Recombinant Nematostella vectensis Protein ST7 homolog (v1g243132)

What is the Nematostella vectensis Protein ST7 homolog and its significance in research?

The Nematostella vectensis Protein ST7 homolog (v1g243132) is a full-length protein (552 amino acids) identified in the starlet sea anemone (Nematostella vectensis) . This protein is significant for research because Nematostella vectensis has emerged as a critical model organism for comparative genomics and developmental biology . The sea anemone's genome shows remarkable conservation with vertebrates, particularly humans, frogs, and pufferfish, in terms of gene content, synteny, and intron/exon organization . This conservation makes proteins like the ST7 homolog valuable for evolutionary studies and understanding protein function across diverse taxa. The recombinant version typically includes an N-terminal His-tag for purification purposes and is expressed in E. coli expression systems .

How is the recombinant ST7 homolog typically expressed and purified?

The recombinant Nematostella vectensis Protein ST7 homolog is expressed in E. coli expression systems using standard molecular cloning techniques . The methodological approach typically follows these steps:

• Cloning: The coding sequence for v1g243132 is optimized for E. coli expression and cloned into a suitable expression vector containing an N-terminal His-tag.

• Transformation and Expression: The construct is transformed into E. coli (commonly BL21(DE3) or similar strains). Expression is induced using IPTG or auto-induction media under optimized temperature and time conditions.

• Cell Lysis: Bacterial cells are harvested and lysed using either mechanical disruption (sonication, homogenization) or chemical methods (lysozyme treatment) in appropriate buffer systems.

• Purification: The His-tagged protein is purified using immobilized metal affinity chromatography (IMAC), most commonly with Ni-NTA resin. Additional purification steps may include size exclusion chromatography or ion exchange chromatography.

• Quality Control: Purity is assessed using SDS-PAGE (>90% purity) , and protein concentration is determined using Bradford or BCA assays.

• Lyophilization: The purified protein is lyophilized for long-term storage and stability .

This expression and purification protocol yields a pure protein suitable for functional and structural studies.

What storage conditions are recommended for maintaining protein stability?

For optimal stability of the recombinant Nematostella vectensis Protein ST7 homolog, the following storage conditions are recommended:

Repeated freeze-thaw cycles should be avoided as they can lead to protein denaturation and loss of activity . Working aliquots should be maintained at 4°C for up to one week to minimize degradation. The storage buffer (Tris/PBS-based buffer with 6% Trehalose, pH 8.0) is formulated to maintain protein stability during freeze-thaw processes and long-term storage .

How should the lyophilized ST7 homolog be reconstituted for experimental use?

For proper reconstitution of the lyophilized recombinant Nematostella vectensis Protein ST7 homolog, follow this methodological approach:

• Briefly centrifuge the vial before opening to ensure all material is at the bottom of the tube.

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

• Add glycerol to a final concentration of 5-50% for long-term storage (the standard recommendation is 50% glycerol).

• Prepare small aliquots to avoid repeated freeze-thaw cycles.

• For experimental use, dilute the protein in an appropriate buffer system compatible with your specific assay requirements .

This reconstitution protocol ensures maintenance of protein integrity and activity for downstream applications.

What functional assays can be used to characterize the ST7 homolog protein?

Characterizing the functional properties of the Nematostella vectensis ST7 homolog requires multiple complementary approaches:

• Protein-Protein Interaction Studies:

  • Pull-down assays utilizing the His-tag

  • Yeast two-hybrid screening

  • Co-immunoprecipitation with potential binding partners

  • Surface plasmon resonance to determine binding kinetics

• Localization Studies:

  • Immunofluorescence in Nematostella tissues using anti-His antibodies

  • Subcellular fractionation followed by western blotting

  • Expression of fluorescently tagged fusion proteins in heterologous systems

• Functional Complementation:

  • Expression in yeast models lacking endogenous ST7-like proteins

  • Rescue experiments in Nematostella using CRISPR/Cas9-generated knockouts

• Biochemical Characterization:

  • Phosphorylation status analysis using mass spectrometry

  • Lipid binding assays to test membrane interaction properties

  • Enzymatic activity assays if relevant domains are identified

These approaches can be adapted based on sequence homology predictions and known functions of ST7 homologs in other organisms.

How does the ST7 homolog compare to ST7 proteins in other organisms?

Comparative analysis between the Nematostella vectensis ST7 homolog and ST7 proteins from other organisms reveals important evolutionary insights:

The Nematostella genome shows surprising conservation with vertebrates in gene content and organization . This conservation extends to regulatory mechanisms, with enhancers of developmental genes sharing similar histone modification patterns to those found in bilaterians . This suggests that despite moderate sequence homology, functional roles may be more conserved than previously expected.

Comparative studies benefit from the updated genome sequence of Nematostella vectensis that was recently produced using long-read sequencing approaches . This improved genomic context allows better identification of conserved syntenic regions and regulatory elements that might influence ST7 homolog expression and function.

What challenges exist in expressing the full-length ST7 homolog in heterologous systems?

Expressing the full-length Nematostella vectensis ST7 homolog in heterologous systems presents several technical challenges:

• Membrane Protein Expression:
  The ST7 homolog contains multiple transmembrane domains, making it challenging to express in soluble form. Strategies to overcome this include:

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

  • Expression in eukaryotic systems like yeast, insect cells, or mammalian cells

  • Creating truncated constructs lacking transmembrane regions for specific studies

• Codon Optimization:
  Differences in codon usage between Nematostella and expression hosts may necessitate codon optimization to improve expression yields.

• Protein Folding and Stability:
  The complex structure of the ST7 homolog may require specific chaperones or folding conditions to achieve proper conformation. This might be addressed through:

  • Co-expression with molecular chaperones

  • Expression at lower temperatures

  • Addition of stabilizing agents during purification

• Post-translational Modifications:
  If the native protein undergoes post-translational modifications, bacterial expression systems may not replicate these. Alternative strategies include:

  • Expression in eukaryotic systems capable of appropriate modifications

  • In vitro modification after purification if applicable

• Protein Toxicity:
  Overexpression of membrane proteins can be toxic to host cells, requiring:

  • Tight regulation of expression levels

  • Use of inducible promoters

  • Selection of appropriate host strains

How can the His-tagged ST7 homolog be used for protein-protein interaction studies?

The N-terminal His-tagged recombinant Nematostella vectensis ST7 homolog provides an excellent tool for identifying and characterizing protein-protein interactions through multiple methodological approaches:

• Pull-down Assays:

  • Immobilize the His-tagged ST7 homolog on Ni-NTA resin

  • Incubate with Nematostella tissue lysates or recombinant potential interacting partners

  • Wash to remove non-specific binding

  • Elute and analyze binding partners using mass spectrometry or western blotting

• Crosslinking-coupled Pull-down:

  • Perform in vitro crosslinking of the His-tagged ST7 homolog with potential binding partners

  • Purify complexes using Ni-NTA affinity chromatography

  • Identify interaction partners through mass spectrometry analysis

• Surface Plasmon Resonance (SPR):

  • Immobilize the His-tagged ST7 homolog on an NTA sensor chip

  • Measure binding kinetics with potential interaction partners in real-time

  • Determine association and dissociation rates and binding affinities

• Biolayer Interferometry:

  • Immobilize the His-tagged protein on Ni-NTA biosensors

  • Measure biomolecular interactions in real-time

  • Determine kinetic parameters of binding

• Proximity-based Labeling:

  • Create fusion proteins combining the ST7 homolog with proximity labeling enzymes (BioID or APEX2)

  • Express in relevant cellular contexts

  • Identify neighboring proteins through biotinylation and subsequent purification

These approaches can be particularly valuable for identifying conserved interaction partners by comparison with known ST7 interactors from other organisms.

What are potential applications of the ST7 homolog in studying evolutionary conservation of protein function?

The recombinant Nematostella vectensis ST7 homolog serves as a valuable tool for investigating evolutionary conservation of protein function across metazoan lineages:

• Comparative Functional Studies:

  • Heterologous expression in vertebrate cells lacking ST7 to assess functional complementation

  • Structural comparison with vertebrate ST7 proteins to identify conserved functional domains

  • Comparative binding studies with known vertebrate ST7 interaction partners

• Evolutionary Proteomics:

  • Identification of conserved post-translational modification sites across species

  • Analysis of evolutionary rates in different protein domains to identify functionally constrained regions

  • Reconstruction of ancestral protein states through comparative analysis

• Structure-Function Relationships:

  • Generation of chimeric proteins combining domains from cnidarian and vertebrate ST7 homologs

  • Mutational analysis of conserved residues to assess functional importance

  • Crystallographic studies to compare three-dimensional structures across species

• Regulatory Network Conservation:

  • Investigation of whether ST7 homologs participate in similar signaling pathways across diverse taxa

  • Comparison of expression patterns during development in different organisms

  • Analysis of conserved transcriptional regulation mechanisms

These approaches align with findings that Nematostella's genome shows surprising conservation with vertebrates , making it an excellent model for evolutionary studies.

How might the ST7 homolog relate to the regenerative capabilities of Nematostella vectensis?

The potential role of the ST7 homolog in Nematostella vectensis regeneration presents an intriguing research avenue:

• Expression During Regeneration:
  Research has shown that regeneration in Nematostella involves a complex interplay of signaling pathways, including MEK/ERK, Notch, and canonical Wnt signaling . The ST7 homolog may function within these or parallel pathways during the regenerative process. Temporal expression analysis during regeneration could reveal upregulation or specific expression patterns correlating with key regenerative phases.

• Cellular Proliferation and Regeneration:
  Regeneration in Nematostella requires proliferation that begins approximately 12 hours post-amputation, with a proliferative burst at 18-24 hours . If the ST7 homolog influences cell proliferation, it may be particularly relevant during this critical window. Inhibiting its function through various approaches could reveal effects on regenerative capacity.

• Regeneration-Specific Gene Modules:
  Studies have identified differences between embryonic development and regeneration gene expression patterns in Nematostella . The ST7 homolog might belong to regeneration-specific gene modules rather than developmental ones, or vice versa. Comparative analysis of its expression in these two contexts could be informative.

• Potential Involvement in Apoptotic Signaling:
  Apoptosis plays a crucial role in initiating regeneration in Nematostella, occurring shortly after injury in cells near the wound site . The ST7 homolog might participate in apoptotic signaling or in the subsequent activation of regenerative programs.

• Functional Studies During Regeneration:
  Using CRISPR/Cas9 approaches, which have been developed for Nematostella , researchers could generate ST7 homolog knockouts to directly assess its role in regeneration. Alternatively, antibodies against the protein could be used to track its localization during the regenerative process.