Recombinant Xenopus laevis Transmembrane protein C5orf28 homolog

What is Xenopus laevis Transmembrane protein C5orf28 homolog?

Xenopus laevis Transmembrane protein C5orf28 homolog (also known as TMEM267) is a 215-amino acid transmembrane protein encoded by the tmem267 gene. The protein contains characteristic transmembrane domains that anchor it within cellular membranes. Current research indicates that C5orf28 is evolutionarily conserved across vertebrates, suggesting important biological functions. The protein is notable for its genomic relationship with chemokine genes, particularly ccl28, which is adjacent to c5orf28 in both Xenopus and human genomes, although their precise positions have undergone rearrangement during evolution .

What is the amino acid sequence and key structural features of this protein?

The full amino acid sequence of Xenopus laevis C5orf28 homolog is:

MASEMEKADALLHTFSTASAFSSLGLGLFCFVADRVQQATFIQQHDWLRALSDSTTHCVIGMWSWAIVIGLRKRSDFCEVALAGFFASIIDLDHFFLAGSVSLKAATNLQRRPPLHCSTLIPVVALALKFLMQLLRLKDSWCFLPWMLFISWTSHHVRDGIRHGLWICPFGNTAPLPYWLYVVITASLPSVCSLIMCLTGTRQLMTTKHGIHIDV

Structural analysis indicates the presence of multiple transmembrane helices that are critical for proper membrane localization and potential interaction with other proteins, particularly in signaling pathways.

What is the gene name and synonyms for this protein?

The gene encoding this protein has several identifiers and synonyms:

This nomenclature reflects the evolutionary relationship between Xenopus laevis C5orf28 and its homologs in other species, particularly the human ortholog originally identified on chromosome 5 .

What is the evolutionary relationship of C5orf28 between Xenopus and humans?

The evolutionary conservation of C5orf28 between Xenopus and humans is evident in several aspects:

• Syntenic relationships show that ccl28 is adjacent to c5orf28 in both Xenopus and human genomes, although chromosomal rearrangements have occurred through evolution .

• The genomic organization reveals conservation of key exon-intron boundaries, suggesting functional constraints on protein structure.

• While maintaining core structural elements, species-specific variations exist, potentially reflecting adaptation to different physiological requirements.

• Xenopus laevis, being an allotetraploid organism that underwent whole-genome duplication approximately 17-18 million years ago, may possess homeologous copies of c5orf28 in its L and S subgenomes, providing an excellent model for studying subfunctionalization or neofunctionalization .

How is the C5orf28 gene organized in the Xenopus genome relative to chemokine genes?

The c5orf28 gene in Xenopus shows interesting genomic relationships with chemokine genes:

• The gene is positioned adjacent to ccl28 in the Xenopus genome, similar to the arrangement in humans, though specific positional rearrangements have occurred through evolution .

• This conserved synteny suggests functional relationships between c5orf28 and chemokine signaling pathways.

• In contrast to many chemokine genes that show rapid divergence between L and S subgenomes in Xenopus laevis, the retention and conservation of c5orf28 suggest stronger selective pressure maintaining its function .

• The genomic neighborhood of c5orf28 includes genes involved in immune functions, which may indicate coordinated regulation within this functional gene cluster.

What are the optimal conditions for expressing Recombinant Xenopus laevis C5orf28 protein in E. coli?

For optimal expression of Recombinant Xenopus laevis C5orf28 protein in E. coli:

• Expression Vector Selection: Vectors containing T7 or similar strong promoters with N-terminal His-tag facilitate both expression and subsequent purification. The commercially available recombinant protein uses an N-terminal His-tag fusion .

• E. coli Strain Selection: BL21(DE3) or Rosetta strains are recommended, particularly for eukaryotic proteins that may contain codons rarely used in E. coli.

• Culture Conditions:

  • Induction temperature: 18-25°C (lower temperatures may increase soluble protein yield)

  • IPTG concentration: 0.1-0.5 mM

  • Post-induction time: 4-16 hours (overnight expression at lower temperatures often improves yield)

• Media Composition:

  • Rich media (LB, TB, or 2YT) supplemented with appropriate antibiotics

  • Addition of 5-10% glycerol may improve protein solubility

• Considerations for Transmembrane Proteins:

  • Addition of membrane-mimicking detergents during cell lysis

  • Coexpression with chaperones may improve folding

What purification methods are most effective for His-tagged Xenopus C5orf28 protein?

Effective purification strategies for His-tagged Xenopus C5orf28 include:

The commercially available recombinant protein is purified to greater than 90% purity as determined by SDS-PAGE . For membrane proteins like C5orf28, maintaining appropriate detergent concentrations throughout purification is critical to prevent aggregation while preserving native-like structure.

How should the recombinant protein be stored and reconstituted?

For optimal storage and reconstitution of Recombinant Xenopus laevis C5orf28 protein:

• Storage Recommendations:

  • Store lyophilized powder at -20°C/-80°C upon receipt

  • Working aliquots may be stored at 4°C for up to one week

  • Avoid repeated freeze-thaw cycles as they can lead to protein degradation

• Reconstitution Protocol:

  • Briefly centrifuge the vial before opening to bring contents to the bottom

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

  • Addition of glycerol (final concentration 5-50%, with 50% being standard) is recommended for long-term storage at -20°C/-80°C

• Buffer Composition:

  • The protein is typically stored in Tris/PBS-based buffer containing 6% Trehalose at pH 8.0

  • Trehalose acts as a stabilizing agent that helps maintain protein structure during freeze-thaw cycles

• Aliquoting Strategy:

  • Divide reconstituted protein into single-use aliquots to avoid repeated freeze-thaw cycles

  • Consider smaller aliquot volumes based on experimental requirements

What quality control procedures should be implemented?

Comprehensive quality control for Recombinant Xenopus laevis C5orf28 protein should include:

• Purity Assessment:

  • SDS-PAGE analysis (commercial protein shows >90% purity)

  • Western blotting with anti-His antibodies to verify tag presence

  • Mass spectrometry for precise molecular weight determination

• Structural Integrity:

  • Circular dichroism spectroscopy to assess secondary structure elements

  • Limited proteolysis to evaluate protein folding

  • Thermal shift assays to determine protein stability

• Functional Analysis:

  • Binding assays with potential interaction partners

  • Assessment of oligomerization state by native PAGE or analytical size exclusion

• Contaminant Testing:

  • Endotoxin testing for proteins intended for cell culture applications

  • Host cell protein quantification by ELISA

• Batch-to-Batch Consistency:

  • Retention of reference samples from previous successful batches

  • Standardized acceptance criteria for each quality parameter

How does the structure of Xenopus C5orf28 compare to its human ortholog?

The structural comparison between Xenopus and human C5orf28 reveals:

A detailed homology modeling approach would be required to accurately predict three-dimensional structure differences between the orthologs, as no crystal structures are currently available for either protein.

What functional assays can be used to study C5orf28 activity?

Several functional assays can be employed to study C5orf28 activity:

• Protein-Protein Interaction Assays:

  • Co-immunoprecipitation with potential binding partners

  • Yeast two-hybrid screening to identify interactors

  • FRET/BRET assays for live-cell interaction studies

  • Pull-down assays using recombinant His-tagged protein

• Localization Studies:

  • Immunofluorescence microscopy using antibodies against C5orf28 or its tags

  • Subcellular fractionation followed by Western blotting

  • Live-cell imaging with fluorescently tagged C5orf28

• Functional Genomics:

  • CRISPR/Cas9-mediated knockout or knockdown studies in Xenopus

  • Overexpression studies to observe gain-of-function phenotypes

  • Rescue experiments in knockout models

• Expression Analysis:

  • RNA-seq to determine expression patterns across tissues and developmental stages

  • In situ hybridization to visualize spatial expression patterns

  • Quantitative PCR for relative expression level determination

How might C5orf28 interact with the chemokine system in Xenopus?

The potential interaction between C5orf28 and the chemokine system in Xenopus is suggested by several lines of evidence:

• Genomic Organization: The conserved syntenic relationship between c5orf28 and ccl28 in both Xenopus and human genomes suggests potential functional relationships . This genomic proximity may reflect co-regulation or functional interdependence.

• Evolutionary Context: Unlike many chemokine ligands that show rapid divergence, the conservation of c5orf28 suggests it may play a role in homeostatic processes potentially related to chemokine signaling .

• Potential Mechanisms of Interaction:

  • C5orf28 might function as an accessory protein for chemokine receptors

  • It could participate in trafficking or localization of chemokine receptors

  • It may modulate chemokine gradient formation or stability

• Research Approaches: To investigate these potential interactions:

  • Co-expression studies of C5orf28 with ccl28 and its receptor

  • Proximity labeling techniques to identify proteins in close association with C5orf28

  • Functional assays measuring chemokine activity in the presence/absence of C5orf28

What are the best approaches for studying C5orf28 localization in Xenopus cells?

To effectively study C5orf28 localization in Xenopus cells:

• Fluorescent Protein Fusion:

  • Generate constructs expressing C5orf28 fused to fluorescent proteins (GFP, mCherry)

  • Consider both N- and C-terminal fusions to determine which preserves function

  • Use the Xenopus-specific Tg(Dre.gfap:EGFP) transgenic line methodology for tissue-specific expression studies

• Immunofluorescence Microscopy:

  • Develop specific antibodies against Xenopus C5orf28

  • Use His-tag antibodies for the recombinant protein

  • Co-stain with markers for specific cellular compartments (ER, Golgi, plasma membrane)

• Subcellular Fractionation:

  • Separate membrane fractions (plasma membrane, ER, Golgi)

  • Analyze by Western blotting using specific antibodies

  • Compare distribution in different cell types and developmental stages

• Live Imaging in Xenopus Embryos:

  • Microinjection of fluorescently labeled C5orf28 mRNA

  • Time-lapse confocal microscopy to track dynamic localization

  • Correlation with developmental events and cell movements

• Super-resolution Microscopy:

  • STORM or PALM imaging for nanoscale localization

  • Colocalization with potential interaction partners

  • 3D reconstruction of spatial organization

How can C5orf28 protein be used in studying Xenopus development?

C5orf28 protein can be utilized in developmental studies through several approaches:

• Expression Pattern Analysis:

  • Temporal expression profiling across developmental stages using qPCR and Western blotting

  • Spatial expression mapping using in situ hybridization

  • Correlation with known developmental markers and processes

• Functional Perturbation Studies:

  • Microinjection of recombinant protein to assess gain-of-function effects

  • Morpholino-mediated knockdown to study loss-of-function phenotypes

  • CRISPR/Cas9 genome editing to generate stable knockout lines

• Protein Interaction Networks:

  • Identification of stage-specific binding partners

  • Analysis of potential roles in signaling pathways active during development

  • Investigation of interactions with chemokine system components given the genomic association with ccl28

• Regeneration Studies:

  • Assessment of C5orf28 expression in regenerative contexts, such as spinal cord regeneration

  • Potential relationship to the metabolic shifts observed during Xenopus regeneration processes

  • Functional testing in regeneration models using gain/loss-of-function approaches

What are the challenges in crystallizing transmembrane proteins like C5orf28?

Crystallizing transmembrane proteins like C5orf28 presents several significant challenges:

• Protein Extraction and Stability:

  • Maintaining native conformation during extraction from membranes

  • Finding detergents that stabilize the protein without interfering with crystal contacts

  • Preventing aggregation while achieving high protein concentration

• Crystal Packing Obstacles:

  • Limited polar surface area for forming crystal contacts

  • Detergent micelles can hinder protein-protein interactions needed for crystal formation

  • Conformational heterogeneity reducing crystallization probability

• Advanced Approaches:

  • Lipidic cubic phase (LCP) crystallization methods

  • Antibody fragment-mediated crystallization to increase polar surface area

  • Fusion protein approaches (T4 lysozyme fusion) to stabilize flexible regions

• Alternative Structural Methods:

  • Cryo-electron microscopy (cryo-EM) for structure determination without crystallization

  • NMR spectroscopy for dynamic structural information

  • Computational modeling based on homologous proteins

• Protein Engineering Strategies:

  • Removal of flexible regions that may impede crystallization

  • Introduction of thermostabilizing mutations

  • Surface entropy reduction to promote crystal formation

How can gene editing techniques be applied to study C5orf28 function in Xenopus?

Gene editing approaches offer powerful tools for studying C5orf28 function in Xenopus:

• CRISPR/Cas9 System Implementation:

  • Design of guide RNAs targeting conserved exons of c5orf28

  • Microinjection into Xenopus embryos at early cleavage stages

  • Screening for mutations using T7 endonuclease assay or direct sequencing

• Knockin Strategies:

  • Insertion of fluorescent tags for live imaging

  • Introduction of specific mutations to test structure-function relationships

  • Generation of conditional alleles using loxP/Cre systems

• Experimental Design Considerations:

  • Target both L and S homeologs in Xenopus laevis due to its allotetraploid nature

  • Design controls to account for potential genetic compensation

  • Consider tissue-specific knockouts using the Xenopus transgenic methodologies

• Phenotypic Analysis:

  • Developmental timing and morphological assessment

  • Histological examination of affected tissues

  • Molecular profiling using RNA-seq to identify affected pathways

• Functional Rescue:

  • mRNA rescue experiments to confirm specificity

  • Structure-function analysis through domain-specific mutations

  • Cross-species rescue with human ortholog to assess functional conservation

What are the implications of C5orf28's relationship with ccl28 for immune system research?

The genomic relationship between C5orf28 and ccl28 has significant implications for immune system research:

• Evolutionary Significance:

  • The conserved syntenic relationship between c5orf28 and ccl28 in both Xenopus and humans suggests potential functional relationships maintained throughout vertebrate evolution

  • This conservation contrasts with the rapid divergence seen in many other chemokine genes, indicating important selective pressures

• Potential Functional Relationships:

  • C5orf28 might modulate CCL28 expression, secretion, or activity

  • It could serve as a component of signaling complexes involving chemokines

  • The transmembrane nature of C5orf28 suggests it could function as a scaffold or adapter in immune signaling

• Comparative Immunology Applications:

  • Xenopus offers a valuable model for studying the evolution of chemokine systems

  • The allotetraploid nature of Xenopus laevis provides insight into subfunctionalization after genome duplication

  • Comparison of expression patterns between ccl28 and c5orf28 across tissues and developmental stages

• Research Directions:

  • Co-immunoprecipitation studies to identify physical interactions

  • Comparative expression analysis in immune tissues

  • Functional studies in the context of amphibian-specific immune challenges

What are common problems in recombinant expression of C5orf28?

Common challenges in recombinant expression of C5orf28 include:

• Low Expression Yield:

  • Toxicity to host cells due to membrane protein overexpression

  • Codon bias affecting translation efficiency in E. coli

  • Protein instability or rapid degradation

• Protein Insolubility:

  • Formation of inclusion bodies due to improper folding

  • Hydrophobic transmembrane domains causing aggregation

  • Insufficient membrane-mimicking environment

• Troubleshooting Strategies:

  • Optimize expression temperature (typically lower temperatures improve folding)

  • Test different E. coli strains (Rosetta for rare codons, C41/C43 for membrane proteins)

  • Co-express with molecular chaperones

  • Use fusion tags that enhance solubility (MBP, SUMO)

  • Optimize detergent type and concentration for extraction

• Quality Issues:

  • Incomplete translation resulting in truncated products

  • Post-translational modifications absent in bacterial systems

  • Endotoxin contamination affecting downstream applications

How can protein aggregation be prevented during purification?

To prevent aggregation during purification of C5orf28:

• Detergent Selection and Optimization:

  • Screen multiple detergents (DDM, LMNG, Triton X-100)

  • Maintain detergent concentration above critical micelle concentration

  • Consider mixed micelle systems with cholesterol or lipids

• Buffer Optimization:

  • Include stabilizing agents such as glycerol (5-10%) and trehalose (6%)

  • Optimize salt concentration (typically 150-300 mM)

  • Maintain appropriate pH (typically 7.5-8.0 for C5orf28)

• Physical Parameters:

  • Keep samples cold throughout purification (4°C)

  • Minimize exposure to air/surface interfaces

  • Use gentle mixing methods to avoid shear stress

• Purification Strategy:

  • Implement size exclusion chromatography to remove aggregates

  • Consider on-column refolding approaches

  • Use affinity purification conditions that minimize protein-protein interactions

• Storage Considerations:

  • Add stabilizing agents like trehalose as used in commercial preparations

  • Aliquot and flash-freeze to prevent repeated freeze-thaw cycles

  • Consider lyophilization for long-term storage as used in commercial products

What approaches can overcome low protein yield?

To address low yield of Recombinant Xenopus laevis C5orf28 protein:

• Expression System Optimization:

  • Test alternative expression systems (yeast, insect cells) for improved yield

  • Optimize promoter strength and induction conditions

  • Consider codon optimization for the expression host

  • Test different fusion tags and their positions (N-terminal vs. C-terminal)

• Cell Growth and Induction Parameters:

  • Optimize cell density at induction (typically OD600 0.6-0.8)

  • Test various inducer concentrations (0.1-1.0 mM IPTG for E. coli)

  • Extend expression time at lower temperatures (16-20°C)

  • Use enriched media formulations (TB, 2YT)

• Cell Lysis and Extraction Efficiency:

  • Optimize detergent type and concentration for membrane protein extraction

  • Test different lysis methods (sonication, high-pressure homogenization)

  • Include protease inhibitors to prevent degradation

  • Evaluate extraction efficiency through Western blotting

• Purification Recovery:

  • Optimize binding and elution conditions for affinity chromatography

  • Minimize steps to reduce cumulative losses

  • Test different column matrices and flow rates

  • Recover protein from multiple fractions

• Scale-Up Strategies:

  • Increase culture volume while maintaining optimal conditions

  • Consider fed-batch or high-density cultivation methods

  • Implement automated purification systems for consistent recovery