation

• Ligand binding verification:

  • Lipid binding assays compared to native protein

  • Protein-protein interaction studies

  • Functional reconstitution in liposomes

  • Ligand-induced conformational changes

• Structural integrity markers:

  • Limited proteolysis patterns of folded versus unfolded protein

  • Accessibility of epitopes in conformational antibodies

  • Cross-linking pattern analysis

  • Disulfide bond formation verification

These complementary approaches provide a thorough assessment of protein folding quality, essential for reliable functional and structural studies.

What quality control benchmarks should be established for batch-to-batch consistency?

To ensure reproducible research with Recombinant Squalus acanthias Proteolipid Protein DM gamma, establish these quality control benchmarks:

• Physical characterization benchmarks:

  • SDS-PAGE profile with >90% purity as specified

  • Size exclusion chromatography elution profile

  • Dynamic light scattering size distribution

  • Mass spectrometry to confirm molecular weight

• Structural quality parameters:

  • Circular dichroism spectrum with characteristic alpha-helical features

  • Thermal stability profile with consistent transition temperatures

  • Consistent secondary structure content across batches

  • Reproducible tryptophan fluorescence emission maximum

• Functional validation metrics:

  • Lipid binding efficiency

  • Membrane reconstitution success rate

  • Oligomerization state consistency

  • Specific activity in functional assays

• Storage stability indicators:

  • Freeze-thaw stability assessment

  • Time-dependent activity retention

  • Aggregation resistance during storage

  • Consistent behavior after reconstitution from lyophilized state

• Documentation standards:

  • Complete record of expression conditions

  • Detailed purification procedure and yields

  • Quantitative QC results for each batch

  • Certificate of analysis with defined acceptance criteria

Establishing these quality control benchmarks ensures reliable and reproducible results across different experiments and research groups.

What are the emerging research directions for Squalus acanthias Proteolipid Protein DM gamma studies?

Current trends suggest several promising research directions for this unique protein:

• Comparative evolution of myelin proteins:

  • Structural and functional comparison with mammalian proteolipid proteins

  • Investigation of functional adaptation in aquatic versus terrestrial vertebrates

  • Analysis of conserved domains across vertebrate lineages

  • Reconstruction of ancestral proteolipid protein functions

• Advanced structural biology approaches:

  • Cryo-EM structure determination in native-like lipid environments

  • Integrative structural biology combining multiple experimental techniques

  • Molecular dynamics simulations in species-specific membrane compositions

  • Structure-based investigation of oligomerization mechanisms

• Functional characterization opportunities:

  • Role in membrane organization and lipid domain formation

  • Potential ion channel or transporter function investigation

  • Interaction with cytoskeletal elements in myelin organization

  • Comparative functional analysis across species

• Biotechnological applications:

  • Development as a model system for membrane protein studies

  • Template for designing stable membrane protein expression systems

  • Application in biomimetic membrane technologies

These emerging directions represent significant opportunities for researchers to contribute to both the specific understanding of this protein and broader principles of membrane protein biology and evolution.

How does research on this protein contribute to broader understanding of membrane proteins?

Research on Squalus acanthias Proteolipid Protein DM gamma contributes to membrane protein biology in several significant ways:

• Evolutionary insights:

  • Identification of conserved features essential for membrane protein function

  • Understanding of evolutionary constraints in membrane protein adaptation

  • Mapping of functional diversification in the proteolipid protein family

  • Bridging the gap between invertebrate and vertebrate membrane protein studies

• Methodological advances:

  • Optimization of expression and purification strategies for challenging membrane proteins

  • Development of reconstitution systems with broader applicability

  • Refinement of structural analysis approaches for membrane proteins

  • Establishment of quality control standards for reproducible research

• Fundamental principles:

  • Elucidation of lipid-protein interaction determinants

  • Understanding of membrane protein folding and stability mechanisms

  • Insights into oligomerization and supramolecular assembly principles

  • Characterization of environment-specific adaptations in membrane proteins

• Translational research potential:

  • Application to understanding human myelin disorders

  • Development of more stable membrane proteins for biotechnology

  • Design principles for membrane protein engineering