Recombinant Calycanthus floridus var. glaucus NAD (P)H-quinone oxidoreductase subunit 6, chloroplastic (ndhG)

What is NAD(P)H-quinone oxidoreductase subunit 6 (ndhG) and what is its role in plant physiology?

NAD(P)H-quinone oxidoreductase subunit 6 (ndhG) is a chloroplastic protein that forms part of the NAD(P)H dehydrogenase (NDH) complex in plant chloroplasts. The NDH complex plays critical roles in photosystem I (PSI) cyclic electron transport and chlororespiratory electron transport in higher plants. This protein is encoded by the ndhG gene in the chloroplast genome and contributes to the oxidoreduction of quinones using either NADPH or NADH as electron donors. In the context of plant physiology, the NDH complex helps regulate electron flow during photosynthesis, particularly under stress conditions when linear electron flow might be compromised .

How is the ndhG gene organized in the chloroplast genome of Calycanthus species?

The ndhG gene is encoded in the chloroplast genome of Calycanthus species. In Calycanthus fertilis (closely related to Calycanthus floridus var. glaucus), the complete chloroplast genome has been sequenced and found to be 153,337 bp in length. The genome is circular and colinear with those of tobacco, Arabidopsis, and spinach. The ndhG gene is one of approximately 88 potential protein-coding genes identified in this chloroplast genome. The Calycanthus chloroplast genome contains the highest gene number ever registered in an angiosperm plastome, with a total of 133 predicted genes (115 individual gene species, with 18 genes duplicated in the inverted repeats) .

What are the optimal expression systems for producing recombinant Calycanthus floridus var. glaucus ndhG protein?

The optimal expression system for producing recombinant ndhG protein from Calycanthus floridus var. glaucus is an in vitro Escherichia coli expression system. This approach is particularly effective for transmembrane proteins like ndhG. For efficient purification, the protein is typically expressed with an N-terminal 10xHis-tag, which allows for affinity chromatography using nickel columns .

When designing expression constructs, researchers should consider:

• Codon optimization for E. coli expression

• Inclusion of appropriate fusion tags (such as 10xHis-tag)

• Selection of suitable expression vectors with strong promoters

• Optimization of induction conditions (temperature, IPTG concentration, duration)

• Consideration of detergents for membrane protein solubilization

The recombinant protein can be provided in either liquid form or as a lyophilized powder, with the latter showing extended shelf life (approximately 12 months at -20°C/-80°C compared to 6 months for liquid formulations) .

What purification strategies are most effective for isolating recombinant ndhG protein?

For recombinant ndhG protein with a His-tag, the most effective purification strategy involves nickel affinity chromatography. Specifically:

• Initial Capture: Use nickel nitrilotriacetate (Ni-NTA) columns to capture the His-tagged protein under non-denaturing conditions.

• Stepwise Elution: Employ imidazole for stepwise elution of the protein from the column.

• Buffer Optimization: Tris/PBS-based buffer with 6% Trehalose, pH 8.0 is recommended for maintaining protein stability.

• Quality Control: Confirm purity and integrity using SDS-PAGE and non-denaturing polyacrylamide gel electrophoresis.

• Storage Consideration: Store in aliquots at -20°C/-80°C to avoid repeated freeze-thaw cycles, which can compromise protein integrity .

For heterodimeric constructs or complex protein assemblies, additional purification steps may be necessary, including size exclusion chromatography or ion exchange chromatography to achieve high purity .

How can researchers verify the functional activity of purified recombinant ndhG protein?

To verify the functional activity of purified recombinant ndhG protein, researchers should employ several complementary approaches:

• Enzymatic Activity Assays:

  • Measure NAD(P)H oxidation rates spectrophotometrically

  • Assess quinone reduction capacity using various electron acceptors

  • Determine kinetic parameters (Km and kcat) with both NADPH and NADH as electron donors

• Functional Reconstitution Tests:

  • Incorporate the purified protein into liposomes or nanodiscs

  • Measure electron transport activities in these reconstituted systems

  • Test interaction with other components of the NDH complex

• Protein-Protein Interaction Studies:

  • Use pull-down assays to examine interactions with other subunits of the NDH complex

  • Employ blue native PAGE to identify potential supercomplex formation with photosystem I components

  • Apply sucrose density gradient centrifugation to analyze complex formation

• Structural Verification:

  • Circular dichroism to confirm proper protein folding

  • Limited proteolysis to assess structural integrity

  • Thermal shift assays to evaluate protein stability

How does the NDH complex containing ndhG interact with Photosystem I in chloroplasts?

The NDH complex containing ndhG interacts with Photosystem I (PSI) to form a novel supercomplex in chloroplasts. This interaction has been demonstrated through blue native PAGE analysis and sucrose density gradient centrifugation of thylakoid membrane complexes.

The formation of this NDH-PSI supercomplex is developmentally regulated during chloroplast biogenesis:

• In etiolated seedlings, the NDH complex exists primarily as a 550-kDa monomer

• After 24 hours of illumination, a small portion of the NDH complex shifts to higher molecular weight, indicating initial supercomplex formation

• The NDH-PSI supercomplex is fully assembled after 48 hours of illumination during chloroplast development

This temporal formation pattern suggests that while the NDH complex is present in etioplasts, its interaction with PSI occurs specifically during chloroplast development and requires light. The interaction likely facilitates cyclic electron flow around PSI, which helps balance the ATP/NADPH ratio during photosynthesis under varying environmental conditions .

What is the functional relationship between ndhG and other subunits in the NDH complex?

The ndhG protein functions within the NDH complex alongside several other subunits, including NdhB, NdhD, NdhL, NdhM, and NdhF. Studies using mutants lacking specific NDH subunits have revealed important functional relationships:

• Subunit Dependency: Mutants lacking NdhL and NdhM can still accumulate a pigment-protein complex with slightly lower molecular mass than the complete NDH-PSI supercomplex, suggesting these subunits may not be essential for basic complex formation but contribute to its stability or function.

• Structural Framework: In contrast, the intermediate complex is unstable in mutants lacking NdhB, NdhD, or NdhF, indicating these subunits (including ndhG) form a critical structural framework for the NDH complex.

• Electron Transport Chain: Based on homology to bacterial complex I, ndhG likely participates in the electron transport chain within the NDH complex, potentially interacting with quinones in the membrane.

• Subunit Interactions: The spatial arrangement of subunits suggests ndhG interacts directly with other membrane-embedded subunits to form a functional electron transport pathway .

What evolutionary insights can be gained from studying ndhG in Calycanthus species?

Studying ndhG in Calycanthus species offers valuable evolutionary insights:

• Basal Angiosperm Position: Calycanthus belongs to the Laurales, an ancient line of angiosperms. Phylogenetic analysis suggests this lineage emerged after the split of angiosperms into monocots and dicots, making it valuable for understanding early angiosperm evolution.

• Chloroplast Genome Conservation: The chloroplast genome organization in Calycanthus is colinear with those of tobacco, Arabidopsis, and spinach, suggesting strong evolutionary conservation of plastid genome structure despite divergence times of over 100 million years.

• Gene Content: Calycanthus fertilis (closely related to C. floridus var. glaucus) has the highest gene number ever registered in an angiosperm plastome, with a total of 133 predicted genes, suggesting it may retain ancestral features lost in other lineages.

• NDH Complex Evolution: The presence and conservation of ndhG and other NDH complex genes in Calycanthus provides evidence for the early establishment of the NDH complex in angiosperms and its continued functional importance throughout plant evolution .

How do subunits of NAD(P)H-quinone oxidoreductase function differently with various electron acceptors?

Research on NAD(P)H:quinone oxidoreductase (NQOR) subunit function has revealed intriguing differences in how subunits cooperate depending on the electron acceptor:

This differential behavior provides important mechanistic insights into how ndhG and related proteins may function within electron transport chains, and how their subunit interactions impact substrate specificity and catalytic efficiency .

What methodological approaches can be used to study subunit interactions in protein complexes like those containing ndhG?

To study subunit interactions in protein complexes containing ndhG, researchers can employ several sophisticated methodological approaches:

• Heterodimer Expression and Analysis:

  • Express wild-type/mutant heterodimers with differential tagging (e.g., polyhistidine tag on one subunit)

  • Purify heterodimers using affinity chromatography with stepwise elution

  • Confirm composition using SDS-PAGE, non-denaturing PAGE, and immunoblot analysis

  • Compare kinetic parameters (Km, kcat) with homodimer counterparts

• Blue Native PAGE Analysis:

  • Solubilize membrane complexes using mild detergents (e.g., dodecyl maltoside)

  • Separate intact complexes based on size and charge

  • Perform second-dimension SDS-PAGE for subunit identification

  • Use immunoblotting with antibodies against specific subunits to identify complex components

• Sucrose Density Gradient Centrifugation:

  • Separate protein complexes based on size and density

  • Collect fractions and analyze by Western blotting for specific subunits

  • Identify co-migrating proteins that may form complexes

• Time-Course Analysis During Development:

  • Isolate complexes at different developmental stages

  • Track formation of complexes and supercomplexes

  • Identify sequential assembly patterns and dependency relationships

How can point mutations be used to study the structure-function relationship of ndhG?

Point mutations provide powerful tools for studying structure-function relationships in proteins like ndhG:

• Targeted Mutagenesis Strategy:

  • Identify conserved residues through sequence alignment across species

  • Target residues in predicted functional domains (e.g., binding sites, catalytic centers)

  • Create single amino acid substitutions that alter charge, size, or hydrophobicity

  • Express and purify mutant proteins for comparative analysis

• Functional Assessment:

  • Compare kinetic parameters (Km, kcat) between wild-type and mutant proteins

  • Assess substrate specificity changes with different electron acceptors

  • Measure the impact on complex formation and stability

  • Evaluate effects on interaction with other protein subunits

• Structural Impact Analysis:

  • Use circular dichroism to detect changes in secondary structure

  • Apply limited proteolysis to identify conformational changes

  • Employ thermal stability assays to assess structural integrity

  • Perform in silico modeling to predict structural consequences of mutations

For example, in related NAD(P)H:quinone oxidoreductase studies, a His-194→Ala mutation dramatically increased the Km for NADPH, demonstrating how single amino acid changes can significantly impact substrate binding and catalytic efficiency .

What experimental approaches can be used to study the role of ndhG in cyclic electron flow around Photosystem I?

To investigate the role of ndhG in cyclic electron flow around Photosystem I (PSI), researchers can employ the following experimental approaches:

• Genetic Manipulation:

  • Generate knockout or knockdown lines for ndhG using transplastomic approaches

  • Create point mutations in conserved residues to alter but not eliminate function

  • Complement mutant lines with modified versions of ndhG to test specific hypotheses

• Spectroscopic Measurements:

  • Use chlorophyll fluorescence to measure cyclic electron flow rates

  • Apply P700 absorption spectroscopy to assess PSI redox state changes

  • Implement electrochromic shift measurements to detect proton gradient formation

• Biochemical Complex Analysis:

  • Isolate thylakoid membranes from wild-type and mutant plants

  • Perform blue native PAGE to detect NDH-PSI supercomplex formation

  • Use sucrose density gradient centrifugation to isolate intact complexes

  • Conduct immunoprecipitation with anti-ndhG antibodies to identify interacting partners

• Physiological Assessments:

  • Examine plant growth under different light intensities

  • Test stress responses (drought, high light, temperature extremes)

  • Measure ATP/NADPH ratios in chloroplasts under various conditions

  • Assess photosynthetic parameters using gas exchange measurements

How does the chloroplast NDH complex formation change during plant development and in response to environmental conditions?

The chloroplast NDH complex undergoes significant changes during plant development and in response to environmental conditions:

• Developmental Progression:

  • In etiolated seedlings, the NDH complex exists as a 550-kDa monomer

  • Initial NDH-PSI supercomplex formation begins after 24 hours of illumination

  • Full assembly of the NDH-PSI supercomplex occurs after 48 hours of illumination

  • This developmental pattern indicates light-dependent assembly of the functional supercomplex

• Environmental Response Patterns:

  • Light intensity influences NDH complex abundance, with increased levels under low light conditions

  • Temperature stress (both heat and cold) can trigger upregulation of NDH complex components

  • Drought stress enhances cyclic electron flow, potentially through increased NDH complex activity

  • Nutrient limitations may alter the stoichiometry of electron transport complexes, including the NDH complex

• Tissue-Specific Variations:

  • NDH complex accumulation varies between leaf developmental stages

  • Bundle sheath cells may contain different levels of NDH complex compared to mesophyll cells

  • Root plastids contain NDH complexes with potentially different compositions

  • Reproductive tissues show altered patterns of NDH complex assembly

What are the future research directions in understanding the role of ndhG in plant stress responses?

Several promising future research directions can advance our understanding of ndhG's role in plant stress responses:

• High-Resolution Structural Studies:

  • Obtain cryo-EM structures of the NDH complex containing ndhG

  • Perform cross-linking mass spectrometry to map protein interactions

  • Use hydrogen-deuterium exchange mass spectrometry to identify dynamic regions

  • Develop computational models of electron transport through the complex

• Temporal Dynamics Analysis:

  • Implement real-time monitoring of NDH complex assembly using fluorescent protein fusions

  • Develop rapid isolation techniques to capture stress-induced complex remodeling

  • Use optogenetic approaches to control complex formation and study functional consequences

  • Apply single-molecule techniques to study individual complex behavior

• Integrated Multi-Omics Approaches:

  • Combine transcriptomics, proteomics, and metabolomics to build holistic models

  • Apply systems biology approaches to understand regulatory networks

  • Develop predictive models of how ndhG and the NDH complex respond to different stressors

  • Integrate data across multiple plant species to identify conserved mechanisms

• Translational Applications:

  • Engineer plants with modified ndhG to enhance stress tolerance

  • Develop screening techniques to identify natural variation in ndhG function

  • Explore potential correlations between ndhG variants and environmental adaptation

  • Assess impact of enhanced cyclic electron flow on crop productivity under stress conditions

How does the ndhG protein from Calycanthus floridus var. glaucus compare with homologs from other plant species?

Comparing the ndhG protein from Calycanthus floridus var. glaucus with homologs from other plant species reveals important evolutionary patterns:

Sequence Conservation Table:

Key observations from comparative analysis:

• Conserved Domains: Transmembrane helices show higher conservation than loop regions, reflecting functional constraints

• Phylogenetic Signal: Sequence differences generally reflect established plant phylogeny, with closer relatives showing higher similarity

• Functional Motifs: Critical functional motifs for quinone binding and electron transport are highly conserved across diverse plant lineages

• Basal Angiosperm Position: Calycanthus ndhG shows intermediate features between monocots and other dicots, consistent with its position as a basal angiosperm

What insights can be gained from studying chloroplast genome evolution in basal angiosperms like Calycanthus?

Studying chloroplast genome evolution in basal angiosperms like Calycanthus provides several key insights:

• Genome Architecture:

  • The Calycanthus chloroplast genome (153,337 bp) maintains a quadripartite structure with large single-copy (LSC) and small single-copy (SSC) regions separated by inverted repeats

  • This architecture is remarkably conserved across angiosperms, suggesting strong selective pressure

  • Gene order is largely colinear with tobacco, Arabidopsis, and spinach, demonstrating conservation of synteny over evolutionary time

• Gene Content:

  • Calycanthus chloroplast genome contains 133 predicted genes (115 individual gene species), the highest gene number recorded in an angiosperm plastome

  • This high gene count may represent an ancestral condition, with gene loss occurring in more derived lineages

  • The retention of all ndh genes (including ndhG) suggests their essential functions were established early in angiosperm evolution

• Phylogenetic Implications:

  • Molecular evidence from the complete chloroplast genome supports the emergence of Laurales (including Calycanthus) after the split between monocots and dicots

  • This positioning helps resolve relationships among basal angiosperms, a historically challenging area of plant phylogeny

  • Protein-coding genes from the plastome provide strong phylogenetic signal for understanding early angiosperm diversification

• Unique Features:

  • The Calycanthus chloroplast genome contains a homolog of the mitochondrial ACRS gene, a rare finding that raises questions about gene transfer between organelles

  • This feature may represent an ancestral condition or a unique evolutionary event in the Calycanthus lineage

What are the main challenges in expressing and purifying membrane proteins like ndhG, and how can they be addressed?

Expressing and purifying membrane proteins like ndhG presents several technical challenges that can be addressed with specialized approaches:

• Expression Challenges:

  • Challenge: Low expression levels due to toxicity or membrane insertion limitations

  • Solution: Use specialized expression strains (C41/C43), lower induction temperatures (16-20°C), and inducible promoters with tight regulation

  • Challenge: Protein misfolding and aggregation

  • Solution: Co-express with chaperones, use fusion partners (MBP, SUMO), and optimize growth media composition

• Solubilization Issues:

  • Challenge: Inefficient extraction from membranes

  • Solution: Screen multiple detergents (DDM, LMNG, CHAPS) at various concentrations; consider styrene-maleic acid copolymer (SMA) for native lipid environment preservation

  • Challenge: Detergent-induced destabilization

  • Solution: Include lipids during purification, use glycerol as a stabilizer, optimize buffer composition with specific ions

• Purification Complications:

  • Challenge: Co-purification of contaminating proteins

  • Solution: Implement stringent washing steps, use size exclusion chromatography as a polishing step, consider orthogonal purification approaches

  • Challenge: Protein heterogeneity

  • Solution: Use fluorescence-detection size exclusion chromatography (FSEC) to assess monodispersity, implement thermal stability assays for quality control

• Storage and Stability:

  • Challenge: Loss of activity during storage

  • Solution: Store in small aliquots to prevent freeze-thaw cycles, include cryoprotectants (trehalose, glycerol), consider flash-freezing in liquid nitrogen

  • Challenge: Long-term degradation

  • Solution: For extended storage, lyophilize with appropriate protectants, store at -80°C, and validate activity before use

How can researchers troubleshoot issues with NDH complex assembly and interaction studies?

When troubleshooting issues with NDH complex assembly and interaction studies, researchers should consider these methodological approaches:

• Sample Preparation Problems:

  • Issue: Degradation during isolation

  • Approach: Include protease inhibitors (PMSF, cocktail inhibitors), maintain samples at 4°C, minimize handling time

  • Issue: Dissociation of complexes

  • Approach: Use milder detergents (digitonin instead of DDM), optimize detergent:protein ratios, include glycerol as a stabilizer

• Electrophoretic Analysis Challenges:

  • Issue: Poor resolution in blue native PAGE

  • Approach: Adjust acrylamide percentage, optimize sample:loading dye ratio, ensure proper solubilization

  • Issue: Weak signals in immunoblotting

  • Approach: Verify antibody specificity, optimize transfer conditions for large complexes, consider enhanced chemiluminescence detection

• Interaction Detection Problems:

  • Issue: False negatives in co-immunoprecipitation

  • Approach: Use reversible crosslinking, vary buffer stringency, test different antibodies/orientations

  • Issue: Nonspecific interactions

  • Approach: Include competitive blockers, increase wash stringency gradually, perform reciprocal pull-downs

• Supercomplex Formation Difficulties:

  • Issue: Inconsistent supercomplex detection

  • Approach: Carefully control plant growth conditions, synchronize developmental stages, optimize thylakoid isolation protocols

  • Issue: Poor separation of complexes

  • Approach: Modify gradient conditions in sucrose density centrifugation, extend run times, use step gradients for better resolution

What are the most effective approaches for studying electron transport mechanisms involving ndhG?

To effectively study electron transport mechanisms involving ndhG, researchers should employ these sophisticated approaches:

• Spectroscopic Techniques:

  • Absorbance Spectroscopy: Monitor NAD(P)H oxidation at 340 nm to measure electron flow rates

  • Fluorescence Spectroscopy: Track changes in chlorophyll fluorescence parameters (Fm, Fo, NPQ) to assess cyclic electron flow

  • EPR Spectroscopy: Identify and characterize redox-active centers and electron transport intermediates

• Electrochemical Methods:

  • Potentiometric Measurements: Determine redox potentials of electron carriers within the complex

  • Amperometric Techniques: Measure electron flow rates using artificial electron acceptors

  • Cyclic Voltammetry: Characterize the redox properties of purified ndhG and subcomplexes

• Kinetic Analysis Approaches:

  • Stopped-Flow Spectroscopy: Measure rapid reaction kinetics of electron transfer events

  • Temperature-Dependence Studies: Determine activation energies for electron transport steps

  • pH-Dependence Analysis: Identify proton-coupled electron transfer mechanisms

• Advanced Structural Approaches:

  • Site-Directed Spin Labeling: Introduce spin labels at specific residues to track conformational changes

  • FRET Analysis: Measure distances between labeled components during electron transfer

  • Hydrogen-Deuterium Exchange: Identify dynamic regions during the catalytic cycle

• Computational Methods:

  • Quantum Mechanical Calculations: Model electron transfer pathways and energetics

  • Molecular Dynamics Simulations: Examine protein dynamics during electron transport

  • Brownian Dynamics: Simulate electron tunneling pathways and rates

How can studies of ndhG and the NDH complex contribute to understanding and improving plant stress tolerance?

Studies of ndhG and the NDH complex offer several avenues for understanding and improving plant stress tolerance:

• Drought Stress Resilience:

  • The NDH complex enhances cyclic electron flow (CEF) around PSI during drought stress

  • Increased CEF generates additional ATP without producing excess NADPH

  • This favorable ATP/NADPH ratio helps maintain cellular homeostasis under water limitation

  • Plants with enhanced NDH activity show improved photosynthetic parameters under drought

• Light Stress Protection:

  • NDH-mediated CEF contributes to photoprotection under high light conditions

  • The process helps dissipate excess excitation energy and prevent photodamage

  • ndhG and the NDH complex work alongside other photoprotective mechanisms

  • Engineering optimized ndhG variants could enhance light stress tolerance

• Temperature Stress Adaptation:

  • Both heat and cold stress impact thylakoid membrane fluidity and electron transport

  • The NDH complex helps maintain electron flow under temperature extremes

  • Understanding how ndhG functions under different temperatures could inform crop improvement

  • Natural variation in ndhG across climate gradients may reveal adaptive mechanisms

• Research Applications Table:

These approaches could ultimately lead to crops with enhanced photosynthetic efficiency under stress conditions, contributing to agricultural sustainability in changing climates .

What is the significance of studying basal angiosperms like Calycanthus for understanding plant evolution and adaptation?

Studying basal angiosperms like Calycanthus provides unique insights into plant evolution and adaptation:

• Evolutionary Framework Development:

  • Calycanthus represents an early-diverging lineage (Laurales) after the monocot-dicot split

  • Its genomic features provide a reference point for understanding angiosperm evolution

  • Comparative studies with Calycanthus help polarize character states as ancestral or derived

  • This evolutionary framework informs hypotheses about adaptation and diversification

• Chloroplast Genome Architecture:

  • The chloroplast genome of Calycanthus contains 133 predicted genes, the highest number recorded in angiosperms

  • This high gene content may represent an ancestral condition, suggesting gene loss as a common evolutionary trend

  • The retention of complete gene sets (like all ndh genes) indicates their early importance in plant physiology

  • Understanding which genes are conserved vs. lost helps identify core photosynthetic machinery

• Photosynthetic Adaptation Insights:

  • The conservation of ndhG and other NDH complex components across evolutionary time suggests fundamental importance

  • Studying these genes in basal angiosperms reveals ancestral functions that may be obscured in derived lineages

  • Comparing NDH complex function across diverse lineages illuminates adaptive modifications

  • This evolutionary perspective helps distinguish conserved core functions from lineage-specific adaptations

• Methodological Value:

  • Calycanthus species serve as outgroups for comparative studies within more derived angiosperm lineages

  • Phylogenetic analyses incorporating basal angiosperms provide robust evolutionary hypotheses

  • Understanding ancestral states in Calycanthus helps interpret molecular evolution in crop species

  • These insights can guide biomimetic approaches to engineering improved photosynthesis

How can heterologous expression systems be optimized for functional studies of chloroplast proteins?

Optimizing heterologous expression systems for functional studies of chloroplast proteins like ndhG requires addressing several challenges:

• Expression Host Selection:

  • E. coli Systems: Most accessible but lack post-translational modifications; optimal for basic structural studies

  • Yeast Systems: Provide eukaryotic environment but still lack chloroplast-specific processing

  • Chlamydomonas reinhardtii: Algal system with chloroplast machinery; good for functional studies

  • Tobacco/Arabidopsis Chloroplast Transformation: Ideal for in vivo studies but technically challenging

• Construct Design Optimization:

  • Include transit peptides for chloroplast targeting in eukaryotic systems

  • Consider codon optimization based on the expression host

  • Design fusion tags that minimally impact function (C-terminal tags often preferable)

  • Include TEV or similar protease sites for tag removal

  • Consider expression of minimal functional domains for difficult proteins

• Expression Condition Matrices:

• Functional Validation Approaches:

  • Develop specific activity assays relevant to the protein function

  • Compare kinetic parameters with native counterparts when possible

  • Assess proper folding using circular dichroism or limited proteolysis

  • Verify oligomeric state using analytical ultracentrifugation or native PAGE

  • Test interaction with known partners using co-immunoprecipitation or pull-down assays